Vegan Diet

Diet Reference Archive: a diet with no animal foods, often part of a wider ethical commitment

Vegan Diet

A way of eating that leaves out every food of animal origin: meat, poultry, fish, dairy, eggs and honey. People choose it for the animals, for the environment and for their health, and it needs planning, most of all for vitamin B12.

Family: Plant-based and plant-forward diets Promoted by: The Vegan Society and animal welfare, environmental and plant-based health organizations First appeared: 1944, when the word was coined GRADE: Moderate for a small reduction in HbA1c (average blood sugar) in adults with overweight or type 2 diabetes, vegan diets against usual or other diets, over 12 to 26 weeks; published review (Termannsen et al., 2022)

ON THIS PAGE

1. In brief
2. Overview
3. In practice
4. For the coach
5. The evidence (opens on request)
6. Mechanisms (opens on request)
7. Risks, contraindications and myths (opens on request)
8. Key terms
9. Review questions
10. References
11. Evidence rating and review record

The summary and sections 1 to 3 are the short version and are open when the page loads. Sections 4 to 6 hold the research detail, the biology, and the cautions. Each of those opens when you select its heading, and you can read the page without opening them. Back to the Diet Reference Archive index.

In brief

What is it? A way of eating with no animal foods at all: no meat, poultry or fish, and no dairy, eggs or honey either. For many people who follow it, veganism is an ethical commitment that reaches beyond food, and the diet is one part of it.

Does it work? In trials of 12 to 26 weeks, mostly of low-fat vegan diets taught in weekly classes, adults with overweight or type 2 diabetes saw a small fall in average blood sugar and LDL cholesterol compared with their usual diet or another diet; a published review rated the blood sugar result moderate in certainty and the LDL result low. Blood pressure did not clearly change. The trials mainly measured risk factors, and none was large or long enough to show whether the diet prevents heart attacks, strokes or deaths. Long cohort studies link the diet with lower rates of diabetes and of cancer overall, though not of every cancer, but they cannot show cause. In the longer Adventist follow-up, deaths from any cause did not clearly differ between vegans and nonvegetarians.

Is it safe? For adults, the Academy of Nutrition and Dietetics states that an appropriately planned vegan diet can be nutritionally adequate. The caution that matters most is vitamin B12, which comes naturally only from animal foods, so a vegan needs fortified foods or a supplement. Iodine, calcium and vitamin D need planning too. In long cohort studies, vegans had higher rates of fracture than people who ate meat, and in one cohort that higher risk was not seen in vegan women who took both calcium and vitamin D supplements.

Who should not do it without talking to a doctor or dietitian first? Anyone who is pregnant, breastfeeding or planning a pregnancy. Parents feeding a vegan diet to an infant, child or teenager. Older adults, whose protein and bone needs are higher. Anyone taking insulin, a sulfonylurea, blood pressure medication or warfarin. Anyone with kidney disease, osteoporosis or a history of disordered eating.

Related pages: Mediterranean Diet, which has been tested head to head against a vegan diet. The Vegetarian Diet, Whole-Food Plant-Based Diet, Flexitarian Diet and Pescatarian Diet pages cover the rest of the plant-based family. Full list on the archive index.

1. Overview

What you eat

A vegan diet is built entirely from plant foods: vegetables, fruits, whole and refined grains, legumes such as beans, lentils, peas and soy foods (tofu, tempeh, edamame and soy milk), nuts, seeds and plant oils. Many vegans also eat plant milks and yogurts, meat alternatives, and foods fortified with nutrients that plants supply poorly, such as plant milks with added calcium and vitamin D and breakfast cereals or nutritional yeast with added vitamin B12.

The diet itself sets no rules about portions, carbohydrate, fat or calories. What it defines is what is left out. That leaves room for very different diets under the same name. The Academy of Nutrition and Dietetics describes a healthy vegan pattern as one that emphasizes a variety of nutrient-dense whole foods and moderates highly processed foods high in saturated fat, sodium, refined carbohydrate and added sugar (Raj et al., 2026). A diet of fries, white bread, soda and sweets can also be vegan.

What you avoid or limit

The diet removes all meat and poultry, fish and shellfish, dairy foods such as milk, cheese, butter and yogurt, eggs and honey, along with ingredients made from animals, such as gelatin and the milk proteins whey and casein. The Vegan Society, which coined the word, also lists insects among the animal foods vegans avoid (The Vegan Society, n.d.-a). For people who are vegan for ethical reasons, these exclusions are usually firm rules. Others eat this way most of the time and describe themselves as "mostly vegan" or "plant-based," which is a different thing, covered under how clients describe it.

Where it came from

Vegetarian eating is ancient, and the first vegetarian society was founded in England in 1847 (Leitzmann, 2014). The vegan diet as a named practice is much more recent. According to the Vegan Society's own history, in November 1944 Donald Watson and 5 other "non-dairy vegetarians," including Elsie Shrigley, met in England, founded the society and chose the word "vegan," which Watson later described as the first 3 and last 2 letters of "vegetarian." A formal definition of veganism followed from 1949 onward, and the society's current definition has been in use since 1988 (The Vegan Society, n.d.-b).

Professional opinion has changed alongside public interest. In 2016 the Academy of Nutrition and Dietetics stated that appropriately planned vegetarian diets, including vegan diets, were appropriate for all stages of the life cycle, including pregnancy, infancy and childhood (Melina et al., 2016). Its current position, approved in 2025, addresses only adults who are not pregnant or breastfeeding, and states that guidance for younger people and for pregnancy and breastfeeding is outside its scope (Raj et al., 2026). The diet remains uncommon in the United States: in a 2023 national poll, 1 percent of adults said their eating preference was vegan, similar to earlier readings in 2012 and 2018 (Jones, 2023).

Cultural and philosophical context

For the Vegan Society, veganism is not only a diet. Its definition describes veganism as "a philosophy and way of living which seeks to exclude" all forms of exploitation of, and cruelty to, animals "for food, clothing or any other purpose," as far as that is "possible and practicable" (The Vegan Society, n.d.-a). Many vegans therefore also avoid leather, wool, cosmetics tested on animals and entertainment that uses animals. A client who is vegan for these reasons is describing a value, and the diet follows from it.

The reasons people give vary. The Academy lists concern for health, environmental benefits, the ethics of how animals are treated, cost, and cultural and religious practices among the main motivations for vegetarian and vegan eating (Raj et al., 2026). Several religious and philosophical traditions have long encouraged avoiding some or all animal foods (Leitzmann, 2014), and some vegan clients will describe their diet in those terms. This page describes these reasons as reasons people give and does not rate them. It rates only the health claims made for the diet.

Much of the long-term health research on vegans comes from 2 very different groups: Seventh-day Adventist men and women in the United States and Canada, and volunteers in the United Kingdom recruited through general practices, by post, and through advertisements and word of mouth (Abris et al., 2024; Appleby et al., 2016). That background matters when reading the evidence in section 4.

What it claims to do

Claims for the vegan diet come from several directions. The Vegan Society's definition presents animal-free living as being "for the benefit of animals, humans and the environment" (The Vegan Society, n.d.-a). Physicians who promote vegan diets clinically make specific health claims. In a lifestyle medicine textbook chapter, 2 authors from the Physicians Committee for Responsible Medicine, a nonprofit that advocates plant-based diets, wrote that "for both prevention and management, vegan diets have proven particularly useful" for type 2 diabetes, that "for control of body weight and blood pressure, low-fat vegan diets are far superior to typical Mediterranean diets," and that "a vegan diet is surprisingly easy to adopt and maintain" (Barnard & Kahleova, 2023).

Popular claims go further: that a vegan diet prevents or reverses heart disease, prevents cancer, leads to effortless weight loss, provides more energy, or is the only healthy way to eat. Sections 4 and 6 take up the claims research can test. One of the chapter's own claims can be checked directly against the trial it describes: among participants whose blood pressure medication did not change, blood pressure fell more on the Mediterranean diet than on the vegan diet, and the comparison of all participants in the first diet period showed no clear difference (Barnard et al., 2022).

What it gets right

A vegan diet built on whole plant foods lines up with several things the evidence supports well. It is high in vegetables, fruits, legumes, whole grains, nuts and seeds, low in saturated fat and free of dietary cholesterol. The American Heart Association's 2026 dietary guidance reports that eating patterns higher in plant foods and lower in animal products have been associated with lower coronary heart disease risk (Lichtenstein et al., 2026). In trials, vegan diets lowered LDL cholesterol and average blood sugar a little more than comparison diets did (Termannsen et al., 2022).

It also takes seriously things many clients care about: the welfare of animals and the environmental cost of food. Section 2 shows that diets of vegans have a much smaller estimated environmental footprint than diets high in meat. A coach can honor a client's reasons for being vegan, and the healthful core of the diet, without endorsing every claim made for it.

How clients describe it, and what it gets confused with

Clients say "I'm vegan," "I went vegan," "I don't eat anything from animals," "I eat plant-based," "I'm doing Veganuary," "I'm mostly vegan," or "I'm vegan except for honey." "Plant-based" is a phrase easily confused with vegan. It has no standard definition: the Academy uses it for patterns in which animal foods are "mostly or completely excluded" (Raj et al., 2026). A client who says "plant-based" may mean fully vegan or may mean mostly plants with some meat. Ask.

The diet is easily confused with 4 others in this archive. The Vegetarian Diet removes meat, poultry and fish but usually keeps dairy, eggs or both. The Whole-Food Plant-Based Diet is defined by food quality rather than by exclusion, and some versions include small amounts of animal food. The Flexitarian Diet is mostly plant-based with occasional meat. The Pescatarian Diet excludes meat and poultry but includes fish and seafood. Clients may also name the Whole Food Plant-Based Plate, the American College of Lifestyle Medicine's handout, which shows no animal foods at all; that page covers the handout as a teaching tool, and this page covers the eating pattern.

2. In practice

A typical day of eating

Breakfast might be oatmeal cooked with calcium-fortified soy milk and topped with berries and ground flaxseed, or a tofu scramble with peppers, spinach and whole-grain toast. Lunch might be a bean and brown rice burrito with salsa and avocado, or lentil soup with a salad of greens and chickpeas. Snacks might be hummus with carrots, an apple with peanut butter, or a fortified soy yogurt with walnuts. Dinner might be a stir-fry of calcium-set tofu, broccoli and bok choy over rice, or whole-wheat pasta with tomato sauce and white beans. Several of these foods are on the Academy's list of sources of calcium and of the plant omega-3 fat alpha-linolenic acid, such as fortified soy milk, calcium-set tofu, kale, walnuts and flaxseed (Raj et al., 2026).

What makes the day work is planning that does not show on the plate: a reliable source of vitamin B12, a source of iodine such as iodized salt, and enough calcium and vitamin D, each chosen with a clinician or dietitian. Section 6 explains why. The same day can also be built from frozen vegan pizza, fries, sweetened cereal and chips; that is still vegan, but it is not the diet the trials tested.

Cost, products, and who profits

A vegan diet built on beans, lentils, rice, oats, potatoes and seasonal or frozen produce can cost less than a diet built around meat and cheese. The measured data found for this page come from 2 secondary analyses of trials run by the Physicians Committee for Responsible Medicine, which promotes vegan diets; in both, the researchers linked participants' food records to national food prices from the U.S. Department of Agriculture.

In a 16-week trial in adults with overweight, food costs in the vegan group fell from about $9.31 to $7.80 a day, roughly 16 percent, while the control group, who did not change their diet, had no clear change; the difference between groups was $0.90 a day (Kahleova et al., 2023). In a crossover trial, food costs fell by $1.80 a day, or 19 percent, on a low-fat vegan diet and did not clearly change on a Mediterranean diet (Kahleova et al., 2024).

In both analyses, savings on meat and dairy outweighed higher spending on vegetables, legumes and meat alternatives. These are food records from motivated trial participants priced at national averages, not what a family paid at a particular store. The Academy summarizes the evidence as limited research suggesting a vegan diet can cost less, and names the barriers for people with low incomes: food prices, access to stores, limited time, and inadequate equipment for storing and preparing food (Raj et al., 2026).

Who profits depends on which version a client follows. Specialty products, such as plant milks, meat and cheese alternatives and ready meals, are a growing market: the Academy cites a forecast that the global plant-based food market will grow from $11.3 billion in 2023 to $35.9 billion in 2033 (Raj et al., 2026). Supplement makers sell vitamin B12 and multinutrient products for vegans, and the Vegan Society sells its own supplement (The Vegan Society, n.d.-a). Much of the trial research on vegan diets for weight and diabetes has been designed, run and funded by the Physicians Committee for Responsible Medicine, whose president, Neal Barnard, is an author of many of those trials and of the cost analyses described here (Kahleova et al., 2023, 2024). That does not make the findings wrong, but a coach should know it when a client cites them.

Environmental footprint

One British study estimated the footprint of what vegans eat in daily life. It linked the food questionnaires of 55,504 participants in the EPIC-Oxford cohort, who were vegans, vegetarians, fish eaters and meat eaters, to environmental data from 570 life-cycle assessments covering more than 38,000 farms in 119 countries. The diets were measured; the environmental impacts were modeled. Compared with people who ate at least 100 grams of meat a day, the diets of vegans had about 25 percent of the greenhouse gas emissions, about 25 percent of the land use, about 46 percent of the water use, about 27 percent of the water pollution from nutrient runoff and about 34 percent of the estimated biodiversity loss (Scarborough et al., 2023).

The uncertainty around each of those figures is wide, because where and how food is produced varies so much, and the diet data were collected in the 1990s while the environmental data describe food sold in the United Kingdom in 2019 (Scarborough et al., 2023). Within a single trial in the United States, the calculated greenhouse gas emissions of participants' recorded diets fell by 57 percent on a low-fat vegan diet and by 20 percent on a Mediterranean diet, compared with their usual diets; those figures were also modeled from food records, by researchers from the organization that ran the trial (Jayaraman et al., 2026). Within a vegan diet, the footprint still depends on which foods a person chooses and how they were produced.

Cultural fit

A vegan diet fits most easily with cuisines that already build meals around legumes, grains and vegetables, such as the bean, rice and corn dishes of Latin America, the dals and vegetable curries of South Asia, the lentil stews of Ethiopia, and the tofu and vegetable dishes of East Asia. It asks more of food traditions built around meat, dairy, eggs or fish, and of families where shared meals and inherited recipes carry meaning. It can be adapted without losing what defines it by keeping the dish and changing the protein or fat, as one American trial did by building both its vegan and its comparison diet around soul food, the traditional foodways of African Americans in the South (Turner-McGrievy et al., 2023).

For many vegans the harder part is social rather than culinary: family meals, holidays, work events and restaurants where the only vegan option is a side dish. When the reason for the diet is ethical, a vegan client may also carry the weight of being the only person at the table who eats this way, which is part of what a coach can help with.

What makes people stop

A survey of people who stopped, which did not report vegans separately, is described on the Vegetarian Diet page. In the 2-year soul food trial, the share of vegan participants who met the study's adherence criteria was 41 percent at 3 months and 29 percent at 24 months (Turner-McGrievy et al., 2023). In a review of 11 trials, most vegan groups reported high adherence, but almost all of them had weekly or twice-weekly classes, and the authors noted that this level of support "questions long-term feasibility" (Termannsen et al., 2022). In a small 8-week trial in identical twins, the twins assigned to the vegan diet reported lower satisfaction with their diet than their siblings (Landry et al., 2023). What follows is observation, not measured data: clients also describe tiredness, worries about getting enough nutrients, and cost or time when convenience foods are not an option.

What happens when you stop

Most trials of vegan diets ended after 12 to 26 weeks, so evidence beyond that is thin. In a trial of 99 adults with type 2 diabetes, the weight difference between a low-fat vegan diet and a diabetes guideline diet at 22 weeks was no longer clear at 74 weeks, when the vegan group had lost 4.4 kilograms and the comparison group 3.0 kilograms from the start; the difference in average blood sugar was clear only in an analysis that set aside later medication changes (Barnard et al., 2009). In a trial in women with overweight, the vegan group had lost an average of 5.8, 4.9 and 3.1 kilograms from the start at 14 weeks, 1 year and 2 years, against 3.8, 1.8 and 0.8 kilograms in the comparison group, as reported in a later review (Termannsen et al., 2022).

In the 2-year soul food trial, both groups lost a little weight by 12 months and no clear difference between them was detected (Turner-McGrievy et al., 2023). The searches for this page did not identify a study that measured what happens to the health of people after they stop eating vegan. Timing matters for vitamin B12 in a different way: symptoms of B12 deficiency can take several years to appear (National Institutes of Health Office of Dietary Supplements, 2025c), so a vegan who goes without a reliable B12 source may not notice a problem for a long time.

Common variations

The whole-food vegan diet emphasizes minimally processed plant foods; it overlaps with the Whole-Food Plant-Based Diet. The low-fat vegan diet, which limits oils, nuts and other high-fat plant foods, is the version tested in most of the weight and diabetes trials described in section 4 (Termannsen et al., 2022). A low-carbohydrate vegan diet, built on soy, gluten, nuts and plant oils, has been tested in a small number of trials (Guest et al., 2024; Termannsen et al., 2022). The raw vegan diet adds a rule against cooking, the defining rule of the Raw Food Diet. Some people follow a "junk food vegan" pattern of processed vegan products, and some people eat vegan only for a set period or on certain days, which is closer to the Flexitarian Diet. The Fruitarian Diet is an extreme version built mostly on fruit.

3. For the coach

SCOPE OF PRACTICE

A health and wellness coach does not prescribe, adjust, endorse or discourage a vegan diet, and does not diagnose or treat. The coach helps the client understand what they have chosen, notice how it is going, and decide what to do next.

Supplements, and the laboratory tests that show whether they are working, belong to the physician and the registered dietitian. The coach does not recommend a vitamin B12, iodine, calcium, vitamin D, iron or omega-3 supplement or a dose, and does not interpret a laboratory result. A vegan diet needs a registered dietitian or physician involved for anyone who is pregnant, breastfeeding or planning a pregnancy, for any infant, child or teenager, for older adults, and for anyone with kidney disease, osteoporosis, a history of disordered eating, or a medication such as insulin, a sulfonylurea, blood pressure medication or warfarin that a change in eating can affect.

Who does what

The physician

Decides whether a vegan diet raises any medical concern for this person, orders and reads the tests that matter for it, and adjusts medication. For a vegan diet these can include vitamin B12 status (serum B12, and methylmalonic acid or homocysteine), iron studies, vitamin D, and bone density where there is a reason to check it. A pediatric society recommends monitoring vitamin B12 markers in vegan children and adolescents during rapid growth (Verduci et al., 2025). The physician also reviews diabetes and blood pressure medication, since vegan diet trials in type 2 diabetes reported participants needing less diabetes medication (Barnard et al., 2006), and warfarin, whose effect changes with big swings in vitamin K intake (National Institutes of Health Office of Dietary Supplements, 2021). In pregnancy, the obstetric clinician leads.

The registered dietitian

Designs and monitors the individual plan. The Academy describes the dietitian's role as providing meal planning and evidence-based information to clients who follow or are interested in a vegan diet, creating tailored, culturally suitable plans, and assessing intake, signs and symptoms, and laboratory status before recommending specific supplements (Raj et al., 2026). For a vegan client that usually means planning sources of vitamin B12, iodine, calcium, vitamin D, iron, zinc, omega-3 fats and protein, and adapting the diet for pregnancy, childhood, older age, sport or a diagnosed condition such as diabetes or kidney disease.

The health and wellness coach

Helps the client see their own reasons for eating vegan and what they want from it, and test the diet against their values and their actual life: cooking skills, budget, time, family meals, eating out and travel. Builds the habits that make a plan workable, such as shopping, batch cooking and remembering a supplement the clinician recommended. With the client's permission, the coach can share general guidance from recognized authorities, such as the Academy's statement that a vegan diet needs appropriate planning and that vitamin B12 in particular needs a reliable source, and explore what the client wants to do with it. Notices how it is going, including energy, mood and social life, and holds the referral line when a question belongs to a clinician.

What a client bringing this diet needs

Clients bring a vegan diet for very different reasons, and the reason shapes the conversation. A client who is vegan for the animals may need no persuading about the diet at all; what they may want is help eating well within it, handling family pressure, or feeling less alone. A client trying it for health, perhaps after a diabetes or cholesterol result, may be hoping it will fix the problem and may not know what it needs to be safe. A parent may be wondering whether to raise a child vegan.

What the coaching conversation can offer that a search engine cannot is room to sort these apart. The coach does not need to agree or disagree with the client's ethics to support them. The coach's part is to help the client get clear about what they want, build a version of the diet that fits their life, and make sure the parts that belong to a clinician, above all vitamin B12 and the special situations in the scope box, have reached one.

What to ask

• What drew you to eating vegan, and what matters most to you about it?
• What does a usual day of eating look like for you now, and how is it working?
• Who else is part of this with you, such as the people you eat with, your doctor or a dietitian, and what has that been like?

Referral red flags

A client who is pregnant, breastfeeding or planning a pregnancy and eats vegan, or a parent feeding an infant or child a vegan diet, needs the clinician and a dietitian involved; the coach makes sure the client has that care rather than judging whether the diet is adequate. A client who describes fatigue, numbness or tingling in the hands or feet, a sore or swollen tongue, palpitations or pale skin is describing symptoms that can come from vitamin B12 deficiency among many other causes; they can appear without anemia and the nerve damage can become permanent, so they are a reason to see a physician soon, not a diagnosis (National Institutes of Health Office of Dietary Supplements, 2025c). Weight a client loses without meaning to is a reason to involve a clinician, and never a sign that the diet is working.

A client taking insulin, a sulfonylurea or blood pressure medication who plans a substantial change in eating keeps the prescriber informed before making it, which is the client keeping the prescriber in the loop rather than asking permission for every food choice. A possible low blood sugar episode calls for immediate action under the client's own diabetes plan; severe symptoms, or an episode the person cannot manage, call for emergency help; afterward the client tells the prescriber about the episode. A client taking warfarin who is about to change how many leafy greens they eat tells the prescriber first (National Institutes of Health Office of Dietary Supplements, 2021). A client with kidney disease, a past fracture or osteoporosis brings the plan to their care team.

A client whose list of avoided foods keeps growing beyond animal foods, who is frightened of eating anything they did not prepare, who uses veganism to explain skipping meals, or who has stopped eating with other people is worth asking about directly: what each restriction is for, whether it causes distress, whether it is narrowing what they eat, and whether it is getting in the way of daily life. There are ordinary reasons for strict food rules, and ethical veganism is one of them. Where the answers raise a real concern about disordered eating, the coach follows their own referral process, or tells the client's clinician under an existing care plan.

Special populations

Pregnancy and breastfeeding

The Academy's current position does not cover pregnancy or breastfeeding (Raj et al., 2026). A German pregnancy guideline reports that the German Nutrition Society's 2024 position makes no recommendation for or against a vegan diet in pregnancy because data are limited, stresses reliable vitamin B12 supplementation and counseling by qualified professionals, and notes that Switzerland and Austria still do not recommend a vegan diet in pregnancy (Alaze-Hagemann et al., 2026). A 2024 review found only 6 eligible studies; children of vegan mothers had lower birth weight on average (Meulenbroeks et al., 2024), and in one Israeli study of 60 vegan women, the vegan diet was associated with a higher risk of a baby small for gestational age compared with omnivores (Avnon et al., 2021). Infants exclusively breastfed by mothers who eat no animal foods can develop vitamin B12 deficiency early in life (National Institutes of Health Office of Dietary Supplements, 2025c). The searches for this page did not identify a randomized trial of a vegan diet in pregnancy. Planning belongs with the obstetric clinician and a dietitian.

Children and adolescents

A 2025 position paper from the European Society for Paediatric Gastroenterology, Hepatology and Nutrition found the evidence "inconclusive" on whether a strictly vegan diet supports normal growth, found no proven health benefits of a vegan diet in childhood, and recommended that vegan infants, children and adolescents receive regular counseling from a qualified dietitian, be monitored by a pediatrician, and take specific supplements, including vitamin B12 (Verduci et al., 2025). In a Polish study of children aged 5 to 10, the 52 vegan children had a healthier cholesterol profile but were on average about 3 centimeters shorter and had lower bone mineral content and more vitamin B12 deficiency and iron-deficiency anemia than omnivorous children; supplementation resolved the low B12 and vitamin D levels (Desmond et al., 2021). The searches for this page did not identify a randomized trial of a vegan diet in healthy children. Small randomized trials in children with obesity and high cholesterol, such as a 4-week trial of a plant-only diet in 30 child and parent pairs (Macknin et al., 2015) and a 1-year trial described on the Whole-Food Plant-Based Diet page, examined cardiovascular risk factors; they do not establish long-term safety or normal growth. A child's diet belongs to the family and the pediatrician, with a dietitian.

Older adults

Energy needs generally fall with age while needs for some nutrients, such as protein and calcium, may rise, and the Academy suggests at least 1 gram of protein per kilogram of body weight a day for older adults, from plant or animal sources (Raj et al., 2026). Older-adult studies include short controlled-feeding experiments and a 12-week self-selected diet trial. A 10-day crossover comparison of energy- and protein-matched diets in 34 active older adults found no clear difference in muscle protein synthesis, the rate at which muscle builds new protein (Domić et al., 2025); a 3-day high-protein comparison in 19 older adults found similar rates, although 3 vegetarians were placed in the vegan group rather than randomized (Monteyne et al., 2021). In the 12-week trial in 72 adults aged 65 and older, protein intake fell and muscle mass declined in the self-selected vegan group; resistance exercise reduced, but did not eliminate, that decline (Domić et al., 2026). These studies test different diets and durations and do not establish the long-term effects of every appropriately planned vegan diet. Older adults are also more likely to absorb vitamin B12 poorly (National Institutes of Health Office of Dietary Supplements, 2025c). An older client changing to a vegan diet benefits from a dietitian's plan.

Athletes and people with high activity

The Academy states that, for active adults and athletes who want to gain muscle size or strength, plant protein does not appear to limit muscle building when intake reaches at least 1.5 grams of protein per kilogram of body weight a day (Raj et al., 2026). In a 9-day controlled feeding study in 40 active young adults doing resistance exercise, muscle protein building did not differ between vegan and omnivorous diets with the same protein intake (Askow et al., 2025). Only the abstract was available. A sports dietitian can help an athlete meet energy and protein needs.

People taking medication for diabetes, blood pressure, or blood thinning

In a 22-week trial in adults with type 2 diabetes, 43 percent of the vegan group and 26 percent of the comparison group reduced their diabetes medication (Barnard et al., 2006), and in a 12-week trial in adults with type 1 diabetes, total insulin dose fell by about 12 units a day on a vegan diet (Kahleova et al., 2025). Any client taking insulin, a sulfonylurea, blood pressure medication or warfarin who plans a substantial change in eating keeps the prescriber informed before making it. Warfarin needs a steady intake of vitamin K, which leafy greens supply (National Institutes of Health Office of Dietary Supplements, 2021). Metformin can reduce vitamin B12 absorption, which matters more for someone with no animal sources of B12 (National Institutes of Health Office of Dietary Supplements, 2025c).

People with a history of disordered eating

A 2026 review of 24 cross-sectional studies found no clear difference in eating disorder symptoms between people who follow vegetarian or vegan diets and omnivores, with no difference by diet type (Díaz-Goñi, Mesas, et al., 2026). A separate 2026 review of 26 cross-sectional studies found that adults following vegetarian or vegan diets reported more symptoms of orthorexia nervosa, a term for an obsessive focus on eating only foods a person believes are healthy, than omnivores, with vegans and vegetarians alike; the authors cautioned that the studies were of low quality and could not show cause (Díaz-Goñi, Bizzozero-Peroni, et al., 2026). For a person with a history of disordered eating, a diet with firm rules about what is allowed deserves a conversation, and the eating disorder care team belongs in the plan.

Client misconceptions

Four come up most: that vegan automatically means healthy, that vegans cannot get enough protein, that a person who eats well or eats seaweed or fermented foods does not need vitamin B12, and that a vegan diet is proven to reverse heart disease or lengthen life. The short version for the coach is that the diet is only as healthy as the foods in it, that protein is usually adequate in adults but deserves attention in older adults, that B12 needs a reliable source for everyone eating this way, and that the proof for preventing disease is weaker than the claims. Each, with where it came from, is in section 6.

🤝 COACHING CONNECTION

Jasmine went vegan 3 months ago for the animals and says she has never felt more like herself. She also mentions she has been tired lately and wonders whether she should start taking iron. The coach asks what she has noticed about the tiredness and what else has changed for her recently. Jasmine says she has not seen her doctor in a while and does not take any supplements.

The coach asks whether she would like to hear what the Academy of Nutrition and Dietetics says about planning a vegan diet, and she says yes. The coach shares that the Academy describes a vegan diet as nutritionally adequate when appropriately planned and names vitamin B12 as something that needs a reliable source, and that tiredness has many possible causes worth raising with a doctor. Jasmine decides to book a checkup and ask for a referral to a dietitian. The coach did not suggest a supplement, and did not guess at a cause.

4. The evidence

(select the heading to open or close this section)

The evidence comes in 2 kinds that answer different questions. Short trials, most lasting 12 to 26 weeks, show that a vegan diet lowers average blood sugar and LDL cholesterol a little more than usual diets do in adults with overweight or type 2 diabetes, with smaller or unclear differences against other healthy diets. They mainly measured risk factors; the one small trial found that also monitored clinical events was too short to show prevention. Long cohort studies of vegans, almost all from 2 populations, link the diet with lower rates of some diseases and higher rates of fracture, but they cannot show cause; in the longer Adventist follow-up, deaths from any cause did not clearly differ between vegans and nonvegetarians.

This page reports studies that report vegans separately. Studies that pool vegans with vegetarians, and the research on plant-based diet scores, are reported on the Vegetarian Diet and Whole-Food Plant-Based Diet pages.

Evidence from randomized controlled trials

A trial assigns people to a diet by chance and compares them with people assigned to something else, which is the strongest way to test whether the diet itself causes a result. The vegan trials are mostly small and short, mostly in the United States, and mostly tested a low-fat vegan diet eaten without calorie limits, taught in weekly classes with cooking instruction. Many were run by the Physicians Committee for Responsible Medicine.

Three systematic reviews rate them with GRADE. A 2022 review pooled 11 trials with 796 adults who had overweight or type 2 diabetes, lasting 12 to 26 weeks (Termannsen et al., 2022). A 2021 Cochrane review pooled 13 trials of vegan diets for preventing cardiovascular disease, each lasting at least 12 weeks (Rees et al., 2021). A 2024 review for the Academy of Nutrition and Dietetics pooled trials in adults with type 2 diabetes (Guest et al., 2024).

Cardiometabolic outcomes

Average blood sugar. HbA1c is a blood test that reflects average blood sugar over the past 2 to 3 months, reported as a percentage. Across 9 trials with 687 people, vegan diets lowered HbA1c by 0.18 percentage points more than comparison diets, from 0.07 to 0.29 points; the review rated this moderate in certainty, lowered once because the result was imprecise (Termannsen et al., 2022). The fall was larger in people with type 2 diabetes, 0.38 points, than in people with overweight but no diabetes, 0.08 points. The Academy's review found a similar result in type 2 diabetes for its vegan trials, a 0.39-point reduction, from 0.18 to 0.60, also rated moderate (Guest et al., 2024). For a sense of scale, a difference of 0.38 points is roughly the gap between an HbA1c of 7.5 and one of 7.1 percent.

LDL cholesterol. Across 8 trials with 684 people, LDL cholesterol was 0.24 mmol/L lower on vegan diets than on comparison diets, from 0.07 to 0.40 lower, about 9 mg/dL; the review rated this low in certainty, lowered for imprecision and for inconsistency between trials (Termannsen et al., 2022). The comparison matters. The Cochrane review reports moderate-certainty evidence that a vegan diet probably led to a small reduction in LDL cholesterol, 0.22 mmol/L, compared with no or minimal intervention, but probably little or no difference compared with another dietary intervention, 0.05 mmol/L, from 0.21 lower to 0.11 higher (Rees et al., 2021). Against usual eating, a vegan diet lowered LDL; against another healthy diet, the advantage was small or not detected.

The same Cochrane review reports, against no or minimal intervention, a very small fall in HDL cholesterol and a very small rise in triglycerides, which the authors note are in the opposite direction to that expected (Rees et al., 2021). In the 2022 review, neither HDL cholesterol nor triglycerides differed clearly (Termannsen et al., 2022).

Blood pressure. Across 8 trials with 466 people, systolic blood pressure was 1.28 mm Hg higher on vegan diets, from 1.54 lower to 4.11 higher, and diastolic was 0.54 mm Hg higher; no clear difference was detected, and the review rated the estimates moderate (Termannsen et al., 2022). The Cochrane review likewise found no clear effect on blood pressure against no or minimal intervention, at low certainty (Rees et al., 2021). Direct comparisons with a Mediterranean diet are described under Head to head.

Three cautions apply to these pooled results. Comparison diets differed in more than animal foods: 4 of the 8 active comparison diets limited calories while the vegan diets did not, and in 4 trials the vegan groups ate less energy, which the review authors say may explain part of the effect (Termannsen et al., 2022). Most trials gave intensive support. And the 2022 review's study table lists the vegan versus Mediterranean crossover trial as 2 periods of 26 weeks, while the trial report describes 16-week periods (Barnard et al., 2022); this concerns the table's label rather than the pooled numbers.

Two trials outside those reviews add to the picture. One 2-year trial, the Nutritious Eating with Soul study, randomized 159 African American adults with overweight or obesity to a vegan or a low-fat omnivorous diet, both built on soul food, with classes for 2 years. At 12 months, when 121 of the 159 (76 percent) were measured, no clear difference was detected in weight, total cholesterol or LDL cholesterol; the authors note that the COVID-19 pandemic began during the trial and may have weakened it (Turner-McGrievy et al., 2023). In an 8-week trial in 22 pairs of healthy identical twins, with 21 pairs analyzed, the twin assigned to a healthy vegan diet had LDL cholesterol 13.9 mg/dL lower, from 2.4 to 25.3 lower, than the twin assigned to a healthy omnivorous diet (Landry et al., 2023).

Cancer

The searches for this page did not identify a randomized trial of a vegan diet that measured cancer diagnoses. Evidence on vegan diets and cancer comes from cohort studies, described below.

Body weight, as measured

Across 10 trials with 697 people, measured body weight fell 4.1 kilograms more on vegan diets than on comparison diets, from 2.4 to 5.9 kilograms; the review rated this moderate, lowered once because results differed widely between trials (Termannsen et al., 2022). The difference was 7.4 kilograms against people who kept their usual diet and 2.7 kilograms against people assigned another diet.

In a 6-month trial that randomized 63 adults to 5 diets, 12 of them to a vegan diet, with 50 completing it, the vegan group lost 7.5 percent of body weight against 3.1 percent in an omnivorous group that had fewer meetings (Turner-McGrievy et al., 2015). In the 2-year soul food trial, both groups lost about 2 kilograms by 12 months and no clear difference was detected (Turner-McGrievy et al., 2023). This archive reports weight as something studies measured, not as a goal.

Mortality

Vegan trials mainly measured risk factors. One small trial randomized 100 people with coronary artery disease to a vegan or an American Heart Association diet for 8 weeks and monitored deaths, heart attacks, strokes or transient ischemic attacks, and repeat heart procedures; the only events were 2 probable transient ischemic attacks, brief stroke-like episodes, both on the American Heart Association diet. The authors state that the trial was not powered to compare these events (Shah et al., 2018). The Cochrane review, which included only trials of at least 12 weeks, found that none of its 13 trials reported clinical event outcomes (Rees et al., 2021), and the Academy's review identified no trial in adults with type 2 diabetes that examined cardiovascular disease, kidney disease or mortality (Guest et al., 2024).

Safety and nutrient status in trials

Most trials did not report adverse events. In the 2022 review, 3 of 11 trials did, and none found treatment-related serious events (Termannsen et al., 2022); the Cochrane review reports that adverse events in 4 trials were absent or minor (Rees et al., 2021). In the 2022 review, 7 of the 11 vegan groups were given B12, at 50 to 1,000 micrograms a day, so most of these trials tested vegan diets with B12 supplied (Termannsen et al., 2022). In the 8-week twin trial, blood B12 did not differ clearly between groups, which the authors attribute to stored B12 and note that long-term vegans are typically encouraged to take a supplement (Landry et al., 2023).

Evidence from long-term prospective cohort studies

A cohort study follows people who already eat a certain way and records what happens to them. It can show that a pattern goes with an outcome; it cannot by itself show that the pattern caused it. Vegetarians and vegans in these studies tend to differ from meat eaters in other ways too, such as smoking less and exercising more (Abris et al., 2024).

Two cohorts supply most of the evidence on vegans. The Adventist Health Study 2 recruited about 96,000 Seventh-day Adventists in the United States and Canada, and its latest mortality analysis included 88,400; in this cohort, vegans were people who ate no animal foods as often as once a month (Abris et al., 2024). EPIC-Oxford and the earlier Oxford Vegetarian Study recruited about 60,000 people in the United Kingdom, including about 2,200 vegans (Appleby et al., 2016). Both measured diet with questionnaires, and both have small numbers of vegans, so their vegan results are often imprecise.

Cardiometabolic outcomes

The Academy's review of systematic reviews summarizes the evidence for vegans in the general population separately from vegetarians as a whole. For vegans, it concludes with low certainty that there may be no difference in rates of cardiovascular disease, coronary heart disease or stroke compared with nonvegetarians, and it rates the evidence on heart attack, cardiovascular death and new type 2 diabetes as very low, or uncertain (Raj et al., 2026). That is weaker than its conclusion for vegetarian diets including vegans, taken together, which the Vegetarian Diet page reports.

Individual cohorts show why. In the British cohorts, deaths from coronary heart disease were not clearly different in vegans, a hazard ratio of 0.85, from 0.51 to 1.44, based on only 14 deaths among vegans (Appleby et al., 2016). In the British cohorts, deaths from stroke and other cerebrovascular disease were higher in vegans, 1.63, from 0.98 to 2.69, based on 19 deaths; the authors wrote that the wide confidence intervals precluded any clear conclusions (Appleby et al., 2016).

For diabetes, over 2 years in the Adventist cohort, 0.54 percent of vegans and 2.12 percent of nonvegetarians reported a new diagnosis; after adjustment, including for body mass index, vegans had lower odds of diabetes, an odds ratio of 0.38 (Tonstad et al., 2013). Those are crude proportions and odds from a self-reported outcome, not time-to-event estimates.

Cancer

A 2026 meta-analysis combined the vegan results from 3 cohort studies reported in 2 publications, from the Adventist Health Study 2 and the British cohorts, with 141,115 participants and 10,562 cancers, and found a 23 percent lower rate of cancer overall in vegans than nonvegetarians, a relative risk of 0.77, from 0.70 to 0.85; with further adjustment for body mass index it was 0.82 (Aune et al., 2026). For specific cancers the estimates were imprecise: 1.02 for colorectal cancer, 0.80 for breast cancer and 0.87 for prostate cancer, each with an interval that includes no difference.

Using the World Cancer Research Fund's grading criteria, the authors graded the evidence that a vegan diet lowers total and breast cancer risk as "limited-suggestive," and for colorectal and prostate cancer as "limited-no conclusion" (Aune et al., 2026). An earlier meta-analysis reached a similar total cancer estimate for vegans, 0.85, from a limited number of studies (Dinu et al., 2017).

A newer pooled analysis of 9 cohorts, with 8,849 vegans, reported higher colorectal cancer incidence in vegans than in meat eaters, a hazard ratio of 1.40, from 1.12 to 1.75, based on 93 cases. The association weakened and was no longer clear after excluding the first 4 years of follow-up, 1.25, from 0.95 to 1.64, but remained in never smokers, 1.67, from 1.28 to 2.18. The authors urge caution because cases were few, and the Adventist and British cohorts supplied most of its vegans, so it does not independently confirm the earlier results. These findings do not prove that a vegan diet causes or prevents colorectal cancer, and Aune's grading did not include them (Dunneram et al., 2026).

Body weight, as measured

In a cross-sectional analysis of 37,875 EPIC-Oxford participants, average body mass index adjusted for age was lowest in vegans, 22.49 in men and 21.98 in women, and highest in meat eaters, 24.41 and 23.52; differences in macronutrient intake accounted for about half of the gap (Spencer et al., 2003). That is a single measurement in people who chose their diets, not evidence that switching to a vegan diet changes weight over time.

Mortality

The longer Adventist Health Study 2 follow-up, a median of about 11 years, found no clear overall difference in deaths among vegans and nonvegetarians: a hazard ratio of 0.99, from 0.92 to 1.06, based on 1,008 vegan deaths. Results differed by sex and age. In men, the hazard ratio was 0.72, from 0.58 to 0.88, at age 65 and 1.07, from 0.95 to 1.21, at age 85; in women it was 0.98, from 0.89 to 1.08, although the difference between men and women was not statistically significant (Abris et al., 2024). The British cohorts reported 1.14, from 0.97 to 1.35, for the 2,228 vegans compared with regular meat eaters, based on 166 vegan deaths before age 90 (Appleby et al., 2016).

Both cohorts compared vegans with people from similar backgrounds who ate meat: a health-conscious Adventist population in one, and what the British authors call comparable nonvegetarians in the other (Abris et al., 2024; Appleby et al., 2016). A 2023 umbrella review rated an earlier pooled estimate from 2 studies, 0.87, from 0.75 to 1.01, as low certainty; it came before the longer Adventist follow-up (Selinger et al., 2023). These observational findings do not establish that vegan diets lengthen or shorten life.

Bone health and fractures

Fracture is a consistent risk signal in the cohort evidence. The Academy lists higher fracture risk and lower bone mineral density among potential harms for vegans, rating the evidence low and very low (Raj et al., 2026). In EPIC-Oxford, among 54,898 participants followed for an average of 17.6 years, vegans had more than twice the rate of hip fracture of meat eaters after adjustment, including for body mass index: a hazard ratio of 2.31, from 1.66 to 3.22, based on 41 hip fractures among vegans. That works out to about 15 more hip fractures for every 1,000 people over 10 years. Vegans also had more fractures overall, 1.43, and more leg fractures; adjusting for calcium and protein intake weakened the associations only slightly (Tong et al., 2020).

In the Adventist cohort, among 34,510 white women and men aged 45 and older, vegan women had a higher rate of hip fracture than nonvegetarian women, 1.55, from 1.06 to 2.26, while vegan men did not differ clearly. Among women, the higher rate was seen in vegans who took neither calcium nor vitamin D supplements, 2.99, from 1.54 to 5.82, and not in vegans who took both, 0.84, from 0.42 to 1.66 (Thorpe et al., 2021). The case counts printed for the group taking both supplements do not add up in a way that fits the other columns, so this page reports only the hazard ratios. A 2025 meta-analysis of 4 cohorts estimated a 75 percent higher hip fracture risk in vegans, 1.75, from 1.17 to 2.63, and rated the evidence very low certainty because of serious risk of bias, inconsistency and imprecision (Ballarin et al., 2025).

Highlighted studies

These 4 studies carry the most weight for this page. Each one is described in the table so a reader can judge it without opening the paper.

On a narrow screen, scroll the table sideways to see every column.

Highlighted studies for the Vegan Diet

Study	Design	Sample size	Duration	Finding	The limitation that matters
Termannsen et al., 2022	Systematic review and meta-analysis of randomized controlled trials, rated with GRADE	11 trials, 796 adults with overweight or type 2 diabetes	12 to 26 weeks	Against usual or other diets: HbA1c 0.18 points lower (moderate); LDL 0.24 mmol/L lower (low); weight 4.1 kg lower (moderate); blood pressure not clearly different (moderate)	Comparison diets differed in more than animal foods, most trials gave intensive support, and none lasted beyond 26 weeks
Turner-McGrievy et al., 2023, the Nutritious Eating with Soul study	Randomized controlled trial	159 African American adults with overweight or obesity randomized; 121 measured at 12 months	2 years, primary results at 12 months	No clear difference in weight, total cholesterol or LDL cholesterol between a vegan and a low-fat omnivorous soul food diet at 12 months	Only about a third of the vegan group met the adherence criteria at 12 months, and the pandemic disrupted the classes
Abris et al., 2024, Adventist Health Study 2	Prospective cohort	88,400 Seventh-day Adventists; 1,008 deaths among vegans	Median about 11 years	Death from any cause: hazard ratio 0.99 (0.92 to 1.06) in vegans against nonvegetarians; in men, lower at age 65 but not at 85	A health-conscious religious community, its nonvegetarians included, with diet measured once at the start
Tong et al., 2020, EPIC-Oxford	Prospective cohort	54,898 adults, including 1,982 vegans at the start	Average 17.6 years	Hip fracture: hazard ratio 2.31 (1.66 to 3.22) in vegans against meat eaters, about 15 more per 1,000 people over 10 years	Only 41 hip fractures among vegans, and diet was recorded at only 2 points, at the start and about 14 years later

Head to head

Against a Mediterranean diet. In a crossover trial, 62 adults with overweight followed a low-fat vegan diet and a Mediterranean diet modeled on the PREDIMED trial for 16 weeks each, in random order, with a 4-week break between. Weight fell 6.0 kilograms on the vegan diet and did not change on the Mediterranean diet, and among participants who did not change medication, LDL cholesterol fell 15.3 mg/dL on the vegan diet with no significant change on the Mediterranean diet. Among 41 participants whose blood pressure medication did not change, systolic pressure fell 9.3 mm Hg on the Mediterranean diet and 3.4 mm Hg on the vegan diet. Carryover, an effect of the first diet lingering into the second period, affected the all-participant systolic analysis; the first-period comparison did not show a clear between-diet difference (Barnard et al., 2022). The trial was run by the Physicians Committee for Responsible Medicine.

A 12-week trial randomized 90 adults with overweight or obesity to 5 diets, including separate vegan and Mediterranean groups of 18 people each; 85 completed it. It did not detect clear differences between groups in blood sugar, insulin, cholesterol or blood pressure, and groups this small over 12 weeks cannot show that the diets are equivalent (Wiśniewska et al., 2025). The Mediterranean Diet page describes that diet's own trials.

Against a vegetarian diet. In a 12-week trial in adults with type 2 diabetes, a low-carbohydrate vegan diet and a lacto-ovo vegetarian diet both lowered HbA1c, with no clear difference between them, 0.10 points, from 0.22 lower to 0.02 higher, as reported in the Academy's review (Guest et al., 2024). The Vegetarian Diet page covers vegetarian diets in full.

Against other plant-based and omnivorous diets. In the 6-month trial of 5 diets, weight loss in the vegan group was greater than in the omnivorous, semi-vegetarian and pescatarian groups (Turner-McGrievy et al., 2015). Against a healthy omnivorous diet in identical twins, the vegan diet lowered LDL cholesterol more over 8 weeks (Landry et al., 2023), and against a low-fat omnivorous diet built on the same cuisine, no clear difference was detected at 12 months (Turner-McGrievy et al., 2023). The searches for this page did not identify a trial comparing a vegan diet directly with the DASH Diet.

Against a ketogenic diet. In a 4-week inpatient crossover study at the National Institutes of Health, 21 adults were randomized to the order of 2 diets offered for 2 weeks each with as much food as they wanted: a low-fat diet made only of plant foods and an animal-based ketogenic diet. One person withdrew after low blood sugar on the ketogenic diet. Among the 20 who completed both, energy intake was about 689 calories a day lower on the plant-only diet (Hall et al., 2021). The study was designed to test a theory about carbohydrate and appetite, not to compare the diets for long-term health; the Ketogenic Diet page describes it and the published debate about its design.

Where the evidence is absent

The documented searches for this page did not identify a vegan diet trial that measured cancer diagnoses or was large and long enough to compare heart attacks, strokes or deaths; the one trial found that monitored such events lasted 8 weeks (Shah et al., 2018), and almost all trials lasted 6 months or less. They did not identify a randomized trial in pregnancy, in breastfeeding or in healthy children. The evidence on nutritional adequacy and growth in otherwise healthy vegan children is largely observational and was judged inconclusive on growth (Verduci et al., 2025). Small randomized trials in children with obesity or high cholesterol have examined cardiovascular risk factors; they do not establish long-term safety or normal growth (Macknin et al., 2015). Older-adult studies include short controlled-feeding experiments and a 12-week self-selected diet trial, described under special populations in section 3.

Most cohort evidence comes from 2 populations, Seventh-day Adventists and British volunteers, so it may not describe vegans elsewhere. Cohorts mostly measured diet once and could not judge the quality of vegans' diets (Aune et al., 2026). The fracture findings about calcium and vitamin D supplements are observational and do not establish that supplementation prevents fractures (Thorpe et al., 2021). Trials of particular vitamin B12 delivery methods in vegans exist, such as a 12-week trial of B12-fortified toothpaste (Siebert et al., 2017), but they do not answer that fracture question.

5. Mechanisms

(optional reading; select the heading to open or close this section)

This section explains how the diet is thought to work in the body. You can skip it. Nothing in the coaching sections depends on it.

Established mechanisms

Why vitamin B12 has to be planned. Vitamin B12 is not naturally present in plant foods; its natural food sources are limited to animal foods, and some plant foods, such as many breakfast cereals and nutritional yeasts, are fortified with it (National Institutes of Health Office of Dietary Supplements, 2025c). A diet with no animal foods therefore supplies almost none unless foods are fortified or a supplement is taken.

The body absorbs B12 with the help of intrinsic factor, a binding protein secreted by cells in the stomach, and absorption is limited: about half of a dose under 1 to 2 micrograms is absorbed, but only about 2 percent of a 500-microgram dose (National Institutes of Health Office of Dietary Supplements, 2025c). Deficiency causes a type of anemia with large red blood cells and can damage nerves, sometimes before any anemia appears (National Institutes of Health Office of Dietary Supplements, 2025c).

Why LDL cholesterol falls. A vegan diet contains no dietary cholesterol and usually much less saturated fat, and it is high in fiber. The authors of the 2022 trial review explain the fall in LDL cholesterol by these differences, with fiber slowing the absorption of cholesterol and the reabsorption of bile acids in the gut (Termannsen et al., 2022). The trials themselves show the result in people: LDL cholesterol falls most when a vegan diet replaces a usual diet, and much less when it replaces another healthy diet (Rees et al., 2021).

Why people eat less. Many vegan diets, especially low-fat ones, are high in fiber and water and low in energy density, meaning fewer calories in each bite. In 4 of 11 trials the vegan group ate measurably less energy than the comparison group (Termannsen et al., 2022), and in a tightly controlled inpatient study, people ate about 689 calories a day less on a low-fat plant-only diet than on an animal-based ketogenic diet when they could eat as much as they wanted (Hall et al., 2021). Eating less energy explains much of the weight change in the trials.

Why some minerals are harder to absorb. Plant foods contain iron only in its nonheme form, which the body absorbs less well than the heme iron in meat, so the recommended iron intake for vegetarians is 1.8 times higher (National Institutes of Health Office of Dietary Supplements, 2025a). Phytates in legumes and whole grains bind zinc and lower its absorption, and soaking beans, grains and seeds before cooking, or eating fermented foods, may improve absorption (National Institutes of Health Office of Dietary Supplements, 2026b). Plant foods are poor sources of iodine except for seaweed, so iodine intake depends on iodized salt or other sources (National Institutes of Health Office of Dietary Supplements, 2024; Raj et al., 2026).

Why bone deserves attention. Vegans eat less calcium on average than vegetarians or omnivores (Bickelmann et al., 2023), tend to have lower vitamin D levels (Raj et al., 2026), and often eat less protein and weigh less, all of which bear on bone (Tong et al., 2020). In the EPIC-Oxford fracture analysis, adjusting for calcium and protein intake weakened the higher fracture risk in vegans only slightly, so these factors do not fully explain it (Tong et al., 2020).

Proposed mechanisms

Several further explanations have been proposed for the effects of vegan diets on blood sugar, but have not been shown to account for them. Advocates of low-fat vegan diets propose that the diet reduces the fat stored inside muscle and liver cells, which is linked with insulin resistance (Barnard & Kahleova, 2023). The 2022 trial review mentions studies reporting a small increase in the energy the body uses to digest food (Termannsen et al., 2022). The Academy notes that healthful plant-based diets have been associated with a more diverse community of gut bacteria and proposes a role for the microbiome in metabolic and immune health (Raj et al., 2026). These are proposals. None of them supports a claim in section 4.

6. Risks, contraindications and myths

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Warnings from professional or regulatory bodies

No professional body opened for this page warns against a vegan diet for healthy adults. The warnings concern infants, children and pregnancy. The National Institutes of Health Office of Dietary Supplements states that "exclusively breastfed infants of women who consume no animal products might have very limited reserves of vitamin B12 and can develop vitamin B12 deficiency, sometimes very early in life," and that "undetected and untreated vitamin B12 deficiency in infants can result in neurological damage, failure to thrive, developmental delays, and anemia" (National Institutes of Health Office of Dietary Supplements, 2025c).

The European Society for Paediatric Gastroenterology, Hepatology and Nutrition states: "We recommend that infants, children and adolescents on a vegan diet should receive regular counselling from an appropriately qualified dietitian, be monitored by a paediatrician and have specific micronutrient supplements, including vitamin B12" (Verduci et al., 2025). A German pregnancy guideline reports that Switzerland and Austria still do not recommend a vegan diet during pregnancy (Alaze-Hagemann et al., 2026).

Nutrient gaps

Vitamin B12. Every source opened for this page agrees that a vegan diet cannot supply this nutrient without fortified foods or supplements. The recommended intake for adults is 2.4 micrograms a day, rising to 2.6 in pregnancy and 2.8 during breastfeeding (National Institutes of Health Office of Dietary Supplements, 2025c). The Academy states that the high prevalence of B12 deficiency among vegetarians, especially vegans, is well documented, and that supplements "may be the easiest and most reliable way" to ensure adequate status (Raj et al., 2026). A review of 18 studies that used sensitive markers found deficiency rates that were higher in vegans than in vegetarians and among those who had followed the diet since birth (Pawlak et al., 2013). Fortified nutritional yeast and fortified cereals supply B12; unfortified tempeh, beans and spinach supply little or none (National Institutes of Health Office of Dietary Supplements, 2025c).

Iodine. Seafood, eggs and dairy foods supply iodine, and the Office of Dietary Supplements notes that vegans, who eat none of them, "might not obtain sufficient amounts" and that plant milks contain relatively small amounts (National Institutes of Health Office of Dietary Supplements, 2024). Across the studies in a 2023 review, vegans commonly had lower iodine intakes than omnivores. One small UK sample reported 17.3 micrograms a day; results varied substantially between studies (Eveleigh et al., 2023). The recommended adult intake is 150 micrograms a day (National Institutes of Health Office of Dietary Supplements, 2024). Iodized salt, a supplement or seaweed can supply iodine, and the Academy advises education about kelp and other brown seaweeds, which can supply too much (Raj et al., 2026).

For pregnancy and breastfeeding, the American Academy of Pediatrics recommends a daily supplement with at least 150 micrograms of iodine for everyone, vegan or not, as reported by the Office of Dietary Supplements (National Institutes of Health Office of Dietary Supplements, 2024).

Calcium and vitamin D. Vegans eat substantially less calcium than vegetarians and omnivores (Bickelmann et al., 2023). The Office of Dietary Supplements notes that people who avoid dairy, including vegans, "typically need to eat foods fortified with calcium or take supplements" to reach recommended amounts, 1,000 milligrams a day for most adults (National Institutes of Health Office of Dietary Supplements, 2026a). The Academy suggests 2 to 3 servings a day of well-absorbed calcium sources, such as fortified soy and plant milks, calcium-set tofu, kale and fortified orange juice (Raj et al., 2026).

Vitamin D. Vitamin D deficiency is more common in people who follow a vegan diet (National Institutes of Health Office of Dietary Supplements, 2025d). Vitamin D3 in supplements is usually made from lanolin from sheep's wool, which matters to some vegans, while D2 is made from yeast. Animal-free D3 made from lichen is also available (National Institutes of Health Office of Dietary Supplements, 2025d).

Iron and zinc. Because plant iron is absorbed less well, the recommended iron intake for vegetarians is 1.8 times that for people who eat meat (National Institutes of Health Office of Dietary Supplements, 2025a). The Academy reports that vegetarian and vegan diets may be associated with lower ferritin, a blood measure of iron stores, although results were mixed and the certainty of the evidence very low, and that premenopausal vegetarian women have a high prevalence of iron deficiency (Raj et al., 2026). Vegans usually have lower zinc intakes and blood levels than people who eat animal foods (National Institutes of Health Office of Dietary Supplements, 2026b). Eating iron-rich plant foods with foods rich in vitamin C improves absorption (Raj et al., 2026).

Omega-3 fats. The long-chain omega-3 fats EPA and DHA are low or absent in unsupplemented vegan diets; the body converts only a small part of the plant omega-3 fat ALA into them, with reported rates under 15 percent (National Institutes of Health Office of Dietary Supplements, 2025b; Raj et al., 2026). The Academy advises regular ALA-rich foods such as walnuts and flax, chia and hemp seeds, and notes that algal oil supplements are an option but may not be required for health (Raj et al., 2026); the Office of Dietary Supplements advises pregnant vegans to ask a health care provider about them (National Institutes of Health Office of Dietary Supplements, 2025b).

Protein and choline. Protein is usually adequate in a varied diet that meets energy needs (Raj et al., 2026), but in a small Dutch study of long-term vegetarians and vegans with a median age of 76, the abstract reports that 5 of the 6 vegans ate less protein than recommended (Wildemast et al., 2026). Choline intake may be well below the adequate intake (Raj et al., 2026).

Who should not follow it without medical supervision

Pregnancy, breastfeeding and planning a pregnancy, because the current Academy position does not cover them, the data are limited, and an infant depends on the mother's B12 and iodine (Alaze-Hagemann et al., 2026; National Institutes of Health Office of Dietary Supplements, 2025c; Raj et al., 2026). Infants, children and adolescents, for whom a pediatric society recommends dietitian counseling, pediatric monitoring and supplements (Verduci et al., 2025). Older adults, because of protein needs and the risk of losing muscle (Domić et al., 2026; Raj et al., 2026). People with osteoporosis or a past fracture, given the fracture findings (Tong et al., 2020). People who absorb vitamin B12 poorly, such as those with pernicious anemia or after stomach or bowel surgery, and people taking metformin (National Institutes of Health Office of Dietary Supplements, 2025c).

People taking insulin, a sulfonylurea, blood pressure medication or warfarin, who keep the prescriber informed before a substantial change in eating; the reasons for diabetes medicines and warfarin follow below. People with kidney disease, whose needs depend on the stage of their disease, their laboratory results and whether they are on dialysis; so the kidney care team belongs in the plan. People with a history of disordered eating, for whom a diet with firm rules deserves the care team's involvement (Díaz-Goñi, Bizzozero-Peroni, et al., 2026).

Medication interactions

Insulin and sulfonylureas. Vegan diet trials in diabetes have reported participants needing less medication: 43 percent of the vegan group reduced diabetes medication over 22 weeks in one trial (Barnard et al., 2006), and total insulin dose fell by about 12 units a day in a 12-week trial in type 1 diabetes (Kahleova et al., 2025). Clinicians who use vegan diets write that people taking insulin or other diabetes medications need education on handling low blood sugar and regular contact with their care team so that medication can be reduced, because low blood sugar "can occur within days of a diet change" (Barnard & Kahleova, 2023). A coach never adjusts medication; the point of knowing this is to keep the prescriber in the loop.

Warfarin. Sudden changes in vitamin K intake can increase or decrease warfarin's effect, so people taking it need a consistent intake (National Institutes of Health Office of Dietary Supplements, 2021). A switch to a vegan diet rich in leafy greens is the kind of change the prescriber should hear about first. Metformin can reduce vitamin B12 absorption and lower blood B12 levels (National Institutes of Health Office of Dietary Supplements, 2025c), which adds to the B12 question for a vegan who takes it.

Signs it is going wrong

Physical signs a coach or family member might notice include tiredness, weakness, pale skin, a sore or smooth tongue, a racing heart, and numbness or tingling in the hands or feet, all of which can come from vitamin B12 deficiency among many other causes (National Institutes of Health Office of Dietary Supplements, 2025c); weight loss the person did not intend; loss of strength in an older adult; a fracture after a minor fall; and, in a child, growth that falls behind. Behavioral signs include a growing list of forbidden foods beyond animal products, anxiety about eating anywhere the person does not control, skipping meals, and withdrawing from eating with others. None of these is a diagnosis. Physical symptoms call for clinical assessment. Changes in eating behavior call for the assessment described under Referral red flags; the coach follows the referral procedure when that assessment raises a real concern.

Myths and where they came from

Myth: "Vegans can't get complete protein unless they combine foods at every meal."

Where it came from: individual plant proteins are lower in some essential amino acids, such as lysine and methionine. What is true: plant foods together contain all the essential amino acids, and a varied vegan diet that meets energy needs supplies them over the course of a day without combining at each meal (Raj et al., 2026). Older adults and athletes may need more protein than other adults (Raj et al., 2026).

Myth: "Seaweed, spirulina, tempeh or mushrooms give vegans their B12."

Where it came from: fermented foods and algae are often promoted as natural B12 sources. What is true: natural food sources of B12 are limited to animal foods, a half cup of tempeh supplies about 0.1 micrograms, and reliable vegan sources are fortified foods and supplements (National Institutes of Health Office of Dietary Supplements, 2025c; Raj et al., 2026).

Myth: "A vegan diet is proven to reverse heart disease and help you live longer."

Where it came from: promoters' claims and lower heart disease rates in some cohorts of vegetarians and vegans. What is true: vegan trials mainly measured risk factors, and the one small trial found that also monitored clinical events was too short to show prevention (Shah et al., 2018); for vegans specifically, the Academy rates the cohort evidence on cardiovascular disease as low certainty, with possibly no difference (Raj et al., 2026); and in the longer Adventist follow-up, deaths from any cause did not clearly differ between vegans and nonvegetarians (Abris et al., 2024).

Myth: "A well-planned vegan diet is proven to be right for every stage of life."

Where it came from: the Academy of Nutrition and Dietetics stated in 2016 that appropriately planned vegan diets are appropriate for all stages of the life cycle (Melina et al., 2016). What is true: the Academy's current position covers only adults who are not pregnant or breastfeeding (Raj et al., 2026), a 2025 pediatric position paper found the evidence on growth inconclusive (Verduci et al., 2025), and a German guideline reports no recommendation for or against a vegan diet in pregnancy (Alaze-Hagemann et al., 2026).

7. Key terms

Vegan diet

A diet with no foods of animal origin: no meat, poultry, fish, dairy, eggs or honey.

Veganism

A philosophy and way of living that seeks to avoid using animals for food, clothing or other purposes, as far as is possible and practicable; the diet is one part of it.

Plant-based

A loose term with no standard definition, used for diets that are mostly or completely free of animal foods.

Fortified food

A food with a nutrient added that it would not otherwise contain in useful amounts, such as plant milk with added calcium or cereal with added vitamin B12.

Vitamin B12

A vitamin needed for healthy blood cells and nerves that occurs naturally only in animal foods, so vegans get it from fortified foods or supplements.

Iodine

A mineral the thyroid gland needs, found mainly in seafood, dairy, eggs and iodized salt.

HbA1c

A blood test that reflects average blood sugar over the past 2 to 3 months, reported as a percentage. Interpreting a result belongs to a clinician.

LDL cholesterol

The cholesterol carried in low-density lipoprotein, which builds up in artery walls; diets high in saturated fat tend to raise it.

Randomized controlled trial

A study that assigns people to a diet or a comparison by chance, the strongest way to test whether the diet itself causes a result.

Cohort study

A study that follows people who already eat a certain way and records what happens to them. It can show that a pattern goes with an outcome but not, by itself, that it caused it.

Hazard ratio

A measure from studies that follow people over time: how much more or less often an event happens in one group than another. A hazard ratio of 0.85 means events happened about 15 percent less often.

Relative risk

How likely an outcome is in one group compared with another. A relative risk of 0.77 means about 23 percent lower.

Bone mineral density

A measure of how much mineral is packed into bone, used to judge bone strength and fracture risk.

Nonheme iron

The form of iron in plant foods, which the body absorbs less well than the heme iron in meat.

Alpha-linolenic acid (ALA)

The omega-3 fat found in plant foods such as walnuts and flaxseed. The body converts only a small part of it into the longer omega-3 fats EPA and DHA.

GRADE

The 4-level scale used in clinical guidelines to say how certain the evidence for a conclusion is: high, moderate, low or very low. It rates one outcome at a time, not the diet.

World Cancer Research Fund grading

A separate system for judging whether a food or diet causes or prevents cancer, with grades from "convincing" and "probable" down to "limited-suggestive" and "limited-no conclusion."

Orthorexia nervosa

A proposed term for an obsessive focus on eating only foods a person believes are healthy, to the point that it causes distress or harm.

8. Review questions

1. What does a vegan diet leave out that a vegetarian diet usually keeps, and why does a client who says "plant-based" need a follow-up question? Name 2 reasons people give for eating vegan besides health.
2. The vegan diet trials found a small fall in HbA1c and LDL cholesterol. In whom were they tested, for how long, against what, and how much support did participants get? What did the 2-year soul food trial add? (This question draws on section 4.)
3. A client who is 4 months pregnant tells you she has just gone vegan and feels great. What does the coach do, what does the coach not do, and where is the referral line?
4. A client says vegans live longer and that seaweed gives her all the vitamin B12 she needs. Where do those beliefs come from, and what do the sources on this page say? (This question draws on sections 4 and 6.)

9. References

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Abris, G. P., Shavlik, D. J., Mathew, R. O., Butler, F. M., Oh, J., Sirirat, R., Sveen, L. E., & Fraser, G. E. (2024). Cause-specific and all-cause mortalities in vegetarian compared with those in nonvegetarian participants from the Adventist Health Study-2 cohort. The American Journal of Clinical Nutrition, 120(4), 907-917. https://doi.org/10.1016/j.ajcnut.2024.07.028

Appleby, P. N., Crowe, F. L., Bradbury, K. E., Travis, R. C., & Key, T. J. (2016). Mortality in vegetarians and comparable nonvegetarians in the United Kingdom. The American Journal of Clinical Nutrition, 103(1), 218-230. https://doi.org/10.3945/ajcn.115.119461

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Aune, D., Schlesinger, S., & Sobiecki, J. G. (2026). Vegetarian and vegan diets and cancer incidence: A systematic review and meta-analysis of prospective studies. European Journal of Epidemiology, 41(5), 531-545. https://doi.org/10.1007/s10654-026-01380-8

Avnon, T., Paz Dubinsky, E., Lavie, I., Ben-Mayor Bashi, T., Anbar, R., & Yogev, Y. (2021). The impact of a vegan diet on pregnancy outcomes. Journal of Perinatology, 41(5), 1129-1133. https://doi.org/10.1038/s41372-020-00804-x

Ballarin, R. S., Lazzarin, T., Minicucci, M. F., Azevedo, P. S., Dos Santos Nunes Nogueira, V., Schoberer, D., Hoedl, M., & Eglseer, D. (2025). Vegetarian and vegan diets and the risk of hip fracture in adults: A systematic review and meta-analysis. Nutrition Reviews. Advance online publication. https://doi.org/10.1093/nutrit/nuaf241

Barnard, N. D., Alwarith, J., Rembert, E., Brandon, L., Nguyen, M., Goergen, A., Horne, T., do Nascimento, G. F., Lakkadi, K., Tura, A., Holubkov, R., & Kahleova, H. (2022). A Mediterranean diet and low-fat vegan diet to improve body weight and cardiometabolic risk factors: A randomized, cross-over trial. Journal of the American Nutrition Association, 41(2), 127-139. https://doi.org/10.1080/07315724.2020.1869625

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Barnard, N. D., Cohen, J., Jenkins, D. J. A., Turner-McGrievy, G., Gloede, L., Jaster, B., Seidl, K., Green, A. A., & Talpers, S. (2006). A low-fat vegan diet improves glycemic control and cardiovascular risk factors in a randomized clinical trial in individuals with type 2 diabetes. Diabetes Care, 29(8), 1777-1783. https://doi.org/10.2337/dc06-0606

Barnard, N. D., & Kahleova, H. (2023). Vegan diets for diabetes prevention and management of cardiometabolic risk. In M. A. Via & J. I. Mechanick (Eds.), Lifestyle medicine for prediabetes, type 2 diabetes, and cardiometabolic disease (pp. 207-225). CRC Press. https://doi.org/10.1201/9781003206637-10

Bickelmann, F. V., Leitzmann, M. F., Keller, M., Baurecht, H., & Jochem, C. (2023). Calcium intake in vegan and vegetarian diets: A systematic review and meta-analysis. Critical Reviews in Food Science and Nutrition, 63(31), 10659-10677. https://doi.org/10.1080/10408398.2022.2084027

Desmond, M. A., Sobiecki, J. G., Jaworski, M., Płudowski, P., Antoniewicz, J., Shirley, M. K., Eaton, S., Książyk, J., Cortina-Borja, M., De Stavola, B., Fewtrell, M., & Wells, J. C. K. (2021). Growth, body composition, and cardiovascular and nutritional risk of 5- to 10-y-old children consuming vegetarian, vegan, or omnivore diets. The American Journal of Clinical Nutrition, 113(6), 1565-1577. https://doi.org/10.1093/ajcn/nqaa445

Díaz-Goñi, V., Bizzozero-Peroni, B., Visier-Alfonso, M. E., Jiménez-López, E., Fernández-Rodríguez, R., López-Gil, J. F., Martins-de-Passos, T. O., González, A. D., Martínez-Vizcaíno, V., & Mesas, A. E. (2026). The associations between vegetarian and vegan diets and orthorexia nervosa symptoms in adults: A systematic review and meta-analysis. International Journal of Eating Disorders, 59(3), 409-423. https://doi.org/10.1002/eat.24596

Díaz-Goñi, V., Mesas, A. E., Jiménez-López, E., Olivo-Martins-de-Passos, T., Peral-Martínez, F., Peraile-Huerta, A. M., Visier-Alfonso, M. E., Garrido-Miguel, M., & Bizzozero-Peroni, B. (2026). Are vegetarian and vegan diets associated with eating disorder symptoms? A systematic review and meta-analysis. International Journal of Eating Disorders. Advance online publication. https://doi.org/10.1002/eat.70158

Dinu, M., Abbate, R., Gensini, G. F., Casini, A., & Sofi, F. (2017). Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies. Critical Reviews in Food Science and Nutrition, 57(17), 3640-3649. https://doi.org/10.1080/10408398.2016.1138447

Domić, J., Pinckaers, P. J. M., Grootswagers, P., Siebelink, E., Gerdessen, J. C., van Loon, L. J. C., & de Groot, L. C. P. G. M. (2025). A well-balanced vegan diet does not compromise daily mixed muscle protein synthesis rates when compared with an omnivorous diet in active older adults: A randomized controlled cross-over trial. The Journal of Nutrition, 155(4), 1141-1150. https://doi.org/10.1016/j.tjnut.2024.12.019

Domić, J., Grootswagers, P., Pinckaers, P. J. M., Melchers, M., van Loon, L. J. C., & de Groot, L. C. P. G. M. (2026). A self-selected vegan diet reduces skeletal muscle mass in healthy older adults: A randomized controlled trial. The American Journal of Clinical Nutrition, 124(3), Article 101416. https://doi.org/10.1016/j.ajcnut.2026.101416

Dunneram, Y., Lee, J. Y., Watling, C. Z., Lawson, I., Parsaeian, M., Fraser, G. E., Butler, F. M., Prabhakaran, D., Shridhar, K., Kondal, D., Mohan, V., Ali, M. K., Narayan, K. M. V., Tandon, N., Tong, T. Y. N., Travis, R. C., Chiu, T. H. T., Lin, M. N., Lin, C. L., . . . Perez-Cornago, A. (2026). Vegetarian diets and cancer risk: Pooled analysis of 1.8 million women and men in nine prospective studies on three continents. British Journal of Cancer, 134(8), 1218-1229. https://doi.org/10.1038/s41416-025-03327-4

Eveleigh, E. R., Coneyworth, L., & Welham, S. J. M. (2023). Systematic review and meta-analysis of iodine nutrition in modern vegan and vegetarian diets. British Journal of Nutrition, 130(9), 1580-1594. https://doi.org/10.1017/S000711452300051X

Guest, N. S., Raj, S., Landry, M. J., Mangels, A. R., Pawlak, R., Senkus, K. E., Handu, D., & Rozga, M. (2024). Vegetarian and vegan dietary patterns to treat adult type 2 diabetes: A systematic review and meta-analysis of randomized controlled trials. Advances in Nutrition, 15(10), Article 100294. https://doi.org/10.1016/j.advnut.2024.100294

Hall, K. D., Guo, J., Courville, A. B., Boring, J., Brychta, R., Chen, K. Y., Darcey, V., Forde, C. G., Gharib, A. M., Gallagher, I., Howard, R., Joseph, P. V., Milley, L., Ouwerkerk, R., Raisinger, K., Rozga, I., Schick, A., Stagliano, M., Torres, S., . . . Chung, S. T. (2021). Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake. Nature Medicine, 27(2), 344-353. https://doi.org/10.1038/s41591-020-01209-1

Jayaraman, A., McKay, B., Chiavaroli, L., Back, S., Fischer, I., Smith, R., Holubkov, R., Barnard, N. D., & Kahleova, H. (2026). Environmental footprint of a low-fat vegan diet and Mediterranean diet: A secondary analysis of a randomised clinical trial. BMJ Nutrition, Prevention & Health, 9(1), 247-251. https://doi.org/10.1136/bmjnph-2025-001482

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Kahleova, H., Maracine, C., Znayenko-Miller, T., Kuo, S., Herman, W. H., Holubkov, R., & Barnard, N. D. (2025). Can a vegan diet help people with type 1 diabetes save on insulin? A secondary analysis of a 12-week randomized clinical trial. BMC Nutrition, 11(1), Article 188. https://doi.org/10.1186/s40795-025-01175-2

Kahleova, H., Sutton, M., Maracine, C., Nichols, D., Monsivais, P., Holubkov, R., & Barnard, N. D. (2023). Vegan diet and food costs among adults with overweight: A secondary analysis of a randomized clinical trial. JAMA Network Open, 6(9), Article e2332106. https://doi.org/10.1001/jamanetworkopen.2023.32106

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Landry, M. J., Ward, C. P., Cunanan, K. M., Durand, L. R., Perelman, D., Robinson, J. L., Hennings, T., Koh, L., Dant, C., Zeitlin, A., Ebel, E. R., Sonnenburg, E. D., Sonnenburg, J. L., & Gardner, C. D. (2023). Cardiometabolic effects of omnivorous vs vegan diets in identical twins: A randomized clinical trial. JAMA Network Open, 6(11), Article e2344457. https://doi.org/10.1001/jamanetworkopen.2023.44457

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Lichtenstein, A. H., Khera, A., Anderson, C. A. M., Appel, L. J., DeSilva, D. M., Gardner, C., Hu, F. B., Jones, D. W., Petersen, K. S., & American Heart Association. (2026). 2026 dietary guidance to improve cardiovascular health: A scientific statement from the American Heart Association. Circulation, 153(18), e1285-e1295. https://doi.org/10.1161/CIR.0000000000001435

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Monteyne, A. J., Dunlop, M. V., Machin, D. J., Coelho, M. O. C., Pavis, G. F., Porter, C., Murton, A. J., Abdelrahman, D. R., Dirks, M. L., Stephens, F. B., & Wall, B. T. (2021). A mycoprotein-based high-protein vegan diet supports equivalent daily myofibrillar protein synthesis rates compared with an isonitrogenous omnivorous diet in older adults: A randomised controlled trial. British Journal of Nutrition, 126(5), 674-684. https://doi.org/10.1017/S0007114520004481

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Evidence rating and review record

Each row identifies the method, source, outcome or recommendation, and comparison being rated. Ratings from different tools are not interchangeable. The source is either a named published review or this page's own judgment. The rating in the banner is for this diet's main claimed outcome or recommendation, and the banner names the tool that produced it. A high rating means the research is solid; it does not mean the diet is right for everyone, and it does not mean a coach should recommend it.

Rows rated with GRADE use the same 4-level scale as the clinical guidelines you will meet in practice. High means further research is very unlikely to change the conclusion. Moderate means further research may change it. Low means further research is likely to change it. Very low means the conclusion is uncertain. GRADE rates each outcome separately, so a diet can be high for one outcome and very low for another.

One row uses the World Cancer Research Fund's criteria, which grade how strongly the evidence supports a causal link between a diet and cancer, from convincing and probable through limited-suggestive, meaning the evidence points in one direction but is too limited for a firm judgment, to limited-no conclusion and substantial effect on risk unlikely (Aune et al., 2026). These grades are not GRADE ratings and cannot be compared with them.

Three things about this table matter before reading it. The trial rows rate short-term changes in risk factors in adults with overweight or type 2 diabetes, mostly over 12 to 26 weeks, not the prevention of disease; the trials mainly measured risk factors, and none could show whether the diet prevents heart attacks, strokes or deaths. Rows marked as published are carried exactly as the review published them. And the row on vitamin B12 levels rates a comparison between vegans and nonvegetarians in observational studies; the need for a reliable B12 source rests on the established fact that B12 occurs naturally only in animal foods, not on that rating.

On a narrow screen, scroll the table sideways to see every column.

Evidence ratings, their sources and reasons

Outcome	Certainty	Who rated it, and for which comparison	Why it is rated this way
HbA1c (average blood sugar), 12 to 26 weeks (the banner)	Moderate	GRADE, published: Termannsen et al., 2022. Vegan diets against usual or other diets, in adults with overweight or type 2 diabetes; 9 randomized trials, 687 people	0.18 percentage points lower, from 0.07 to 0.29 lower. Randomized trials start high; the review lowered 1 level for imprecision. Risk of bias, inconsistency and publication bias were not lowered; the review did not assess indirectness. Reported exactly as published.
HbA1c in adults with type 2 diabetes	Moderate	GRADE, published: the Academy of Nutrition and Dietetics' evidence review (Guest et al., 2024; summarized in Raj et al., 2026). Vegan diets against therapeutic or nontherapeutic nonvegetarian diets in adults with type 2 diabetes; 12 to 74 weeks	The vegan trials together: 0.39 percentage points lower, from 0.18 to 0.60 lower. The review lowered certainty because of small sample sizes. Reported as published; the Academy's summary for vegan diets lists this outcome as a likely benefit with moderate certainty.
LDL cholesterol, 12 to 26 weeks	Low	GRADE, published: Termannsen et al., 2022. Same comparison as the banner; 8 trials, 684 people	0.24 mmol/L lower, from 0.07 to 0.40 lower, about 9 mg/dL. Lowered 1 level for imprecision and 1 for inconsistency between trials. Reported as published.
LDL cholesterol against no or minimal intervention, 16 to 26 weeks	Moderate	GRADE, published: Rees et al., 2021, Cochrane. Vegan diet against no or minimal intervention, in people at high risk of cardiovascular disease; 4 trials, 449 people	0.22 mmol/L lower, from 0.11 to 0.32 lower: probably a small reduction. Randomized trials start high; the review lowered 1 level for imprecision because of small sample size, and no other domain was lowered. Reported as published.
LDL cholesterol against another dietary intervention, 12 to 74 weeks	Moderate	GRADE, published: Rees et al., 2021, Cochrane. Vegan diet against another dietary intervention, in people at high risk of cardiovascular disease; 4 trials, 244 people	0.05 mmol/L lower, from 0.21 lower to 0.11 higher: probably little or no difference. The rating is for that estimate, not for an advantage. Lowered 1 level for imprecision because of small sample size; no other domain was lowered. Reported as published.
Systolic blood pressure, 12 to 26 weeks	Moderate	GRADE, published: Termannsen et al., 2022. Same comparison as the banner; 8 trials, 466 people	1.28 mm Hg higher, from 1.54 lower to 4.11 higher. No clear difference was detected. Lowered 1 level for imprecision. Reported as published.
Diastolic blood pressure, 12 to 26 weeks	Moderate	GRADE, published: Termannsen et al., 2022. Same comparison as the banner; 8 trials, 466 people	0.54 mm Hg higher, from 1.21 lower to 2.29 higher. No clear difference was detected. Lowered 1 level for imprecision. Reported as published.
Body weight, as measured, 12 to 26 weeks	Moderate	GRADE, published: Termannsen et al., 2022. Same comparison as the banner; 10 trials, 697 people	4.1 kg lower, from 2.4 to 5.9 kg lower. Lowered 1 level for inconsistency, because results varied widely between trials (I² 91 percent). Reported as a measurement, not as a goal.
Heart attack, stroke or death, in trials	Not rated	This page's own judgment, for long-term prevention of these events	Not rated by this page for long-term event prevention; short-term event surveillance does not provide a reliable estimate. One 8-week trial in 100 people with coronary artery disease monitored these outcomes and was not powered to compare them (Shah et al., 2018); none of the 13 trials in the Cochrane review, each at least 12 weeks, reported clinical event outcomes (Rees et al., 2021). The Academy separately lists cardiovascular events and mortality in adults with cardiovascular disease, against therapeutic nonvegetarian diets, as low certainty for "may be no difference" (Raj et al., 2026); that published label is not this page's rating.
Cardiovascular disease incidence, in the general population	Low, for "may be no difference"	GRADE, published: the Academy of Nutrition and Dietetics' evidence review, summarized in Raj et al., 2026. Vegan against nonvegetarian dietary patterns in generally healthy adults, from systematic reviews of observational studies	Reported as published. The umbrella review behind this summary used GRADE (Landry et al., 2024); the domain judgments for each outcome were not reported in the position paper. The conclusion for vegans is weaker than the Academy's conclusion for vegetarian diets including vegans, taken together.
Coronary heart disease incidence, in the general population	Low, for "may be no difference"	GRADE, published: Raj et al., 2026, from Landry et al., 2024. Same comparison as the row above	Reported as published. Not borrowed from the cardiovascular disease row; the Academy lists this outcome separately.
Stroke incidence, in the general population	Low, for "may be no difference"	GRADE, published: Raj et al., 2026, from Landry et al., 2024. Same comparison as the row above	Reported as published. Not borrowed from the cardiovascular disease row; the Academy lists this outcome separately.
Death from any cause, in cohorts	Low, for little or no difference	This page's own judgment, using GRADE. Vegans against nonvegetarians or regular meat eaters in adult prospective cohorts: Adventist Health Study 2, 1,008 vegan deaths (Abris et al., 2024); EPIC-Oxford with the Oxford Vegetarian Study, 166 vegan deaths (Appleby et al., 2016)	Hazard ratios 0.99, from 0.92 to 1.06, and 1.14, from 0.97 to 1.35. Cohort studies start low, and nothing lowered or raised the rating. Risk of bias: residual confounding and health-conscious comparison groups remain limitations. Adventist diet was measured at baseline; the British analysis updated diet groups during follow-up when information was available. No further deduction was made beyond the low observational starting point. Inconsistency: the intervals overlap, and results on different sides of 1 do not by themselves show inconsistency. Indirectness: adult cohorts that match the question. Imprecision: judged against this page's 10 percent threshold, selected after the results were known. The larger cohort's interval falls within 0.90 to 1.10; the smaller British estimate remains less precise. Publication bias: cannot be judged from 2 cohorts.
Total cancer incidence, in cohorts	Limited-suggestive	World Cancer Research Fund criteria, published: Aune et al., 2026. Vegans against nonvegetarians; 3 cohort studies reported in 2 publications, 141,115 participants	Relative risk 0.77, from 0.70 to 0.85; 0.82 after adjustment for body mass index. The grades for vegans are listed in the review's supplementary Table 25, which applies the criteria in its Table 23; the review gives no separate written justification for the vegan grades. This is not a GRADE rating. Breast cancer was also limited-suggestive; for colorectal and prostate cancer the grade was limited-no conclusion. A later pooled analysis of colorectal cancer was not part of this grading (Dunneram et al., 2026).
Fracture risk, in the general population	Low, as a potential harm	GRADE, published: the Academy of Nutrition and Dietetics' evidence review, summarized in Raj et al., 2026. Vegan against nonvegetarian dietary patterns in generally healthy adults	Reported as published. The Academy lists lower bone mineral density as a potential harm with very low certainty.
Hip fracture, in cohorts	Very low	GRADE, published: Ballarin et al., 2025. Vegans against meat eaters; 4 cohort studies, 5,344 vegans	Hazard ratio 1.75, from 1.17 to 2.63, with substantial inconsistency (I² 64 percent). Cohort studies start low; the review lowered the rating for serious risk of bias, inconsistency and imprecision. Reported as published.
Vitamin B12 blood levels, in the general population	Very low, as a potential harm	GRADE, published: the Academy of Nutrition and Dietetics' evidence review, summarized in Raj et al., 2026. Vegan against nonvegetarian dietary patterns	Reported as published. This rates an observational comparison of blood levels. It does not weaken the need for a B12 source, which follows from B12 occurring naturally only in animal foods (National Institutes of Health Office of Dietary Supplements, 2025c).

How this archive talks about weight. This page reports what studies measured, including body weight, and does not treat weight change as a goal or as a measure of a diet's success. Weight a person loses without meaning to can be a sign of a health problem, and where it is, the page names it as a reason to see a clinician. People are described the way the study described them.

Last reviewed: Reviewed and approved by James Peth, MS, MPH, PhD, on October 6, 2026, after a combined final review of the third batch of 5 archive pages, the plant-based family, the repairs it asked for, a focused recheck and a repair confirmation. Written October 4, 2026. Reviews first read as abstracts were read in full, so no rating is provisional, and no rating of this page's own rests on an abstract.

Updated October 21, 2026: The American Heart Association is now named as an author of its 2026 dietary guidance statement (Lichtenstein et al., 2026), as the publisher's citation credits it. No content changed.

Next scheduled review: August 2027. Pages built on annual guidance are rechecked each year. The federal fact sheets cited on this page are updated from time to time and should be rechecked first.

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Diet Reference Archive | One James

Prepared by James Peth, MS, MPH, PhD

© 2026–2027 One James. All rights reserved.

This page is for education and coaching practice. It is not medical or dietary advice.