Vegan diet
Meta-analyses of randomized trials find vegan diets lower weight about 2.5 to 4 kg and LDL cholesterol about 0.24 to 0.30 mmol/L, with a small HbA1c drop and no blood pressure change. Vegans had lower vitamin B12, iodine, calcium, vitamin D and zinc intake or status, and in a UK cohort more than twice the hip fractures of meat eaters.
- Status
- A dietary pattern, not a regulated product.
- Also called
- plant-based diet, whole-food plant-based, WFPB, strict vegetarian, total vegetarian, veganism
- Followed for
- weight loss, blood sugar, type 2 diabetes, cholesterol, blood pressure, heart health, cancer prevention, longevity
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Shown to help4
- StrongShown to lower weight about 2.5 to 4 kg against control diets in adults, most in adults with overweight or type 2 diabetes.
- StrongShown to lower LDL cholesterol about 0.24 to 0.30 mmol/L against omnivorous or control diets in adults.
- ModerateShown to lower HbA1c by about 0.18 points against control diets in adults with overweight or type 2 diabetes.
- LimitedLinked to about 15% lower total cancer incidence in a small number of cohort studies. Colorectal cancer did not differ significantly in one cohort.
Reported risks9
- StrongLinked to vitamin B12 deficiency rates higher in vegans than vegetarians, with typical vegan intake far below the 2.4 µg reference.Very common
- StrongLinked to the lowest iodine status of any diet group in vegans, below the WHO target range, most in countries without iodized salt programs.How often is not known
- StrongLinked to calcium intake below recommendations in most vegans studied, the lowest of any diet group.How often is not known
- StrongLinked to lower zinc intake and status in vegans, with a larger effect than in other vegetarians.How often is not known
- ModerateLinked to the lowest blood vitamin D in vegans in a UK cohort, about 56 against 77 nmol/L in meat eaters.How often is not known
- ModerateLinked to about 2.3 times the hip fractures and 43% more total fractures in vegans than meat eaters in a UK cohort, and to lower bone density.How often is not known
- LimitedMixed results: one review found lower iron status on plant-based diets, while a review of vegan diets found no link to iron deficiency.How often is not known
- LimitedLimited evidence: blood EPA and DHA were lower in vegan men than meat eaters and did not change with years on the diet.How often is not known
- LimitedLimited evidence: one review found low selenium intake in European vegans.How often is not known
What people follow it for, and what was found
Shown to help4
Weight
Shown to lower weight about 2.5 to 4 kg against control diets in adults, most in adults with overweight or type 2 diabetes.
Compared with the participants' habitual diet, unchanged, in 3 trials in US and New Zealand adults, and in 8 trials a National Cholesterol Education Program diet, American Diabetes Association and Korean Diabetes Association diets, a portion-controlled diet, a Mediterranean diet, a low-fat diet, a healthy omnivorous diet or a high-carbohydrate lacto-ovo vegetarian diet [1]; non-vegetarian diets [2]
The numbers and sources
- Effect
- In 11 trials of 12 weeks or more (796 participants), vegan diets lowered weight by 4.1 kg against control diets (95% CI -5.9 to -2.4) and BMI by 1.38 [1]. In a meta-analysis of 12 RCTs, the vegan subgroup lost 2.52 kg more than non-vegetarian diets (95% CI -3.02 to -1.98) [2].
- Population
- Adults with overweight or type 2 diabetes [1]; adults in RCTs, median 18 weeks [2].
- Sources
- [1], [2]
- Caveats
- Part of the effect may reflect lower energy intake and different macronutrients on the vegan diets [1]. Weight loss in vegetarian trials shrank at a year or more [2].
LDL cholesterol
Shown to lower LDL cholesterol about 0.24 to 0.30 mmol/L against omnivorous or control diets in adults.
Compared with the participants' habitual diet, unchanged, in 3 trials in US and New Zealand adults, and in 8 trials a National Cholesterol Education Program diet, American Diabetes Association and Korean Diabetes Association diets, a portion-controlled diet, a Mediterranean diet, a low-fat diet, a healthy omnivorous diet or a high-carbohydrate lacto-ovo vegetarian diet [1]; an omnivorous diet [3]
The numbers and sources
- Effect
- Vegan diets lowered total cholesterol by 0.30 mmol/L and LDL by 0.24 mmol/L (95% CI -0.40 to -0.07), with no change in HDL or triglycerides [1]. In 30 RCTs of vegetarian or vegan diets, LDL fell 0.30 mmol/L (95% CI -0.40 to -0.19) and apolipoprotein B 12.92 mg/dL, with similar effects across intervention diet types [3].
- Population
- Adults with overweight or type 2 diabetes [1]; adults in 30 RCTs [3].
- Sources
- [1], [3]
- Caveats
- The larger review pooled vegan and vegetarian diets [3].
Blood sugar
Shown to lower HbA1c by about 0.18 points against control diets in adults with overweight or type 2 diabetes.
Compared with the participants' habitual diet, unchanged, in 3 trials in US and New Zealand adults, and in 8 trials a National Cholesterol Education Program diet, American Diabetes Association and Korean Diabetes Association diets, a portion-controlled diet, a Mediterranean diet, a low-fat diet, a healthy omnivorous diet or a high-carbohydrate lacto-ovo vegetarian diet [1]
The numbers and sources
Cancer
Linked to about 15% lower total cancer incidence in a small number of cohort studies. Colorectal cancer did not differ significantly in one cohort.
Compared with omnivores, in cohort studies [5]; nonvegetarians in the same Seventh-day Adventist cohort in North America [6]
The numbers and sources
- Effect
- In cohort studies, vegan diets were linked to lower total cancer incidence (RR 0.85, 95% CI 0.75 to 0.95) [5]. In the Adventist cohort, colorectal cancer in vegans did not differ significantly from nonvegetarians (HR 0.84, 95% CI 0.59 to 1.19) [6].
- Population
- Adults in prospective cohorts [5]; 77,659 Seventh-day Adventists followed a mean 7.3 years [6]. Observational.
- Sources
- [5], [6]
- Caveats
- Observational. The review notes the vegan result came from a limited number of studies [5].
Not shown to help1
Blood pressure
Not shown to lower blood pressure in trials of adults with overweight or type 2 diabetes. One cohort linked vegan diets to less hypertension.
Compared with the participants' habitual diet, unchanged, in 3 trials in US and New Zealand adults, and in 8 trials a National Cholesterol Education Program diet, American Diabetes Association and Korean Diabetes Association diets, a portion-controlled diet, a Mediterranean diet, a low-fat diet, a healthy omnivorous diet or a high-carbohydrate lacto-ovo vegetarian diet [1]; omnivorous Adventists in the same cohort, white adults in the USA and Canada [4]
The numbers and sources
- Effect
- Blood pressure did not change in 11 trials [1]. In an Adventist cohort sample, vegans had lower systolic (by 6.8 mmHg) and diastolic (by 6.9 mmHg) blood pressure than omnivores, and lower odds of hypertension (OR 0.37, 95% CI 0.19 to 0.74) [4].
- Population
- Adults with overweight or type 2 diabetes [1]; 500 white Adventists, observational [4].
- Sources
- [1], [4]
- Caveats
- The cohort link was partly explained by lower body weight [4].
How trials defined it
Vegan diets exclude animals and all their by-products [7]. Cardiometabolic trials ran 12 weeks or more against control diets [1], and vegetarian weight trials ran a median 18 weeks with a vegan subgroup [2].
Risks
Reported risks8
Vitamin B12 deficiency
Linked to vitamin B12 deficiency rates higher in vegans than vegetarians, with typical vegan intake far below the 2.4 µg reference.
The numbers and sources
- How common
- Very common: more than 1 in 10 people.
- Effect
- In 18 studies measuring methylmalonic acid or holotranscobalamin, deficiency rates in vegetarians ranged from 11 to 90% by age group, and were higher in vegans than in vegetarians [8]. In European studies, vegan B12 intake was 0.24 to 0.49 µg a day against a 2.4 µg recommendation [7]. A review of 141 studies found vegans had the lowest B12 intake [9].
- Population
- Vegetarians and vegans of all ages [8]; vegans in 48 European studies [7]; adults in 141 studies [9]. Observational.
- Sources
- [7], [8], [9]
- Caveats
- The deficiency review gives combined ranges, not separate vegan rates [8].
Low iodine
Linked to the lowest iodine status of any diet group in vegans, below the WHO target range, most in countries without iodized salt programs.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- In 15 studies (127,094 adults), vegans had the lowest median urinary iodine and did not reach the target status [10]. In 11 studies (4,421 adults), vegans had the lowest median urinary iodine (12.2 µg/L) and intake (17.3 µg a day), against a WHO target range of 100 to 200 µg/L [11]. A review of 141 studies found vegans had the lowest iodine intake and lower iodine status [9].
- Population
- Adults in industrialized countries [10]; adults in 11 studies [11]; adults in 141 studies [9]. Observational.
- Sources
- [9], [10], [11]
- Caveats
- Some vegans had very high intakes from seaweed [10]. Two of the reviews come from the same research group [10][11].
Low calcium intake
Linked to calcium intake below recommendations in most vegans studied, the lowest of any diet group.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- Calcium intake in most vegans was below the 750 mg a day recommendation [7]. A review of 141 studies found vegans had the lowest calcium intake [9].
- Population
- Vegans in 48 European studies [7]; adults in 141 studies [9]. Observational.
- Sources
- [7], [9]
- Caveats
- Intake, not a blood measure. Calcium intake partly explained the vegan fracture finding in one cohort [12].
Lower vitamin D
Linked to the lowest blood vitamin D in vegans in a UK cohort, about 56 against 77 nmol/L in meat eaters.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- Vegans had the lowest vitamin D intake (0.7 µg a day) and plasma 25-hydroxyvitamin D (55.8 nmol/L) against meat eaters (3.1 µg a day and 77.0 nmol/L). The gap was 38% in winter and 20% in summer [13]. Reviews found vitamin D intake and status lower on plant-based diets and vitamin D intake low in vegans [7][9].
- Population
- 2,107 white UK adults including 89 vegans [13]; vegans in European studies [7]; adults in 141 studies [9]. Observational.
- Sources
- [7], [9], [13]
- Caveats
- Cross-sectional, with few vegans in the blood study [13]. Meat eaters also had low vitamin D intake in [9].
Lower zinc status
Linked to lower zinc intake and status in vegans, with a larger effect than in other vegetarians.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- Across 26 studies comparing people on vegetarian diets with non-vegetarians, zinc intake was 0.88 mg a day lower and serum zinc 0.93 µmol/L lower on vegetarian diets, with a larger difference in vegans [14]. European studies found low zinc intake in vegans [7], and a review of 141 studies found zinc intake and status lower on plant-based diets [9].
- Population
- Habitual vegetarians and vegans [14]; vegans in European studies [7]; adults in 141 studies [9]. Observational.
- Sources
- [7], [9], [14]
- Caveats
- The zinc meta-analysis reports the vegan difference without a separate figure [14].
Lower omega-3 (EPA and DHA)
Limited evidence: blood EPA and DHA were lower in vegan men than meat eaters and did not change with years on the diet.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- Plasma EPA and DHA proportions were lower in vegans and vegetarians than meat eaters and were not linked to how long people had followed the diet [15]. A review found EPA and DHA intake lower in vegans and vegetarians [9].
- Population
- 232 vegan, 231 vegetarian and 196 meat-eating UK men [15]; adults in 141 studies [9]. Observational.
- Sources
- [9], [15]
- Caveats
- One status study, in men only, with no effect sizes in the abstract [15].
Low selenium intake
Limited evidence: one review found low selenium intake in European vegans.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- A review of 48 European studies found vegan diets associated with low selenium intake and listed selenium among possible deficiencies [7].
- Population
- Vegans in 12 cohorts and 36 cross-sectional studies [7]. Observational.
- Sources
- [7]
- Caveats
- Intake only, with no blood measures reported in the abstract [7].
Fractures and bone density
Linked to about 2.3 times the hip fractures and 43% more total fractures in vegans than meat eaters in a UK cohort, and to lower bone density.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- In EPIC-Oxford over 17.6 years, vegans had more hip fractures (HR 2.31, 95% CI 1.66 to 3.22), about 14.9 more per 1,000 people over 10 years, and more total (HR 1.43), leg (HR 2.05) and other main site fractures than meat eaters [16]. An earlier analysis found 30% more fractures in vegans (rate ratio 1.30, 95% CI 1.02 to 1.66), which fell to 1.15 (95% CI 0.89 to 1.49) after adjusting for energy and calcium intake, and to 1.00 in people eating at least 525 mg of calcium a day [12]. Across 20 studies, vegans had lower bone mineral density at the femoral neck and lumbar spine and higher fracture rates than omnivores [17].
- Population
- 54,898 UK adults including 1,982 vegans [16]; 34,696 UK adults including 1,126 vegans [12]; 37,134 people in 20 studies [17]. Observational.
- Sources
- [12], [16], [17]
- Caveats
- Observational. In the later analysis, the links remained after adjusting for calcium and protein intake [16], while in the earlier analysis they did not [12]. Wrist and ankle fractures did not differ [16].
Mixed results1
Iron status
Mixed results: one review found lower iron status on plant-based diets, while a review of vegan diets found no link to iron deficiency.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- A review of 141 studies found iron intake and status generally lower on plant-based diets than in meat eaters [9]. A review of 48 European studies found vegan diets were not related to iron deficiency [7].
- Population
- Adults in 141 studies [9]; vegans in 48 European studies [7]. Observational.
- Sources
- [7], [9]
- Caveats
- The reviews used different measures, intake against recommendations in [7] and intake plus biomarkers in [9].
Supplements to consider
The nutrients research linked to this diet running short, each with its own page.
Vitamin B12
Strong Linked to vitamin B12 deficiency rates higher in vegans than vegetarians, with typical vegan intake far below the 2.4 µg reference.
Iodine
Strong Linked to the lowest iodine status of any diet group in vegans, below the WHO target range, most in countries without iodized salt programs.
Calcium
Strong Linked to calcium intake below recommendations in most vegans studied, the lowest of any diet group.
Vitamin D
Moderate Linked to the lowest blood vitamin D in vegans in a UK cohort, about 56 against 77 nmol/L in meat eaters.
Zinc
Strong Linked to lower zinc intake and status in vegans, with a larger effect than in other vegetarians.
Iron
Limited Mixed results: one review found lower iron status on plant-based diets, while a review of vegan diets found no link to iron deficiency.
Fish oil
Limited Limited evidence: blood EPA and DHA were lower in vegan men than meat eaters and did not change with years on the diet.
Selenium
Limited Limited evidence: one review found low selenium intake in European vegans.
Sources
- Termannsen A, Clemmensen KKB, Thomsen JM, et al. Effects of vegan diets on cardiometabolic health: A systematic review and meta-analysis of randomized controlled trials. Obesity Reviews. 2022. https://doi.org/10.1111/obr.13462
- Huang RY, Huang CC, Hu FB, et al. Vegetarian Diets and Weight Reduction: a Meta-Analysis of Randomized Controlled Trials. Journal of General Internal Medicine. 2016. https://doi.org/10.1007/s11606-015-3390-7
- Koch CA, Kjeldsen EW, Frikke-Schmidt R. Vegetarian or vegan diets and blood lipids: a meta-analysis of randomized trials. European Heart Journal. 2023. https://doi.org/10.1093/eurheartj/ehad211
- Pettersen BJ, Anousheh R, Fan J, et al. Vegetarian diets and blood pressure among white subjects: results from the Adventist Health Study-2 (AHS-2). Public Health Nutrition. 2012. https://doi.org/10.1017/S1368980011003454
- Dinu M, Abbate R, Gensini GF, et al. Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies. Critical Reviews in Food Science and Nutrition. 2017. https://doi.org/10.1080/10408398.2016.1138447
- Orlich MJ, Singh PN, Sabaté J, et al. Vegetarian dietary patterns and the risk of colorectal cancers. JAMA Internal Medicine. 2015. https://doi.org/10.1001/jamainternmed.2015.59
- Bakaloudi DR, Halloran A, Rippin HL, et al. Intake and adequacy of the vegan diet. A systematic review of the evidence. Clinical Nutrition. 2021. https://doi.org/10.1016/j.clnu.2020.11.035
- Pawlak R, Parrott SJ, Raj S, et al. How prevalent is vitamin B12 deficiency among vegetarians? Nutrition Reviews. 2013. https://doi.org/10.1111/nure.12001
- Neufingerl N, Eilander A. Nutrient Intake and Status in Adults Consuming Plant-Based Diets Compared to Meat-Eaters: A Systematic Review. Nutrients. 2021. https://doi.org/10.3390/nu14010029
- Eveleigh ER, Coneyworth LJ, Avery A, et al. Vegans, Vegetarians, and Omnivores: How Does Dietary Choice Influence Iodine Intake? A Systematic Review. Nutrients. 2020. https://doi.org/10.3390/nu12061606
- Eveleigh ER, Coneyworth L, Welham SJM. Systematic review and meta-analysis of iodine nutrition in modern vegan and vegetarian diets. British Journal of Nutrition. 2023. https://doi.org/10.1017/S000711452300051X
- Appleby P, Roddam A, Allen N, et al. Comparative fracture risk in vegetarians and nonvegetarians in EPIC-Oxford. European Journal of Clinical Nutrition. 2007. https://doi.org/10.1038/sj.ejcn.1602659
- Crowe FL, Steur M, Allen NE, et al. Plasma concentrations of 25-hydroxyvitamin D in meat eaters, fish eaters, vegetarians and vegans: results from the EPIC-Oxford study. Public Health Nutrition. 2011. https://doi.org/10.1017/S1368980010002454
- Foster M, Chu A, Petocz P, et al. Effect of vegetarian diets on zinc status: a systematic review and meta-analysis of studies in humans. Journal of the Science of Food and Agriculture. 2013. https://doi.org/10.1002/jsfa.6179
- Rosell MS, Lloyd-Wright Z, Appleby PN, et al. Long-chain n-3 polyunsaturated fatty acids in plasma in British meat-eating, vegetarian, and vegan men. The American Journal of Clinical Nutrition. 2005. https://doi.org/10.1093/ajcn/82.2.327
- Tong TYN, Appleby PN, Armstrong MEG, et al. Vegetarian and vegan diets and risks of total and site-specific fractures: results from the prospective EPIC-Oxford study. BMC Medicine. 2020. https://doi.org/10.1186/s12916-020-01815-3
- Iguacel I, Miguel-Berges ML, Gómez-Bruton A, et al. Veganism, vegetarianism, bone mineral density, and fracture risk: a systematic review and meta-analysis. Nutrition Reviews. 2019. https://doi.org/10.1093/nutrit/nuy045