Hostname: page-component-8448b6f56d-dnltx Total loading time: 0 Render date: 2024-04-19T11:49:58.429Z Has data issue: false hasContentIssue false

Health effects of vegetarian and vegan diets

Published online by Cambridge University Press:  07 March 2007

Timothy J. Key*
Cancer Research UK Epidemiology Unit, University of Oxford, Richard Doll Building, Roosevelt Drive, Oxford OX3 7LF, UK
Paul N. Appleby
Cancer Research UK Epidemiology Unit, University of Oxford, Richard Doll Building, Roosevelt Drive, Oxford OX3 7LF, UK
Magdalena S. Rosell
Cancer Research UK Epidemiology Unit, University of Oxford, Richard Doll Building, Roosevelt Drive, Oxford OX3 7LF, UK
*Corresponding author: Professor Tim Key, fax +44 1865 289 610, email
Rights & Permissions [Opens in a new window]


Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Vegetarian diets do not contain meat, poultry or fish; vegan diets further exclude dairy products and eggs. Vegetarian and vegan diets can vary widely, but the empirical evidence largely relates to the nutritional content and health effects of the average diet of well-educated vegetarians living in Western countries, together with some information on vegetarians in non-Western countries. In general, vegetarian diets provide relatively large amounts of cereals, pulses, nuts, fruits and vegetables. In terms of nutrients, vegetarian diets are usually rich in carbohydrates, n−6 fatty acids, dietary fibre, carotenoids, folic acid, vitamin C, vitamin E and Mg, and relatively low in protein, saturated fat, long-chain n−3 fatty acids, retinol, vitamin B12 and Zn; vegans may have particularly low intakes of vitamin B12 and low intakes of Ca. Cross-sectional studies of vegetarians and vegans have shown that on average they have a relatively low BMI and a low plasma cholesterol concentration; recent studies have also shown higher plasma homocysteine concentrations than in non-vegetarians. Cohort studies of vegetarians have shown a moderate reduction in mortality from IHD but little difference in other major causes of death or all-cause mortality in comparison with health-conscious non-vegetarians from the same population. Studies of cancer have not shown clear differences in cancer rates between vegetarians and non-vegetarians. More data are needed, particularly on the health of vegans and on the possible impacts on health of low intakes of long-chain n−3 fatty acids and vitamin B12. Overall, the data suggest that the health of Western vegetarians is good and similar to that of comparable non-vegetarians.

Symposium on ‘Plant foods and public health’
Copyright © The Nutrition Society 2006


Allen, NE, Appleby, PN, Davey, GK, Kaaks, R, Rinaldi, S & Key, TJ (2002) The associations of diet with serum insulin-like growth factor I and its main binding proteins in 292 women meat-eaters, vegetarians, and vegans. Cancer Epidemiology, Biomarkers & Prevention 11 14411448.Google ScholarPubMed
Allen, NE, Appleby, PN, Davey, GK & Key, TJ (2000) Hormones and diet: low insulin-like growth factor-I but normal bioavailable androgens in vegan men. British Journal of Cancer 83 9597.CrossRefGoogle ScholarPubMed
American Dietetic Association and Dietitians of Canada (2003) Position of the American Dietetic Association and Dietitians of Canada: Vegetarian diets. Journal of the American Dietetic Association 103 748765.CrossRefGoogle Scholar
Antony, AC (2003) Vegetarianism and vitamin B-12 (cobalamin) deficiency. American Journal of Clinical Nutrition 78 36.CrossRefGoogle ScholarPubMed
Appleby, PN, Davey, GK, Key, TJ (2002) Hypertension and blood pressure among meat eaters, fish eaters, vegetarians and vegans in EPIC-Oxford. Public Health Nutrition 5 645654.CrossRefGoogle ScholarPubMed
Armstrong, BK, Davis, RE, Nicol, DJ, van Merwyk, AJ, Larnwood, CJ (1974) Hematological, vitamin B-12 and folate studies on seventh-day Adventist vegetarians. American Journal of Clinical Nutrition 27 712718.CrossRefGoogle ScholarPubMed
Barr, SI & Rideout, CA (2004) Nutritional considerations for vegetarian athletes. Nutrition 20 696703.CrossRefGoogle ScholarPubMed
Beilin, LJ, Rouse, IL, Armstrong, BK, Margetts, BM & Vandongen, R (1988) Vegetarian diet and blood pressure levels: incidental or causal association? American Journal of Clinical Nutrition 48 806810.CrossRefGoogle ScholarPubMed
Chang-Claude, J, Hermann, S, Eilber, U & Steindorf, K (2005) Lifestyle determinants and mortality in German vegetarians and health-conscious persons: results of a 21-year follow-up. Cancer Epidemiology, Biomarkers & Prevention 14 963968.CrossRefGoogle ScholarPubMed
Dagnelie, PC (1997) Some algae are potentially adequate sources of vitamin B-12 for vegans. Journal of Nutrition 127 379CrossRefGoogle ScholarPubMed
Dagnelie, PC, van Staveren, WA, van den Berg, H (1991) Vitamin B-12 from algae appears not to be bioavailable. American Journal of Clinical Nutrition 53 695697.CrossRefGoogle Scholar
Davey, GK, Spencer, EA, Appleby, PN, Allen, NE, Knox, KH & Key, TJ (2003) EPIC-Oxford: lifestyle characteristics and nutrient intakes in a cohort of 33 883 meat-eaters and 31 546 non meat-eaters in the UK. Public Health Nutrition 6 259269.CrossRefGoogle Scholar
Davis, BC, Kris-Etherton, PM (2003) Achieving optimal essential fatty acid status in vegetarians: current knowledge and practical implications. American Journal of Clinical Nutrition 78 Suppl. 640S646SCrossRefGoogle ScholarPubMed
Department of Health (1991) Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. Report on Health and Social Subjects no. 41. London: H. M. Stationery Office.Google Scholar
Dos Santos Silva, I, Mangtani, P, McCormack, V, Bhakta, D, Sevak, L & McMichael, AJ (2002) Lifelong vegetarianism and risk of breast cancer: a population-based case-control study among South Asian migrant women living in England. International Journal of Cancer 99 238244.CrossRefGoogle ScholarPubMed
Eaton, NE, Reeves, GK, Appleby, PN & Key, TJ (1999) Endogenous sex hormones and prostate cancer: a quantitative review of prospective studies. British Journal of Cancer 80 930934.CrossRefGoogle ScholarPubMed
Fraser, GE (1999) Associations between diet and cancer, ischemic heart disease, and all-cause mortality in non-Hispanic white California Seventh-day Adventists. American Journal of Clinical Nutrition 70, Suppl. 532S538S.CrossRefGoogle ScholarPubMed
Henderson, L, Gregory, J & Swan, G (2002) National Diet and Nutrition Survey: Adults Aged 19 to 64 Years. vol. 1: Types and Quantities of Foods Consumed. London: The Stationery Office.Google Scholar
Herbert, V (1988) Vitamin B-12: plant sources, requirements, and assay. American Journal of Clinical Nutrition 48 Suppl. 852858CrossRefGoogle ScholarPubMed
Herrmann, W & Geisel, J (2002) Vegetarian lifestyle and monitoring of vitamin B-12 status. Clinica Chimica Acta 326 4759.CrossRefGoogle ScholarPubMed
Herrmann, W, Schorr, H, Obeid, R & Geisel, J (2003) Vitamin B-12 status, particularly holotranscobalamin II and methylmalonic acid concentrations, and hyperhomocysteinemia in vegetarians. American Journal of Clinical Nutrition 78 131136.CrossRefGoogle ScholarPubMed
Hung, CJ, Huang, PC, Lu, SC, Li, YH, Huang, HB, Lin, BF, Chang, SJ & Chou, HF (2002) Plasma homocysteine levels in Taiwanese vegetarians are higher than those of omnivores. Journal of Nutrition 132 152158.CrossRefGoogle ScholarPubMed
International Vegetarian Union (2005) 37th IVU World Vegetarian Congress Goa, India, September 10–16, 2006. Healthy Lifestyle – Vegetarian Way! (accessed June 2005).Google Scholar
Jebb, SA, Rennie, KL, Cole, TJ (2004) Prevalence of overweight and obesity among young people in Great Britain. Public Health Nutrition 7 461465.CrossRefGoogle ScholarPubMed
Jenkins, DJ, Kendall, CW, Marchie, A, Faulkner, DA, Wong, JM, de Souza, R et al. (2003) Effects of a dietary portfolio of cholesterol-lowering foods vs lovastatin on serum lipids and C-reactive protein. Journal of the American Medical Association 290 502510.CrossRefGoogle ScholarPubMed
Key, T, Appleby, P, Barnes, I & Reeves, G (2002) Endogenous sex hormones and breast cancer in postmenopausal women: reanalysis of nine prospective studies. Journal of the National Cancer Institute 94 606616.Google ScholarPubMed
Key, T & Davey, G (1996) Prevalence of obesity is low in people who do not eat meat. British Medical Journal 313 816817.CrossRefGoogle Scholar
Key, TJ, Appleby, PN, Davey, GK, Allen, NE, Spencer, EA & Travis, RC (2003) Mortality in British vegetarians: review and preliminary results from EPIC-Oxford. American Journal of Clinical Nutrition 78, Suppl. 533S538SCrossRefGoogle ScholarPubMed
Key, TJ, Davey, GK & Appleby, PN (1999 a) Health benefits of a vegetarian diet. Proceedings of the Nutrition Society 58 271275.CrossRefGoogle ScholarPubMed
Key, TJ, Fraser, GE, Thorogood, M, Appleby, PN, Beral, V, Reeves, G et al. (1999 b) Mortality in vegetarians and nonvegetarians: detailed findings from a collaborative analysis of 5 prospective studies. American Journal of Clinical Nutrition 70, Suppl. 516S524S.CrossRefGoogle ScholarPubMed
Key, TJ, Schatzkin, A, Willett, WC, Allen, NE, Spencer, EA, Travis, RC (2004) Diet, nutrition and the prevention of cancer. Public Health Nutrition 7 187200.CrossRefGoogle ScholarPubMed
Koebnick, C, Hoffmann, I, Dagnelie, PC, Heins, UA, Wickramasinghe, SN, Ratnayaka, ID, Gruendel, S, Lindemans, J & Leitzmann, C (2004) Long-term ovo-lacto vegetarian diet impairs vitamin B-12 status in pregnant women. Journal of Nutrition 134 33193326.CrossRefGoogle ScholarPubMed
Kwok, T, Cheng, G, Woo, J, Lai, WK, Pang, CP (2002) Independent effect of vitamin B12 deficiency on hematological status in older Chinese vegetarian women. American Journal of Hematology 70 186190.CrossRefGoogle ScholarPubMed
Law, MR, Wald, NJ, Wu, T, Hackshaw, A & Bailey, A (1994) Systematic underestimation of association between serum cholesterol concentration and ischaemic heart disease in observational studies: data from the BUPA study. British Medical Journal 308 363366.CrossRefGoogle ScholarPubMed
Mann, NJ, Li, D, Sinclair, AJ, Dudman, NP, Guo, XW, Elsworth, GR, Wilson, AK, Kelly, FD (1999) The effect of diet on plasma homocysteine concentrations in healthy male subjects. European Journal of Clinical Nutrition 53 895899.CrossRefGoogle ScholarPubMed
Mezzano, D, Kosiel, K, Martinez, C, Cuevas, A, Panes, O, Aranda, E, Strobel, P, Perez, DD, Pereira, J, Rozowski, J & Leighton, F (2000) Cardiovascular risk factors in vegetarians. Normalization of hyperhomocysteinemia with vitamin B(12) and reduction of platelet aggregation with n-3 fatty acids. Thrombosis Research 100 153160.CrossRefGoogle ScholarPubMed
Mills, PK, Beeson, WL, Phillips, RL & Fraser, GE (1989 a) Dietary habits and breast cancer incidence among Seventh-day Adventists. Cancer 64 582590.3.0.CO;2-V>CrossRefGoogle ScholarPubMed
Mills, PK, Beeson, WL, Phillips, RL & Fraser, GE (1989 b) Cohort study of diet, lifestyle, and prostate cancer in Adventist men. Cancer 64 598604.3.0.CO;2-6>CrossRefGoogle ScholarPubMed
New, SA (2004) Do vegetarians have a normal bone mass? Osteoporosis International 15 679688.CrossRefGoogle ScholarPubMed
Nieman, DC (1999) Physical fitness and vegetarian diets: is there a relation? American Journal of Clinical Nutrition 70, Suppl. 570S575S.CrossRefGoogle ScholarPubMed
Norat, T, Bingham, S, Ferrari, P, Slimani, N, Jenab, M, Mazuir, M et al. (2005) Meat, fish, and colorectal cancer risk: the European Prospective Investigation into Cancer and Nutrition. Journal of the National Cancer Institute 97 906916.CrossRefGoogle ScholarPubMed
Pais, P, Pogue, J, Gerstein, H, Zachariah, E, Savitha, D, Jayprakash, S, Nayak, PR & Yusuf, S (1996) Risk factors for acute myocardial infarction in Indians: a case-control study. Lancet 348 358363.CrossRefGoogle ScholarPubMed
Peeters, PH, Keinan-Boker, L, van der Schouw, YT, Grobbee, DB (2003) Phytoestrogens and breast cancer risk. Review of the epidemiological evidence. Breast Cancer Research and Treatment 77 171183.CrossRefGoogle ScholarPubMed
Rao, DN, Ganesh, B & Desai, PB (1994) Role of reproductive factors in breast cancer in a low-risk area: a case-control study. British Journal of Cancer 70 129132.CrossRefGoogle Scholar
Reddy, S, Sanders, TA, Owen, RW & Thompson, MH (1998) Faecal pH, bile acid and sterol concentrations in premenopausal Indian and white vegetarians compared with white omnivores. British Journal of Nutrition 79 495500.CrossRefGoogle ScholarPubMed
Refsum, H, Yajnik, CS, Gadkari, M, Schneede, J, Vollset, SE, Orning, L, Guttormsen, AB, Joglekar, A, Sayyad, MG, Ulvik, A & Ueland, PM (2001) Hyperhomocysteinemia and elevated methylmalonic acid indicate a high prevalence of cobalamin deficiency in Asian Indians. American Journal of Clinical Nutrition 74 233241.CrossRefGoogle ScholarPubMed
Renehan, AG, Zwahlen, M, Minder, C, O'Dwyer, ST, Shalet, SM & Egger, M (2004) Insulin-like growth factor (IGF)-I, IGF binding protein-3, and cancer risk: systematic review and meta-regression analysis. Lancet 363 346353.CrossRefGoogle ScholarPubMed
Rosell, M, Appleby, P, Key, T (2005 a) Height, age at menarche, body weight, and body mass index in life-long vegetarians. Public Health Nutrition 8 870878.CrossRefGoogle ScholarPubMed
Rosell, M, Appleby, P, Spencer, E & Key, T (2005 b) Weight gain over 5 years in 21 966 meat-eating, fish-eating, vegetarian and vegan men and women in EPIC-Oxford. International Journal of Obesity (In the Press).CrossRefGoogle Scholar
Rosell, MS, Lloyd-Wright, Z, Appleby, PN, Sanders, TAB, Allen, NE, Key, TJ (2005 c) Long-chain n-3 polyunsaturated fatty acids in plasma in British meat-eating, vegetarian, and vegan men. American Journal of Clinical Nutrition 82 327334.CrossRefGoogle ScholarPubMed
Sanders, TA (1999 a) The nutritional adequacy of plant-based diets. Proceedings of the Nutrition Society 58 265269.CrossRefGoogle ScholarPubMed
Sanders, TA (1999 b) Essential fatty acid requirements of vegetarians in pregnancy, lactation, and infancy. American Journal of Clinical Nutrition 70, Suppl. 555S559S.CrossRefGoogle ScholarPubMed
Sanders, TA, Ellis, FR, Dickerson, JW (1978 a) Studies of vegans: the fatty acid composition of plasma choline phosphoglycerides, erythrocytes, adipose tissue, and breast milk, and some indicators of susceptibility to ischemic heart disease in vegans and omnivore controls. American Journal of Clinical Nutrition 31 805813.CrossRefGoogle ScholarPubMed
Sanders, TA, Ellis, FR, Dickerson, JW (1978 b) Haematological studies on vegans. British Journal of Nutrition 40 915.CrossRefGoogle ScholarPubMed
Sanjoaquin, MA, Appleby, PN, Spencer, EA & Key, TJ (2004 a) Nutrition and lifestyle in relation to bowel movement frequency: a cross-sectional study of 20 630 men and women in EPIC-Oxford. Public Health Nutrition 7 7783.CrossRefGoogle Scholar
Sanjoaquin, MA, Appleby, PN, Thorogood, M, Mann, JI, Key, TJ (2004 b) Nutrition, lifestyle and colorectal cancer incidence: a prospective investigation of 10 998 vegetarians and non-vegetarians in the United Kingdom. British Journal of Cancer 90 118121.CrossRefGoogle Scholar
Scientific Advisory Committee on Nutrition (2003) Salt and Health. London: The Stationery Office.Google Scholar
Shetty, PS (2002) Nutrition transition in India. Public Health Nutrition 5 175182.CrossRefGoogle ScholarPubMed
Spencer, EA, Appleby, PN, Davey, GK & Key, TJ (2003) Diet and body mass index in 38 000 EPIC-Oxford meat-eaters, fish-eaters, vegetarians and vegans. International Journal of Obesity and Related Metabolic Disorders 27 728734.CrossRefGoogle Scholar
Stabler, SP & Allen, RH (2004) Vitamin B12 deficiency as a worldwide problem. Annual Review of Nutrition 24 299326.CrossRefGoogle ScholarPubMed
Steinfeld, H (2004) The livestock revolution – a global veterinary mission. Veterinary Parasitology 125 1941.CrossRefGoogle ScholarPubMed
Thomas, HV, Davey, GK, Key, TJ (1999) Oestradiol and sex hormone-binding globulin in premenopausal and post-menopausal meat-eaters, vegetarians and vegans. British Journal of Cancer 80 14701475.CrossRefGoogle ScholarPubMed
Waldmann, A, Koschizke, JW, Leitzmann, C, Hahn, A (2004) Dietary iron intake and iron status of German female vegans: results of the German vegan study. Annals of Nutrition and Metabolism 48 103108.CrossRefGoogle ScholarPubMed
Willett, W (1999) Lessons from dietary studies in Adventists and questions for the future. American Journal of Clinical Nutrition 78, Suppl. 539S543S.CrossRefGoogle Scholar
Williams, CM & Burdge, G (2006) Long-chain n-3 PUFA: plant v. marine sources. Proceedings of the Nutrition Society 65 4250.CrossRefGoogle Scholar
World Health Organization (2003) Diet, Nutrition and the Prevention of Chronic Diseases. WHO Technical Report Series no. 916. Geneva: WHO.Google Scholar