Specific Cancer Types
Analyses of the Oxford Vegetarian Study and EPIC-Oxford, and the Adventist cohorts with mean follow-ups ranging from 4.14 to 7.8 years, found no difference in cancer risk with a vegan diet compared with a nonvegetarian diet for colorectal, breast, gastrointestinal, respiratory tract, or urinary tract cancers.5-9 For breast cancer, an analysis of the AHS-2 found a nonsignificant trend toward a reduced cancer risk (HR, 0.78; 95% CI, 0.58-1.05; P = .09), but this trend was further shifted toward the null when adjusting for BMI (P = .25).8
The incidence of prostate cancer, however, was significantly reduced by 35% in the vegan cohort of the AHS-2 study compared with nonvegetarians (HR, 0.65; 95% CI, 0.49-0.85).10 When stratified by race, the benefit remained only for whites (HR, 0.63; 95% CI, 0.46-0.86), but was nonsignificant among blacks (HR, 0.69; 95% CI, 0.41-1.18), which may have been due to a small sample size (44 vs 15 events, respectively).
Adoption of a vegan diet may reduce the risk of developing cancer, but the data are inconclusive regarding specific cancer types. There are no data regarding whether the diet is an effective means of prevention among high-risk populations. A major limitation of the studies evaluating the effect of a vegan diet on cancer risk is the small sample size of vegans and the number of cancer events. There is no evidence of harm from following a vegan diet and it may be a healthy option for patients who properly plan meals. Clinicians should recommend that patients following special diets consult with a dietician to ensure the diet provides sufficient nutrition.
- Appleby PN, Key TJ. Conference on ‘The future of animal products in the human diet: health and environmental concerns’: Symposium 3: Alternatives to meat: The long-term health of vegetarians and vegans. Proc Nutrition Soc. 2016;75:287-293.
- Craig WJ, Mangels AR; American Dietetic Association. Position of the American Dietetic Association: vegetarian diets. J Am Diet Assoc. 2009;109(7):1266-1282.
- Melina V, Craig W, Levin S. Position of the Academy of Nutrition and Dietetics: vegetarian diets. J Acad Nutr Diet. 2016;116(12):1970-1980.
- Dinu M, Abbate R, Gensini GF, Casini A, Sofi F. Vegetarian, vegan diets and multiple health outcomes: a systematic review with meta-analysis of observational studies. Crit Rev Food Sci Nutr. 2017;57(17):3640-3649.
- Key TJ, Appleby PN, Crowe FL, Bradbury KE, Schmidt JA, Travis RC. Cancer in British vegetarians: updated analyses of 4998 incident cancers in a cohort of 32,491 meat eaters, 8612 fish eaters, 18,298 vegetarians, and 2246 vegans. Am J Clin Nutr. 2014;100(suppl 1):378S-385S.
- Le LT, Sabaté J. Beyond meatless, the health effects of vegan diets: findings from the Adventist cohorts. Nutrients. 2014;6(6):2131-2147.
- Orlich MJ, Singh PN, Sabaté J, et al. Vegetarian dietary patterns and the risk of colorectal cancers. JAMA Intern Med. 2015;175(5):767-776.
- Penniecook-Sawyers JA, Jaceldo-Siegl K, Fan J, et al. Vegetarian dietary patterns and the risk of breast cancer in a low-risk population. Br J Nutr. 2016;115(10):1790-1797.
- Tantamango-Bartley Y, Jaceldo-Siegl K, Fan J, Fraser G. Vegetarian diets and the incidence of cancer in a low-risk population. Cancer Epidemiol Biomarkers Prev. 2013;22(2):286-294.
- Tantamango-Bartley Y, Knutsen SF, Knutsen R, et al. Are strict vegetarians protected against prostate cancer? Am J Clin Nutr. 2016;103(1):153-160.