Skip to main content

Vegetarian diets and cancer risk

The Original Article was published on 24 February 2022

The Original Article was published on 24 February 2022


Vegetarian diets contain vegetables, fruits, whole grains, legumes, nuts, and seeds [1]. They are devoid of flesh foods (such as meat, poultry, wild game and their products) and may or may not include eggs and dairy products (vegan diet) [1]. A pescatarian diet is a vegetarian diet that includes fish and is devoid of flesh foods [1]. In many countries, the number of people who adopt a vegetarian diet is increasing, and there are several main reasons for this [2]. Ethical concerns about animal welfare and environmental sustainability motivate the adoption of a vegetarian diet [3]. Vegetarian diets are associated with increased environmental sustainability through reduced greenhouse gas emissions, deforestation and water use [4]. Health improvements and weight loss are other strong motivators for the adoption of a vegetarian diet [3]. According to the Academy of Nutrition and Dietetics of the USA, vegetarian diets are associated with better health outcomes, an increased life expectancy, and a reduced risk of coronary heart disease, type 2 diabetes, hypertension and obesity [1]. Furthermore, vegetarian diets are also considered to reduce the risk of certain types of cancer [1].

Vegetarian diets and cancer

Previous studies on the association of dietary patterns and specific types of cancer led to partially conflicting results. The pooled analysis of data obtained from the Oxford Vegetarian Study and the EPIC-Oxford cohort, including 61,647 participants, revealed that vegetarians and pescatarians have an overall reduced risk of developing cancer compared to meat eaters [5]. Additionally, the database study also identified a reduced risk of stomach cancer, cancers of the lymphatic and haematopoietic tissue and multiple myeloma among vegetarians and pescatarians and a reduced risk of colorectal cancer among pescatarians [5]. Based on 69,120 participants, the Adventist Health Study-2 revealed that vegetarians were protected from cancers of the gastrointestinal tract compared to nonvegetarians [6]. A vegan diet reduced the overall cancer incidence and the risk of female-specific cancers [6]. In contrast, a recent meta-analysis that included nine studies did not identify any benefit of a vegetarian diet on the risk of breast, colorectal or prostate cancer [7]. Another recent meta-analysis attributed a reduced risk of cancer mortality to a vegetarian diet without showing any association between diet and a specific type of cancer [8].

The reports presented by Parra-Soto et al. [9] and Watling et al. [10] are based on 409,110 and 472,377 UK Biobank participants, respectively, recruited between 2006 and 2010. The mean follow-up was 10.6 and 11.4 years [9, 10], respectively. To date, both papers represent the largest database studies ever to address the question of vegetarian and pescatarian diets and the risk of cancer. The design and results differ substantially in some aspects between both studies. In contrast to Parra-Soto et al. [9], Watling et al. [10] distinguished between regular and low meat eaters as those who consume processed, red meat (beef, pork, lamb) or poultry >5 or ≤5 times a week, respectively. Low meat eaters had a reduced risk of colorectal cancer compared to regular meat eaters [10]. Vegetarians had a lower risk of all cancers, prostate cancer and postmenopausal breast cancer, and pescatarians had a lower risk of all cancers than regular meat eaters [10]. The authors indicated that the reduced risk of postmenopausal breast cancer may be largely attributed to the lower mean body mass index (BMI) of vegetarian women. The authors also performed subgroup analysis for sex and smoking. After removing lung cancer cases from the analysis, the reduced risk of all cancers for vegetarians, pescatarians and low meat eaters was only found among ever-smokers [10]. Furthermore, a reduced risk of colorectal cancer among dietary groups compared to regular meat eaters was only found among men [10].

Due to the exclusion of all participants with cancer at baseline and those with missing data about diet and important covariates, the study group of Parra-Soto et al. [9] was smaller. Meat eaters form a single group, and the results are also represented for a separate dietary group of fish-poultry eaters [9]. In their maximally adjusted model, vegetarians had a lower risk of all cancers, and prostate cancer and pescatarians had a lower risk of all cancers than regular meat eaters [9]. In contrast to the study of Watling et al. [10], vegetarians did not have a reduced risk of breast cancer but did have a reduced risk of colorectal cancer [9]. Furthermore, pescatarians also had a reduced risk of melanoma [9]. Additionally, in a meta-analysis, authors pooled their UK Biobank data with eight prospective cohort studies [9]. In the pooled analysis, vegetarians and pescatarians had a reduced risk of all cancers and a borderline reduced risk of colorectal cancer [9].


The different outcomes of the two studies are explained by varying sample sizes, categories of diet groups and distinct modelling strategies. The subgroup analysis in one study indicated that important additional variables, such as smoking, can modulate the risk of cancers and can confound the results of dietary cancer associations. Both papers are based on large datasets and undoubtedly reveal that vegetarian diets can indeed decrease the risk of specific types of cancer. The risks of prostate cancer and colorectal cancer among men are decreased by a vegetarian diet. In the case of postmenopausal breast cancer, the protective effect may be an indirect one that acts through the modification of the BMI. The diet may only have an impact on certain types of cancer, as neither study detected any effect of the vegetarian diet on the risk of lung cancer. However, the protective effects of vegetarian diets on rare types of cancer may not have been detected in these studies because the numbers of affected patients were low. It is predictable that future studies will probably reveal further associations between vegetarian diets and risk reduction in other cancer types.

Availability of data and materials

Not applicable


  1. Melina V, Craig W, Levin S. Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. J Acad Nutr Diet. 2016;116(12):1970–80.

    Article  PubMed  Google Scholar 

  2. How many adults in the U.S. are vegetarian and vegan? How many adults eat vegetarian and vegan meals when eating out? []

  3. Hagmann D, Sigrist M, Hartmann C. Meat avoidance: motives, alternative proteins and diet quality in a sample of Swiss consumers. Public Health Nutr. 2019;22(13):2448–59.

    Article  PubMed  Google Scholar 

  4. Fresán U, Sabaté J. Vegetarian Diets: Planetary Health and Its Alignment with Human Health. Adv Nutr. 2019;10(Suppl_4):S380–8.

    Article  PubMed  PubMed Central  Google Scholar 

  5. 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–85S.

    Article  CAS  Google Scholar 

  6. 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):286–94.

    Article  PubMed  Google Scholar 

  7. Godos J, Bella F, Sciacca S, Galvano F, Grosso G. Vegetarianism and breast, colorectal and prostate cancer risk: an overview and meta-analysis of cohort studies. J Hum Nutr Diet. 2017;30(3):349–59.

    Article  CAS  Google Scholar 

  8. 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. 2017;57(17):3640–9.

    Article  Google Scholar 

  9. Parra-Soto S, et al. Association of meat, vegetarian, pescatarian, and fish-poultry diets with risk of 19 cancer sites and all cancer: Findings from the UK Biobank prospective cohort study and meta-analysis. BMC Med. 2022.

  10. Watling CZ, et al. Risk of cancer in regular and low meat-eaters, fish-eaters, and vegetarians: a prospective analysis of UK Biobank participants. BMC Med. 2022.

Download references

Data share statement

Not applicable


Not applicable

Author information

Authors and Affiliations



The author(s) read and approved the final manuscript.

Corresponding author

Correspondence to Mathias Weller.

Ethics declarations

Ethics approval and consent to participate

Not applicable

Consent for publication

Not applicable

Competing interests

The author declares no competing interests.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Weller, M. Vegetarian diets and cancer risk. BMC Med 20, 81 (2022).

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: