The Cancer Research
There’s not really research about “flexitarian diets” and cancer risk, in part because they are “flexible” and can be accomplished in many different ways. This is one option for creating a plant-based diet, which is the kind of eating pattern recommended for lower risk of cancer and heart disease.
- Limited evidence suggests that high-fiber diets rich in whole grains, non-starchy vegetables, and fruits reduce risk of a wide range of cancers. Healthy dietary patterns linked with lower cancer risk also limit consumption of alcohol and of red and processed meats.
- In a major U.S. study of different types of vegetarian and non-vegetarian diets, people classified as “semi-vegetarian” who ate meat and fish up to once a week did not show any difference in overall cancer risk, or risk of particular types of cancer, compared to non-vegetarians. It is important to note that in this study, non-vegetarians included meat and fish an average of three times a week and ate a generally healthy diet. So these results can’t be interpreted as a comparison with non-vegetarians who eat large amounts of meat and an overall unhealthy diet.
Interpreting the data
After a systematic review of the global scientific literature, AICR/WCRF analyzed how a variety of plant foods and their nutrients affect the risk of developing cancer.
- Evidence categorized as “probable” means there is strong research showing a causal relationship to cancer—either decreasing or increasing the risk. The research must include quality human studies that meet specific criteria and biological explanations for the findings.
- A probable judgement is strong enough to justify recommendations.
- Evidence categorized as “limited suggestive” means results are generally consistent in overall conclusions, but it’s rarely strong enough to justify recommendations to reduce risk of cancer.
Source: AICR/WCRF. Diet, Nutrition, Physical Activity and Cancer: A Global Perspective, 2018.
Ongoing Areas of Investigation
- More on Flexitarian Diet
What you do eat as well as what you don’t eat counts: Studies of plant-focused diets and their association with cancer risk sometimes show different results. A closer look suggests that part of the difference may reflect the importance of specific food choices.
- All plant foods are not the same. Aim to include several servings of whole grains daily, and eat a variety of vegetables and fruits for the widest array of nutrients and protective phytochemicals. The average American diet is much lower in fiber than amounts recommended for lower risk of colorectal cancer, and all these plant foods, as well as legumes, nuts and seeds, can help you reach recommended levels.
- If you include red meat occasionally, be sure that it’s mostly unprocessed red meat. Processed meats (like bacon, sausage, salami and hot dogs) pose greater cancer risk, so it’s best to save them for much more occasional use.
- Eating patterns are an important part of a lifestyle to reduce cancer risk, but there’s much more you can do. Be physically active in some way every day, limit time you spend sitting, aim to reach and maintain a healthy weight, limit alcohol, and of course, avoid tobacco in any form.
- World Cancer Research Fund/American Institute of Cancer Research. Continuous Update Project Expert Report 2018. Recommendations and public health and policy implications. Available at dietandcancerreport.org.
- Scientific Report of the 2015 Dietary Guidelines Advisory Committee. Washington, DC.2015.
- Arnett D, K., Blumenthal Roger S, Albert Michelle A, et al. 2019 ACC/AHA Guideline on the Primary Prevention of Cardiovascular Disease. Circulation.0(0):CIR.0000000000000678.
- World Cancer Research Fund / American Institute for Cancer Research. Continuous Update Project Expert Report 2018. Wholegrains, vegetables and fruit and the risk of cancer. Available at: dietandcancerreport.org.
- 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.
- Orlich MJ, Chiu THT, Dhillon PK, et al. Vegetarian Epidemiology: Review and Discussion of Findings from Geographically Diverse Cohorts. Advances in Nutrition. 2019;10(Supplement_4):S284-S295.
- World Cancer Research Fund/American Institute of Cancer Research. Continuous Update Project Expert Report 2018. Meat, fish and dairy products and the risk of cancer. Available at: dietandcancerreport.org.