Plant-Based Diets and the Link to Breast Cancer

Effects of the type of food being consumed and the risk of breast cancer is becoming ever more clear.  Several studies from this year and the past decade support this link.

 

The long-running Adventist Health Study-2 published their results in August 2025. For this huge report, encompassing almost 80,000 people from Canada and the USA, participants were assigned to one of the following dietary pattern groups based on the food they were eating (1);

• Vegan – those who avoided all animal products; implemented as less than 1 serving of an animal-sourced food a month
• Lacto-ovo-vegetarians – those who avoided all meat and fish but consumed eggs and dairy once a month or more
• Pesco-vegetarians – those who were lacto-ovo-vegetarians but also consumed fish once a month or more
• Semi-vegetarians -those who consumed meat and fish once a month or more but less than once a week.
• Non-vegetarians – those who consumed meat and/or fish once a week or more

NOTE: Vegetarians were defined to include the first 3 categories. Results for semi-vegetarians were not used as they were a small subgroup that did not clearly fit vegetarian or non-vegetarian categories

 Results (1) demonstrated that when comparing vegetarians (vegans, lacto-ovo-vegetarians and pesco-vegetarians) with non-vegetarians …

• Vegans showed a 24% reduction, lacto-ovo-vegetarians showed a 9% reduction, and pesco-vegetarians showed an 11% reduction in all cancers combined
• Vegetarians showed a 31% reduction in the risk of breast cancer in younger people
• Older vegans showed a 26% reduction in the risk of breast cancer
• Younger vegans showed a reduction in the risk of prostate cancer
• All vegetarian types including vegans showed a 21% reduction in the risk of colorectal cancer
• Vegan and lacto-ovo-vegetarians showed a 25% reduction in the risk of lymphoproliferative cancers (including lymphomas)
• All vegetarian types including vegans showed a 45% reduction in the risk of stomach cancer
• There was no evidence that a vegetarian or vegan dietary pattern increases the risk of any cancer

Researchers of this study wrote that it is perhaps no surprise that cancers of the gastrointestinal system appear to be more responsive to diets high in plant-sourced foods. The GI system comes into direct contact with food and its breakdown products after digestion as well as metabolites coming from the gut microbiome.  Processed meats are a well-known risk factor for colorectal and stomach cancer whereas higher intake of fruits and vegetables are protective. (1)

 

A more recent study, published in 2026, looked at cancer risk in meat eaters, poultry eaters, pesco-vegetarians, vegetarians and vegans from the UK, US, Taiwan and India. This investigation included cancers of the gastrointestinal tract, lung, reproductive system, urinary tract, and blood.  (2)

Results indicated that, when compared to meat eaters…

• Poultry eaters had 7% lower risk for prostate cancer
• Pesco-vegetarians had a 15% lower risk for colorectal cancer, a 7% lower risk for breast cancer and a 27% lower risk for kidney cancer
• Vegetarians had a 21% lower risk for pancreatic cancer, a 9% lower risk for breast cancer, a 12% lower risk for prostate cancer, a 28% lower risk for kidney cancer and a 31% lower risk for multiple myeloma
• Vegetarians displayed a 90% higher risk for squamous cell carcinoma of the oesophagus
• Vegans displayed a 40% higher risk for colorectal cancer.

Authors of this study discussed the mechanisms that may have led to these results.  They noted that the higher risk of colorectal cancer in the vegans is based on a very small number of cases and should be interpreted with caution as it is not compatible with the predicted reduction in risk due to the absence of meat intake.  In all cohorts studied, vegans had the lowest intake of alcohol (a known cause of colorectal cancer) and the highest intake of whole grains and dietary fiber which are highly associated with lower risk of colorectal cancer.  The authors suggest that nutrient deficiencies in vitamin B12, vitamin D, iron, calcium, zinc or iodine may be behind the increase in risk of colorectal and esophageal cancer seen in this report.  (2)

 

A systematic review of 17 previously-released papers was published in August, 2025.  (3) It found that replacing animal-based foods with plant-based foods could reduce the risk of developing breast or colorectal cancers, dying from cancer, or dying in general.  Investigators looked at the the risks of the development of cancer and its death rate when replacing animal-sourced foods (eggs, red meat, processed meat, poultry, fish and dairy products) with plant-sourced foods (fruits, vegetables, nuts, whole grains, soy and non-soy legumes).  Results showed that these food replacements were associated with reductions in the risk of breast and colorectal cancer and reductions in death from cancer and death from any cause.  (3)

 

A 2013 analysis of over 91,000 women from the California Teachers Study compared the effects of five different dietary patterns identified by their principal food components;  (4)

• A plant-based diet which was high in fruit and vegetables
• A high-protein high-fat diet which was high in meats, eggs, fried foods and high-fat condiments
• A high-carbohydrate diet which was high in convenience foods, pastas and bread products
• An ethnic diet which was high in legumes, soy-based foods, rice and dark-green leafy vegetables

 Results revealed that only the plant-based diet and the salad and wine patterns were associated with breast cancer risk overall (4).

• Consuming a plant-based diet was associated with a 15% reduction in breast cancer risk compared to eating the lowest amount of fruits and vegetables
• Consuming a salad and wine diet was associated with a 29% increase in the risk of breast cancer despite the presence of some healthy foods in this dietary pattern. The increased risk of breast cancer remained even after adjustment for alcohol consumption.

The authors of this study noted that the fiber component of fruit and vegetables as well as their high content of phytochemicals and antioxidants may be the source of protection against breast cancer.

 

A 2017 study from Taiwan indicated that vegetarians had less than half the odds of developing breast cancer compared to nonvegetarians.  (5)

 

A meta-analysis from 2015 revealed that eating one egg a day or five or more eggs per week increased the risk of breast cancer compared to not eating any eggs at all.  (6)

 

Earlier studies from 2002 showed that intakes of four or more vegetable dishes daily or a daily serving of beans or lentils were associated with cutting the risk of developing breast cancer in half.  (7)

 

In Canada, breast cancer is the 2nd most common cancer and 1 in 8 women will be diagnosed with breast cancer during their lifetime. (8)  In the US, the incidence of breast cancer rose by 1% every year between 2012 and 2021 and it continues to rise.  (9)  The simple choice of eating more plants and limiting animal-sourced foods is one way to diminish your risk of developing breast cancer.

 

 

SOURCES:

1  Fraser, G.E. et al. Longitudinal associations between vegetarian dietary habits and site-specific cancers in the Adventist Health Study-2 North American cohort.  American Journal of Clinical Nutrition. 122(2). pp. 535 – 543, Doi: 10.1016/j.ajcnut.2025.06.006, https://ajcn.nutrition.org/article/S0002-9165(25)00328-4/fulltext

2  Dunneram, Y., Lee, J.Y., Watling, C.Z. et al. Vegetarian diets and cancer risk: pooled analysis of 1.8 million women and men in nine prospective studies on three continents. Br J Cancer (2026). https://doi.org/10.1038/s41416-025-03327-4

3 C Fernández-Fígares Jiménez MDC, Storz MA. Cancer risk and mortality following substitution of animal foods with plant foods: a systematic review. Curr Nutr Rep. 2025;14(1):99. doi:10.1007/s13668-025-00688-3

4  Link, L.B., Canchola, A.J., Bernstein, L, et al. Dietary patterns and breast cancer risk in the California Teachers Study cohort. Am J Clin Nutr. 2013;98(6):1524-1532.

5  Chang, Y.J., Hou, Y.C., Chen, L.J., et al. Is vegetarian diet associated with a lower risk of breast cancer in Taiwanese women? BMC Public Health. 2017;17(1):800.

6  Keum, N., Lee, D.H., Marchand, N., et al. Egg intake and cancers of the breast, ovary and prostate: a dose-response meta-analysis of prospective observational studies. Br J Nutr. 2015;114(7):1099-1107.

7  Dos Santos Silva, I., Mangtani, P., McCormack, V., Bhakta, D., Sevak, L., McMichael, A.J. Lifelong vegetarianism and risk of breast cancer: a population-based case-control study among South Asian migrant women living in England. Int J Cancer. 2002;99(2):238-244.

8  https://www.canada.ca/en/public-health/services/publications/diseases-conditions/breast-cancer.html

9  https://www.cancer.org/research/acs-research-news/breast-cancer-incidence-still-rises-and-death-rate-still-declines.html