The disease

Breast cancer is the most common type of cancer for women in Australia and New Zealand. It is caused by out of control growth of some of the cells of the breast. Some breast cancers will grow slowly and never cause problems, but others grow more rapidly and can be life-threatening.

In Australia, over 19,866 women were diagnosed with breast cancer in 2021, and 3,102 died from breast cancer. In New Zealand, on average 3,000 women are diagnosed each year and nine women will hear the news today that they have breast cancer.

The cause

There’s no single cause of breast cancer, although a healthful diet and lifestyle can help you reduce your risk of breast cancer, or make it less likely to come back if you’ve already been diagnosed.

The standard Western diet appears to play a major role in the development and progression of breast cancer. One important contributor (shared by what is often considered to be the male cancer equivalent, prostate cancer) is the effect of the Western diet on hormone levels, which the cells of the breast are particularly responsive to. Breast cancer rates are substantially lower in women in countries that do not traditionally consume the standard Western diet.

Also in Western countries, girls are starting their periods younger, and women are tending to go through menopause later, partly attributed to larger body mass. Fat cells produce oestrogen, the more fat cells you have, the more oestrogen your body makes. This means lifetime exposure to the female sex hormone oestrogen is extended, putting females at increased risk of hormone-dependent cancers.

Other lifestyle factors such as exposure to chemicals throughout your lifetime and drinking alcohol may all increase the duration and amount of breast cells’ exposure to oestrogen.

The nutrition prescription

Research indicates a whole food plant-based eating pattern may help prevent the development of breast cancer. It is likely that reduction in exposure to high levels of potentially cancer-promoting hormones, like oestrogen, across the lifespan will be responsible for a proportion of the benefit:

  • The association of six of the recommendations of the World Cancer Research Fund and American Institute for Cancer Research (related to body fatness, physical activity, foods that promote weight gain, plant foods, red and processed meats, and alcohol) with the incidence of invasive breast cancer was examined for 30,797 postmenopausal women. Breast cancer risk was reduced by 60% in women who met at least five recommendations compared with those who met none, and further analysis suggested that this reduction was due to meeting recommendations related to body fatness, plant foods and alcohol.[1]
  • Postmenopausal women in a trial who were overweight and obese and who followed a low fat predominantly plant-based diet in addition to regular moderate exercise demonstrated major reductions in breast cancer risk factors. Blood taken from these women two weeks after their changes was more effective at both suppressing the growth of and killing breast cancer cells in a laboratory setting than blood taken from the same women before the 2 weeks of diet and exercise.[2]

Recent research presented at the 2022 annual meeting of the American Society for Nutrition also showed that plant-based diets reduce the risk for breast cancer in postmenopausal women. Those women who followed a healthful, plant-based diet of fruits, vegetables, legumes, and whole grains the longest had the least risk of cancer compared to those who ate less healthy foods or animal products. Those who followed lower quality diets increased their risk for breast cancer.[3]


Medical supervision of diet change is essential

Shifting to a low fat whole food plant-based diet will often lead to rapid reductions in medication needs. Women who are on medications for high blood pressure especially should seek medical supervision.


Video overview from NutritionFacts.org

Further resources

PCRM logo

Physicians Committee for Responsible Medicine: breast cancer topic summary, resource kit based on a four-pronged lifestyle approach to reduce risk, and links to further articles.

Plant-based Health Professionals UK

Plant-based Health Professionals UK: further information on preventing and surviving breast cancer.

Nourish logo

Read our article, first published in Nourish Magazine, about the importance of nutrition to keep your hormones balanced. Written by Dr Gemma Newman, author of The Plant Power Doctor: A simple prescription for a healthier you.

FAQs

After a diagnosis of breast cancer, women who eat more soy-based foods actually have a better chance at a long, healthy life. They are less likely to have a recurrence and less likely to die from breast cancer than women who skip soy. The notion that soy products are associated with increased recurrence is a myth that has been widely and mistakenly promoted. Research findings show that eating soy foods like tofu, tempeh, and soy milk seems to have a protective effects.

Cow’s milk naturally contains stimulants for cell growth and division. These stimulants act in the body by raising levels of a growth factor called IGF1 (insulin-like growth factor 1). Studies show that in humans, it’s these raised levels of IGF1 that are strongly implicated in increasing breast cancer risk, which may be why drinking milk is linked to greater risk.

The vast majority of breast cancers are not due to genetic predisposition and lifestyle factors are clearly very important in a large number of cases. This has been shown by the increased incidence of breast cancer in Japanese women upon adoption of the Western diet and lifestyle.

While genes have been identified that increase risk, it is worth considering that lifestyle changes have been proven to alter genetic expression in the very similar ‘male equivalent’ of prostate cancer, in which the expression of approximately 50 cancer suppressing genes was increased and the expression of approximately 450 cancer promoting genes was decreased. The lead researcher of this work, Dr Dean Ornish, is renowned for the saying ‘Your genes are not your fate’, and it is highly likely that even women with a very high genetic risk of development of breast cancer will be able to have some control over their outcomes with appropriate lifestyle changes.

  1. Hastert TA, Beresford SA, Patterson RE, Kristal AR, & White E. Adherence to WCRF/AICR cancer prevention recommendations and risk of postmenopausal breast cancer. Cancer Epidemiol Biomarkers Prev, 2013 22(9), 1498-1508.
  2. Barnard RJ, Gonzalez JH, Liva ME, & Ngo TH. Effects of a low-fat, high-fiber diet and exercise program on breast cancer risk factors in vivo and tumor cell growth and apoptosis in vitro. Nutr Cancer. 2006 55(1), 28-34.
  3. Sanam Shah, Yahya Mahamat-Saleh, Wassila Ait-Hadad, Raphaëlle Varraso, Marie-Christine Boutron-Ruault, Nasser Laouali, Adherence to Healthy and Unhealthy Plant-Based Diets and Risk of Breast Cancer Overall and by Hormone Receptor and Histologic Subtypes Among Postmenopausal Women, Current Developments in Nutrition, Volume 6, Issue Supplement_1, June 2022, Page 253, https://doi.org/10.1093/cdn/nzac052.020

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