Will eating soy increase my risk of getting cancer? What the current literature says.

Photo by Sherman Kwan on Unsplash

Soy and breast cancer

The impact of soy consumption on the incidence of breast cancer has been one of the most studied. In their systematic review and meta-analysis of 75 prospective studies examining the connection between various foods and breast cancer risk, Kazemi and colleagues (2021) identified seven studies with data on soy consumption for 4,055 breast cancer cases. The authors state that “soybean consumption was associated with a 3.5% reduction in breast cancer risk.” They note that this finding is consistent with those of other related studies, however the number of studies they worked with remains small and did not allow to differentiate between types of soy or women’s life stages (pre- or post-menopausal).

Soy and other cancers

Soy consumption also decreases the risk of prostate cancer, based on a systematic review and meta-analysis of 30 studies totaling over 250,000 individuals from Asia, North America, and Europe by Applegate and colleagues (2018). Among other findings, the authors calculated a 35 percent reduction of the risk of prostate cancer in those consuming more unfermented soy foods. However, the authors note that not all studies included in their meta-analysis took all confounding factors into consideration, and that some of the studies’ data could be inconsistent due to deficient participant recall.

Dietary guidelines

Thus, and though every study listed above has some limitations, there seems to be a consistent conclusion in the scientific literature: normal dietary consumption of soy food products, especially non-fermented ones like edamame, tofu, and soy milk, does not increase the risk of cancers occurring. Accordingly, the 2020 “Diet and Physical Activity Guideline” from the American Cancer Society encourages soy food consumption, as “soy and foods derived from soy are an excellent source of protein and thus provide a healthier alternative to meat.” The ACS however recommends avoiding soy-based supplements as they may be associated with higher cancer risk for certain women.

What about soy allergy?

You should know however that soy is considered a priority allergen (Health Canada, 2018). If you consume soy products (soy milk, tofu, edamame, vegan meats made with soy protein) and start experiencing a skin reaction, tingling (especially near your mouth), abdominal symptoms, or signs of anaphylaxis, you should get medical attention. However, an expert committee from the Food and Agriculture Organization of the United Nations is recommending that soy be moved to the “B list” of allergens as it impacts a very small number of people globally and generally causes mild symptoms only (FAO and WHO, 2022). Aside from being very nutritious, soy can be made into many delicious dishes and seasoned in a myriad of ways, so we would be foolish to go without.

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Brigitte Gemme

Brigitte Gemme

Vegan mom and cooking coach, runner, writer, reader, PhD in sociology, morning person. Chief Meal Planner at Vegan Family Kitchen.