A study from the USA was released Feb 25 showing that consuming up to 1/2 serving of soyfoods per day did not increase breast cancer recurrence among women previously diagnosed with breast cancer, and was even associated with lower mortality among such women.

The Women’s Healthy Eating and Living (WHEL) study is a randomized controlled trial of a high fruit/vegetable/fiber and low fat dietary intervention in early stage breast cancer survivors in the USA. It had a median follow-up of 7.3 years from the time of enrollment. Soy intake was measured post-diagnosis (median 2 years, range: 2 months to 4 years) using a food frequency questionnaire that included specific items for “Meat Substitutes (such as Tofu, Veggie Burgers),” and “Soy Milk”, as well as an opportunity to include other soy foods and supplements.

Isoflavone intake (the marker for soy) was unrelated to the risk of recurrence regardless of hormone receptor status or Tamoxifen use. No significant increased or decreased risk was associated with any specific level of intake. Risk of death tended to be lower as isoflavone intake increased (p for trend=0.02). Women at the highest levels of isoflavone intake (>16.3 mg/day isoflavones; equivalent to at least 1/2 cup soymilk or 2 oz tofu) had a non-significant 54% reduction in risk of death compared to the lowest quintile of soy intake.

The authors state:

Our study is the third epidemiological study to report no adverse effects of soy foods on breast cancer prognosis. These studies, taken together, which vary in ethnic composition (two from the US and one from China) and by level and type of soy consumption, provide the necessary epidemiological evidence that clinicians no longer need to advise against soy consumption for women diagnosed with breast cancer.

Reference

Caan BJ, Natarajan L, Parker BA, Gold EB, Thomson CA, Newman VA, Rock CL, Pu M, Al-Delaimy WK, Pierce JP. Soy Food Consumption and Breast Cancer Prognosis. Cancer Epidemiol Biomarkers Prev. 2011 Feb 25. Link

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