The relationship between soyfoods and breast cancer risk has been a topic of research for more than 20 years. Evidence suggests that consuming modest amounts of soy during childhood and/or adolescence is very protective against breast cancer later on in life. But to the effects of soyfoods in women with breast cancer is controversial. In particular, there are questions about the safety of soy—especially soy supplements or extracts—for women with tumors that are stimulated by estrogen.
The latest study to provide insight into this issue was conducted by researchers from The Fred Hutchinson Cancer Research Center and the University of Washington (Seattle) and the University of California at San Diego.
In total, 35,016 female postmenopausal women between the ages of 50 and 76 years who were residents of Washington State were enrolled in the Vitamins And Lifestyle (VITAL) Cohort. Each participant completed a 24-page questionnaire that included questions about supplement use. Participants were followed for approximately 6 years. During this time 880 women developed invasive breast cancer.
Results showed that approximately 4.5% of the women reported using soy supplements. However, soy supplement use was unrelated to breast cancer risk; they neither increased nor decreased breast cancer risk. These results support other recently published research showing that soyfoods do not increase breast cancer risk in healthy women or women at increased breast cancer risk.
Brasky TM, Lampe JW, Potter JD, Patterson RE, White E. Specialty supplements and breast cancer risk in the VITamins And Lifestyle (VITAL) Cohort. Cancer Epidemiol Biomarkers Prev 2010;19:1696-708.