Soyfoods lower risk of ovarian cancer
The American Cancer Society estimates that in 2014, about 21,980 American women will be diagnosed with ovarian cancer and about 14,270 women will die from this disease. Ovarian cancer ranks fifth in cancer deaths among women, accounting for more deaths than any other cancer of the female reproductive system. A woman’s risk of getting ovarian cancer during her lifetime is about 1 in 72. Her lifetime chance of dying from ovarian cancer is about 1 in 100.
There are considerable geographic variations in the incidence of ovarian cancer, with higher rates reported in developed countries. The age-standardized rates in Europe and the United States are 10.1 and 8.8 per 100,000 women, respectively, but only 3.8 per 100,000 women in China. The difference in incidence rates among countries has generated interest in the role of lifestyle in ovarian cancer. Unfortunately, there is little information about the relationship of diet to ovarian cancer risk, but new evidence suggests that soyfoods may be protective. Soyfoods are uniquely rich sources of isoflavones, which are plant estrogens that may have cancer-preventative properties.
Chinese investigators conducted an observational study which included 500 women with ovarian cancer and 500 women without the disease. Information on habitual consumption of soyfoods, including soybeans, soymilk, fresh tofu, dried tofu, and soybean sprouts, was obtained through interviews with the participants. Based on their intakes of soyfoods, the researchers were able to estimate their intake of isoflavones. A typical serving of traditional Asian soyfoods like tofu and soymilk provides around 25 milligrams of isoflavones. The women with ovarian cancer had lower average intakes of soyfoods than the women who didn’t have cancer. Average soy intake of the women with cancer was 75.3 grams per day compared to 110.7 grams for those who didn’t have cancer. When they were divided into three groups according to the amount of soy consumed, those in the highest intake group (≥120 grams per day) were 71% less likely to have ovarian cancer than women in the lowest intake group (<61 grams per day). Similarly, isoflavone intakes were inversely associated with the ovarian cancer risk, with significant dose-response relationships.
The especially good news from this study is that the amount of soy associated with protection against ovarian cancer is equivalent to only about one serving of soyfoods per day, such as one cup of soymilk, or ½ cup of edamame or tofu.
Andy H. Lee, Dada Su, Maria Pasalich, Li Tang, Colin W. Binns, Liqian Qiu. Soy and isoflavone intake associated with reduced risk of ovarian cancer in Southern Chinese women. Nutr Res 2014