Soy Foods and Cancer
From the New York Times, August 30, 2023:
One historical worry about soy has been that its estrogen-like isoflavones might promote breast cancer, but many studies have shown that women who eat higher amounts of soy foods have no greater risk — or even a lower risk — of developing breast cancer than those who eat little or no soy, said Xiao-Ou Shu, a professor of epidemiology at Vanderbilt University School of Medicine.
The protective association is strongest in studies conducted in Asian countries, she noted, where soy is commonly consumed from infancy to old age.
In a study published in 2012, Dr. Shu and her colleagues found that among women in China and the United States who had been diagnosed with breast cancer, those who ate about half a serving or more of soy foods per day after their diagnoses were less likely to have a recurrence than those who ate smaller amounts.
Before this finding, Dr. Shu said, doctors had sometimes warned breast cancer patients to avoid soy foods. Today, the American Institute for Cancer Research says that “limited evidence” suggests that women who eat moderate amounts of soy may be more likely to survive — and perhaps have fewer recurrences of — breast cancer.
A moderate amount is defined as one to two servings of whole soy foods such as tofu, soy milk, edamame or soy nuts per day.
Some studies have also reported a protective effect of soy for prostate and lung cancers.
The American Cancer Society recommends soy foods and legumes as part of a healthy, balanced diet, but says that the evidence that soy foods in particular might protect people from breast or prostate cancer is “too limited to draw firm conclusions.”