Good News about Soy and Breast Cancer

For years, doctors and scientists have fretted over whether to recommend soy foods to women at risk for breast cancer. On the one hand, we know these foods help to protect against heart disease. They do so mainly by providing a high quality source of protein without all the saturated fat and other toxins found in meat products. Soy foods may also improve LDL and HDL cholesterol numbers, especially in women. Yet there has been concern that because soy has "phytoestrogenic" properties, it might stimulate the growth of estrogen sensitive cancer cells. (By phytoestrogen, we mean a plant-based substance that has the ability to bind to estrogen receptors on our cells, thus potentially modifying the way the cell behaves).

In the past year, a number of very reassuring studies have been published that give us much more clarity about soy and breast health. The most notable comes from my alma mater, Vanderbilt University, and from the Shanghai Institute of Preventive Medicine. Researchers followed over 5000 Chinese breast cancer surivivors, ages 20-25, for nearly 4 years. They found that those women who included moderate amounts (more than 5.3 grams of soy protein) in their daily diets were about 30% less likely to have recurrence of breast cancer than those who avoided soy. In general, the more soy a woman ate, the healthier she was likely to be, regardless of whether her cancer was estrogen-sensitive or not. The researchers  were quick to make the point that they studied soy food intake, and not supplements, which have not been shown to have the same health benfits.

Researchers from Shanghai also followed younger, healthy women for more than 7 years, and found that those who chose more soy foods had about half the risk of developing breast cancer than those who preferred a meat-based diet. The same group found that a higher carbohydrate diet, especially starchy carbs, appeared to raise breast cancer risk in women uner 50.  In a similar vein, a study from Colorado State University in cooperation with USC, the University of Minnesota, and the National University of Singapore reported that a diet based on vegetables, fruit, and soy was associated with a 30% lower risk of breast cancer in post-menopausal women, when compared with a meat and starch diet.


In a separate study, researchers from USC reported that Asian American women who ate the most typical meat-and-potato Western diets had over twice the breast cancer risk as women who chose more soy foods and vegetables.

While we've known for years that soy is heart-friendly, these studies provide some much needed clarity on the subject of soy and breast health. As always, before you make a major change in your diet, it makes sense to talk with your doctor first.