Eating More Soy During Childhood May Decrease Breast Cancer Risk

Soy is considered a "superfood" by some nutrition experts and physicians. It's high in protein and low in fat and contains vitamins, minerals, and many other useful nutrients. It also has substances called phytoestrogens - plant-based estrogens - that can be useful for women during and after menopause.

High estrogen levels, though, have been associated with an increased risk of some types of breast cancer, especially when these levels occur in utero (to the fetus, not the mother) and after menopause. But there's new evidence that there may be other times of life when estrogens - in particular, those contained in soy foods - have the opposite effect.

It's been known for a while now that Asian women have a lower risk of breast cancer - at least until they move to the United States. Then their risk gradually increases over a period of years until it equals that of women born in the U.S. It was believed that the one of the factors contributing to this increased risk was the change in diet. And since there are more soy products consumed in Asia than in the U.S., it was theorized that soy might be contributing to the lower cancer risk of Asian women.

This theory seemed to be generally confirmed by a recent study of almost 600 Asian-American women. The women who ate a lot of soy foods between the ages of 5 and 11 had a 58% lower risk of breast cancer than those who didn't eat much soy during those years. Since soy contains estrogens, this seems to indicate that there are times when higher estrogen levels may actually help prevent the development of breast cancer, rather than contributing to it.

An earlier study, this one involving rats who were not yet into puberty, seemed to support this theory. The immature rats received genistein, an estrogen that comes from soy, and it did seem to decrease their cancer risk. One of the researchers who conducted this study suggested that it's possible that being exposed to estrogen in childhood may change the hormone receptors in breast tissue, making them less prone to develop hormone-related cancers later on in life.

But does this mean that it's useless to change your diet later in life if you want to prevent cancer? Doctors and nutritionists say no. Older research does show that eating more fruits, vegetables, whole grains, and beans - like soy - can reduce cancer risk at any age.

And soy contains more than just estrogens like genistein. It also has many cancer-fighting substances, including protease inhibitors, phytosterols, and saponins. So if you're interested in reducing your risk of cancer - especially if it runs in your family - you might want to consider adding some soy to your diet.