Soy Estrogens- Are they a Protection Against Breast Cancer?

The Chinese say that breast cancer is a rich woman’s disease and indeed there is a very small incidence of it in China and Japan. Families in both countries eat a diet rich in soybeans and tofu. The health benefits of soy are  in isoflavones which are a class of plant estrogen found in a high concentration in soy. In particular genistein occurs in soy products such as tofu, soy protein isolates, soy flour and some estrogen dietary supplements.

The reason that genistein has come under medical scrutiny is the fact that it activates estrogen receptors in cells, including some types of breast tumor cells. Unfortunately clinical trials have been ambiguous, and in some cases extremely contradictory. Some concluded that female rats fed on genistein prior to puberty reduced the number of chemically induced mammary tumors. Other studies showed that estradiol, the primary human estrogen, encouraged the growth of existing estrogen-dependent breast tumors.

University of Illinois food science and human nutrition professor William Helferich, demonstrated that similar to estradiol dietary genistein stimulates the growth of estrogen responsive tumors and dietary genistein interfered with treatments, such as tamoxifen, that target estrogen receptors in breast tumors. As over two thirds of women with breast cancer have estrogen-responsive tumors, this has serious repercussions.

Helferich concluded that the difference was the timing exposure to genistein, an estrogen, before puberty causes mammary gland differentiation. Once a dell has become differentiated it is less prolific and less likely to develop cancer. However, if the estrogen is administered to an animal after the development of an estrogen-responsive tumor, the growth of this tumor will be stimulated.

This also has serious repercussions many women in their early to mid fifties are ingesting genistein and other isoflavones in supplements daily. They are marketed as a safe and natural alternative to the big bad HRT products, they are deemed so safe that they are more often than not sold without a doctor’s knowledge or prescription and yet women over fifty have an increased risk of developing breast cancer.

Helferich concluded that purified genistein is not as potent as HRT, it can be just as dangerous because it is often taken in higher quantities. To compound matters the components are not strictly regulated and can differ between batches. Genistein is only one component of the complete bean, whole soy beans have a wide variety of ingredients that are biologically active and they may have a cumulative effect which means that eating the whole can have a different effect from eating a small supplemental part.

All of this means that the sum of the nutrients in the whole bean is greater than that of the original parts combined; it is far cheaper to add whole soya beans to casseroles stews and soups than take expensive nutrient supplements.