Soy Good - At least according to U of G Researcher

Thursday, November 16, 2006

Written by Kasia Kaluzny

Soy foods have recently received a great deal of attention because they contain isoflavones, which belong to the phytoestrogen class. Isoflavones are found almost exclusively in legumes, with soybeans having the most abundant source. Although isoflavones are strikingly similar in chemical structure to mammalian estrogens, they do not function in exactly the same way. Isoflavones from soybeans have been shown in many studies to prevent and/or treat the development of cancer, menopausal symptoms, heart disease, and osteoporosis. But can isoflavones have negative effects on men, such as interference with their normal reproductive hormones?

“There is no scientific basis for those claims,” says University of Guelph research Dr. Alison Duncan.

In her research, Duncan found that quite the opposite was true - soy consumption was beneficial to even healthy young males. Her studies carefully measured the levels of testosterone, estrogen, and other hormones in volunteers who consumed soy protein.

“The changes in these hormones were not to the extent that would have any effects on fertility,” Duncan reported.

Duncan’s research, published in a recent edition of the American Journal of Clinical Nutrition, has also shown that consumption of both low and high isoflavone-containing soy protein by men regulated the concentration of fats and cholesterol found in their blood in such a way to reduce the risk of cardiovascular disease.

The observation that Asian men who consume more soy have lower risk of developing prostate cancer prompted Duncan to also investigate this phenomenon in more detail. The study, published in 2005 in the Journal of Nutrition, was designed to examine the hormonal effects of soy protein consumption on healthy men aged 20-40 years. Results showed that soy protein has potential to contribute toward prostate cancer prevention. However, the study also indicated that more research needed to be conducted in order to gain a fuller understanding of how soy protein-induced hormonal changes relate to prostate cancer risk and what level of isoflavone consumption is most effective.

In the mean time, Duncan is actively promoting the health benefits of soy to both men and women, speaking to the public at the Royal Agricultural Winter Fair in Toronto last Saturday.

“I think that soy is a wonderful addition to a healthy diet,” said Duncan. “I would recommend that everyone consider adding soy to their diet.”

She explained that soy should not be the only food people eat, but that it is important to practice moderation and have a varied diet. Soybeans can be eaten cooked, or converted to other products such as soy sauce, miso, tofu, soy milk, flour, oil, as well as meat-mimicking products such as veggie dogs. Duncan claims that all these products can fit into an overall healthy diet that focuses on moderation and variety. Other beneficial properties of soybeans aside from isoflavones include their low fat, high protein, high fibre, and high vitamin B1 and B2 content.

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