U. S.-based soy detractors seem to have done an effective job in recent years
using the internet to spread myths about dangers of consuming too much soy.
They ve linked it to thyroid damage, reproductive difficulties and even dementia.
However, University of Guelph nutrition researchers say that making soy products
a regular part of a balanced diet will only improve your health.
Istvan Rajcan, professor and soybean breeding expert with the university s plant
agriculture department, says the misconceptions about thyroid and reproductive
problems being caused by soy consumption have developed because isoflavones
(phytochemicals naturally found in soybeans) are related to estrogens.
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The isoflavones in soybeans are a thousand times less potent than estrogen, so
one would have to consume huge amounts of soybeans to have any estrogen
effect, Rajcan says. A small percentage of the population has food allergies to
soy, but I have yet to see a study showing that an adult was negatively affected
from consuming too much soy.
Rather than doing people harm, soy isoflavones are known to offer some protection
against hormone-related disorders, including certain forms of cancer, says
Rajcan. Isoflavones have been shown to reduce prostate, breast and colon cancer,
to slow the onset of osteoporosis, and to alleviate symptoms of menopause.
In a study of the effects of consuming soy protein on reproductive hormones
related to prostate cancer risks in healthy adult men, University of Guelph human
nutrition researcher Alison Duncan found that some hormones actually reduced
risks of prostrate cancer. The research, published in the Journal of Nutrition, also
found that hormone levels remained within normal levels, not suggesting any negative
effects related to male fertility.
Duncan is also looking at the impact of soy on circulating thyroid hormones. My
research found no effects from soy consumption on thyroid hormones among
healthy young men, which adds to results from other studies that had similar findings,
Duncan says.
Duncan has also found that soy protein can reduce blood fats in healthy men, in
a direction that reduces the chances of cardiovascular disease, according to a study
recently published in the American Journal of Clinical Nutrition. Says Duncan: That
study showed that it s never too early to start incorporating soy into a balanced
diet and that there are benefits even for people who are healthy.
