From Mary Shomon,
Your Guide to Thyroid Disease.
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Health and nutrition magazines tout the benefits of soy as a cure-all for women's health, hormonal problems, cancer prevention, weight loss, and many other problems. The reality, however, is that promotion of soy may be more a matter of business and marketing, rather than recommendations based on sound scientific evidence.

Isoflavones, the key components of soy that make them so potent as a posible substitute for hormone replacement, mean that soy products, while touted as foods and nutritional products -- often are used and act as like a hormonal drug.

If you have a diagnosed or undiagnosed thyroid problem, or a history of autoimmune disease, overconsumption of soy isoflavones can potentially trigger a thyroid condition. Soy foods can worsen an existing diagnosed thyroid problem in many people. In both cases the symptoms such as fatigue, weight gain, and depression or moodiness are often overlooked and hard to diagnose.

A recent study found that as millions of Americans -- perhaps as many as more than 10 million -- have an undiagnosed thyroid condition. The vast majority of thyroid patients are women over 40. This is the same group that, responding to marketing claims that promote soy as helping to prevent breast cancer, reducing the risk of high cholesterol or heart disease, or as a treatment for symptoms of menopause, are turning to soy foods and isoflavone supplements in vast numbers.

Here is more information regarding soy and its relationship to the thyroid.

FDA's Soy Experts Speak Out Against Soy

"there is abundant evidence that some of the isoflavones found in soy, including genistein and equol, a metabolize of daidzen, demonstrate toxicity in estrogen sensitive tissues and in the thyroid. This is true for a number of species, including humans.

Additionally, isoflavones are inhibitors of the thyroid peroxidase which makes T3 and T4. Inhibition can be expected to generate thyroid abnormalities, including goiter and autoimmune thyroiditis. There exists a significant body of animal data that demonstrates goitrogenic and even carcinogenic effects of soy products. Moreover, there are significant reports of goitrogenic effects from soy consumption in human infants and adults."

Official Letter of Protest to the FDA Letter of protest from researchers Daniel Doerge and Daniel Sheehan, two of the Food and Drug Administration's (FDA) key experts on soy, to the FDA, protesting the health claims approved by the FDA on soy products

America's Foremost Alternative Doctor Warns Re: Soy

America's leading alternative doctor, Dr. Andrew Weil, has said about soy, at his Ask Dr. Weil website

"…you're unlikely to get too many isoflavones as a result of adding soy foods to your diet -- but you probably will take in too much if you take soy supplements in pill form. At this point, I can only recommend that you avoid soy supplements entirely."

Study Shows That Too Much Tofu Induces Brain Aging

From the Honolulu Star-Bulletin

"A Hawaii study shows a significant statistical relationship between two or more servings of tofu a week and 'accelerated brain aging' and even an association with Alzheimer's disease, says Dr. Lon White. "...these are not nutrients. They are drugs. They will have some benefits and some negative things."