Soy's Negative Impact on The Thyroid
Soy's Thyroid Dangers
A Look at the Dangers of Soy to the Health of Your Thyroid
by Mary J. Shomon
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 possible substitute for hormone replacement, mean that soy products, while touted as foods and nutritional products -- often are used and act like a hormone.
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 metabolite 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 (TPO) 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."
Don't Go Overboard With the Soy Foods!
David Zava, Ph.D., a biochemist and an experienced breast cancer researcher stated in an interview:
"In studying the literature on soy I found there are about five types of plant chemicals [antinutrients] in the soybean that can be toxic to humans if they are not removed by special processing… the fifth antinutrient in soybeans is called a goitrogen.
This is a chemical that latches on to iodine, preventing it from absorbing into the body from the gastrointestinal tract. Iodine is needed to make thyroid hormone. Low thyroid function has been associated with poor brain development.
Anyone who has been deficient in thyroid hormone understands quite well what impact this can have on normal brain function, especially at a time in life as we grow older and "fuzzy thinking" creeps into our vocabulary."
North American Menopause Society Won't Endorse Soy Products
In a press statement, the North American Menopause Society has said:
"Our review found that scientific data are inconclusive regarding whether the observed health effects in humans are attributable to isoflavones alone or to isoflavones plus other components in whole foods… women may wish to consume whole foods that contain isoflavones, especially for potential cardiovascular benefits. However, scientific data supporting the use of isoflavones for hot flashes are conflicting, and inadequate data exist to evaluate their effect on breast and other female cancers, bone mass and vaginal dryness… Our evaluation also pointed out that a level of caution needs to be observed, especially in the use of isoflavone supplements, powders and pills…More studies documenting benefits and safety need to be conducted.''
Research Shows Soy's Effects
American Journal of Clinical Nutrition, Vol 68, 1431S-1435S:
"Effects of soy-protein supplementation on epithelial proliferation in the histologically normal human breast"
-- Study showed that short-term use of dietary soy stimulated breast cell proliferation, which can increase the risk of breast cancer.
Anti-thyroid isoflavones from soybean
November 1997 article from Biochem Pharmacol in which "it was observed that an … extract of soybeans contains compounds that inhibit thyroid peroxidase- (TPO) catalyzed reactions essential to thyroid hormone synthesis."
Breast and soy-formula feedings in early infancy and the prevalence of autoimmune thyroid disease in children
April 1998 article from the J Am Coll Nutr. that documents the association of soy formula feedings in infancy and autoimmune thyroid disease.
Leading Expert Warns of Soy-Thyroid Connection in Bestselling Book
In the bestselling book - "Living Well With Hypothyroidism: What Your Doctor Doesn't Tell You . . . That You Need to Know", leading soy expert Dr. Mike Fitzpatrick was profiled.
"Dr. Mike Fitzpatrick is an environmental scientist and phytoestrogen researcher who has extensively researched the issue of soy formulas, and the impact of soy consumption on thyroid function. Dr. Fitzpatrick introduced me to a little-known fact that can have substantial impact on people with hypothyroidism and the population in general -- overconsumption of soy products has the potential to impair thyroid function.
Dr. Fitzpatrick is so concerned that he is calling for soy formula manufacturers to remove the isoflavones -- the agents that are most active against the thyroid -- from their products.
There are also concerns for adult consumption of soy products. One UK study involving premenopausal women gave 60 grams of soy protein per day for one month. This was found to disrupt the menstrual cycle, with the effects of the isoflavones continuing for a full three months after stopping the soy in the diet.
Another study found that intake of soy over a long period causes enlargement of the thyroid and suppresses thyroid function. Isoflavones are also known to modify fertility and change sex hormone status, and to have serious health effects -- including infertility, thyroid disease or liver disease -- on a number of mammals… Dr. Fitzpatrick believes that people with hypothyroidism should seriously consider avoiding soy products, and predicts the current promotion of soy as a health food will result in an increase in thyroid disorders."
Soy Researcher is Even 'Very Concerned'
"There's a tendency in our culture to think if a little is good, then a lot's better," says Mary Anthony, a soy researcher at Wake Forest University School of Medicine in Winston-Salem, N.C. "But I personally am very concerned about isoflavone pills and soy protein supplemented with extra isoflavones."
Isoflavones, after all, seem to act like hormones or drugs in our body--even if for regulatory purposes they are classified as "Nutritional Supplements."