Do Soy Foods Negatively Affect Your Thyroid?

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Do Soy Foods Negatively Affect Your Thyroid?

A Look at the Downsides of Soy

 

by Mary Shomon

 

It seems that there's isn't a newspaper, magazine or news program that

hasn't recently featured a story on the amazing health benefits of soy food

products and soy/isoflavone supplements. Soy is promoted as a healthy

alternative to estrogen replacement for some women, as a possibly way to

reduce the risk of breast cancer, as a way to minimize menopause symptoms,

and as a healthier, low-fat protein alternative for meats and poultry. But

what all the positive stories fail to mention is that there is a very

real -- but very overlooked -- downside to the heavy or long-term use of soy

products.

 

Soy products increase the risk of thyroid disease. And this danger is

particularly great for infants on soy formula.

 

This is not information that the powerful and profitable U.S. soy industry

wants you to know. The sale of soy products is big business, and the

increasing demand for soy protein products, soy powders and soy isoflavone

supplements is making that an even more profitable business than ever

before.

 

In researching my book, Living Well With Hypothyroidism, which covers the

issue of soy products and the thyroid in great depth, I talked to Dr. Mike

Fitzpatrick, an environmental scientist and phytoestrogen researcher who has

conducted in-depth studies on soy, particularly the use of soy formulas. Dr.

Fitzpatrick makes it clear that soy products can have a detrimental affect

on both adults and infants. In particular, he firmly believe that soy

formula manufacturers should remove the isoflavones -- that part of the soy

products that act as anti-thyroid agents -- from their products.

 

Researchers have identified that the isoflavones act as potent anti-thyroid

agents, and are capable of suppressing thyroid function, and causing or

worsening hypothyroidism. Soy is a phytoestrogen, and therefore acts in the

body much like a hormone, so it's no surprise that it interacts with the

delicate balance of the thyroid's hormonal systems. High consumption of soy

products are also proven to cause goiter, (Anti-thyroid isoflavones from

soybean: isolation, characterization, and mechanisms of action,Divi RL;

Chang HC; Doerge DR, National Center for Toxicological Research, Jefferson,

AR 72079, USA, Biochem Pharmacol, 1997 Nov, 54:10, 1087-96)

 

Note: The best source of information on soy and its negative impact on

health can be found at the Soy Online Service, and in particular, its page

on phytoestrogenic effects of soy, and impact on the thyroid.

 

Isoflavones belong to the flavonoid or bioflavonoid family of chemicals, and

are considered endocrine disrupters -- plants or other products that act as

hormones, disrupting the endocrine system, and in some cases, this

disruption involves acting as an anti-thyroid agent. (The grain millet, for

example, contains high levels of flavonoids, and is commonly known as

problematic for thyroid function). Flavonoids inhibit thyroid peroxidase

(TPO), which disturbs proper thyroid function.

 

The March 1999 issue of Natural Health magazine has a feature on soy that

quotes Daniel R. Doerge, Ph.D., a researcher at the Food and Drug

Aministration's National Center for Toxicological Research. Dr. Doerge has

researched soy's anti-thyroid properties, and has said " ...I see substantial

risks from taking soy supplements or eating huge amounts of soy foods for

their putative disease preventive value. There is definitely potential for

interaction with the thyroid. "

 

One UK study of 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. Isoflavones are also known to modify fertility and change sex

hormone status. Isoflavones have been shown 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 avoid soy

products, because, " any inhibition of TPO will clearly work against anyone

trying to correct an hypothyroid state. " In addition, he believes that the

current promotion of soy as a health food will result in an increase in

thyroid disorders.

 

The Dangers of Soy Formulas

 

Since the late 1950's, it has been known that soy formulas contain

anti-thyroid agents. Infants on soy formula are particularly vulnerable to

developing autoimmune thyroid disease when exposed to high exposure of

isoflavones over time. ( Breast and soy-formula feedings in early infancy

and the prevalence of autoimmune thyroid disease in children. Fort P; Moses

N; Fasano M; Goldberg T; Lifshitz F Department of Pediatrics, North Shore

University Hospital-Cornell University Medical College, Manhasset, New York

11030. J Am Coll Nutr, 1990 Apr, 9:2, 164-7) This study found that the

frequency of feedings with soy-based milk formulas in early life was

noticeably higher in children with autoimmune thyroid disease, and thyroid

problems were almost triple in those soy formula-fed children compared to

their siblings and healthy unrelated children. Dr. Fitzpatrick even believes

that long-term feeding with soy formulas inhibits TPO to such an extent that

long-term elevated TSH levels can also raise the risk of thyroid cancer.

 

Not much is being done in the U.S. to make parents aware of the

thyroid-related dangers of soy formulas, or to alert the public that heavy

soy consumption may be a danger to thyroid function. Other countries,

however, are far ahead of the U.S. In July of 1996, the British Department

of Health issued a warning that the phytoestrogens found in soy-based infant

formulas could adversely affect infant health. The warning was clear,

indicating that soy formula should only be given to babies on the advice of

a health professional. They advised that babies who cannot be breastfed or

who have allergies to other formulas be given alternatives to soy-based

formulas.

 

Why more information is not available about these concerns is probably a

function of the tremendous strength of the large agricultural companies that

dominate America's soy market. One thing is clear, however. At the same time

that health experts, and nearly every radio and television health program in

the nation touts soy as the miracle health food of the new millenium, the

United States pediatric and medical community needs to get more on top of

this issue, and begin to counsel their patients regarding the serious impact

use of soy products can have on thyroid function.

 

How Much Soy is Safe?

 

According to the Soy Online Service, for infants, any soy is too much. For

adults, just 30 mg of soy isoflavones per day is the amount found to have a

negative impact on thyroid function. This amount of soy isoflavones is found

in just 5-8 ounces of soy milk, or 1.5 ounces of miso. For more information

on how much soy is too much, see the Soy Online Service guidance page.

 

The USDA has launched a website that is promoting the health benefits of use

of soy and soy foods. The USDA site lists the isoflavone content of a total

of 128 foods, including foods such as vegetarian hot dogs soybeans,

chickpeas and tofu. This can help you in deciding how much soy to include in

your diet