| The Sweet Pea: Nutrition News You Can Use | |
by Kathy Early, from the June 2001 newsletter
Question: I have heard that soy foods can be bad for my thyroid. Should I
stop eating tofu and give up drinking soymilk?
Many claims are made regarding the nutritional and health effects of consuming soy foods (which includes soymilk, soy nut butter, roasted soybeans, tofu, and tempeh). Recently, there has been some talk of soy foods being harmful for thyroid function.
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For more information on the thyroid/soy connection, try… Thyroid Sourcebook: Everything You Need to Know, 3rd Edition. 1996 by M. Sara Rosenthal and Robert Volpe |
The thyroid is a butterfly-shaped gland located just below the Adam's apple in the neck and is responsible for many important body functions. The thyroid gland influences body weight, mental function, heart rate, bone formation, vision, menstrual regularity and many other body activities.
Thyroid disorders result in disturbances in normal body functioning. One of these disorders includes under-active thyroid, or hypothyroidism, the most common thyroid disorder. Hypothyroidism results in inadequate amounts of thyroid hormone being produced and can include symptoms of fatigue, mood swings, cold intolerance and dry coarse skin and hair. A second thyroid disorder is an overactive thyroid, or hyperthyroidism. Some symptoms of hyperthyroidism include irritability, nervousness, weight loss, sleep disturbances, vision problems and heat intolerance. The American Thyroid Association recommends all people over age 35 get a "Thyroid-Stimulating Hormone (TSH) Test" every five years to check thyroid function, just as you should have your cholesterol and blood pressure monitored.
Iodine is the mineral that the thyroid uses to make some hormones. Goiter, or enlargement of the thyroid, is characteristic of a thyroid problem. Goiters occur most commonly due to lack of iodine. However, goiters can also occur in many other cases of thyroid dysfunction even when iodine is present in adequate amounts.
Iodine is primarily found in the ocean, thus seafood and seaweed are excellent sources of iodine.
Iodine is also found in dairy products and foods grown in iodine-rich soils. In general, soils in older and more exposed regions are more iodine deficient. Regions of the Himalayas, the Andes and large parts of China are iodine deficient because iodine has been leached from these very old soils. The inland mountain areas of the US used to be prone to iodine deficiency, but this problem has great subsided with the use of iodized salt.
Iodized salt is optional here and used by about 50% of the US population. The salt-refining process results in the iodine being lost and this is why salt is available in iodized forms, where the iodine has been added back, and non-iodized forms. Iodized salt is mandatory in Canada.
Foods such as cruciferous vegetables (broccoli, cabbage, cauliflower, and Brussels sprouts), millet, and soybeans contain compounds called goitrogens. Goitrogens interfere with the absorption of iodine, which in turn limits the production of thyroid hormones.
To ensure you are getting enough iodine, you may want to consider consuming iodized salt, seaweeds, seafood or dairy foods. If you consume a large amount of soy foods, simply increase your use of iodine-rich foods. Years of research have examined the effects of soy foods on thyroid function and the results are clear: in those people with sufficient iodine intake, there is no reason to restrict soy food consumption. So enjoy!
Kathy Early RD, LD is a registered and licensed dietitian with particular interest in public health, wellness, and vegetarian nutrition issues.
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