Millions of Americans have thyroid disease, and most of them are women, according to National Institutes of Health online medical encyclopedia Medline Plus. Because the thyroid gland produces hormones important for normal energy levels, metabolism and moods, hypothyroidism, which reduces its function, can trigger depression, lethargy and weight gain. An overactive thyroid, or hyperthyroidism, causes near-opposite symptoms, such as weight loss, anxiety and a rapid heartbeat. Although soy is nutritious, it can disrupt thyroid function in some people.
Basic Effect
Soy is a protein-rich legume that contains naturally occurring chemicals called goitrogens. While some goitrogens stimulate your body to produce antibodies that interfere with thyroid function, others interfere with an enzyme your body uses to add iodine during hormone production, according to Marcelle Pick, an obstetrician, gynecologist and co-founder of the Women to Women Clinic in Yarmouth, Maine. In both cases, goitrogens cause the thyroid to produce too few hormones, which play an important role in your metabolism, energy levels, body temperature and moods.
Healthy Reaction
If your thyroid gland functions normally, it compensates for reduced hormone production associated with goitrogens by producing more hormones. In other words, soy is unlikely to negatively effect your thyroid if you do not have a thyroid-related condition.
Negative Reactions
If your thyroid gland is underactive due to hypothyroidism, it may not be able to produce additional hormones after eating soy or other goitrogenic foods. In this case, soy can further impair thyroid function, increasing your risk for weight gain, according to a "Today's Dietitian" article published in October 2004. The goitrogens in soy may also interfere with thyroid medications.
Suggestions
There is no evidence that eating soy causes thyroid problems when it is incorporated into a well-balanced diet, according to registered dietitian Virginia Messina, an adjunct assistant professor at Loma Linda University. Because soy contains rich amounts of nutrients and provides a low-fat, cholesterol-free alternative to fatty protein sources, such as red and processed meats, moderate intake may enhance your wellness. To avoid thyroid complications, limit soy to one serving per day, which is equal to 8 oz. of soy milk, 2 tsp. of soy sauce or 4 oz. of tofu. For best results, seek specified guidance from your doctor or dietitian.
