Soy and A Healthy Thyroid

The thyroid gland is a small butterfly-shaped gland located under the Adam’s apple. Thyroid hormones affect all of the organs and cells in the body.

What Can Go Wrong with Thyroid Functions?

Thyroid dysfunction may be linked to hypothyroidism, hyperthyroidism, goiter, or thyroid cancer. In hypothyroidism, the thyroid produces too little hormone and leads to feeling cold or tired and having dry skin and hair, constipation, muscle cramps, or weight gain. Hyperthyroidism, when the thyroid produces too much hormone, is also known as Graves’ disease. Symptoms of hyperthyroidism include weight loss, nervousness, irritability, increased perspiration, a racing heart, hand tremors, anxiety, difficulty sleeping, increased bowel movements, fine brittle hair, and muscular weakness. Both hypo- and hyperthyroidism and iodine deficiency can enlarge the thyroid, called a “goiter.” Thyroid cancer is uncommon, accounting for less than 2% of all new cancer cases in the U.S. each year. According to the American Thyroid Association, people over the age of 35 should check thyroid hormone levels every five years.

Diet and Thyroid

Many plant foods contain goitrogens which may interfere with the function of the thyroid gland. Goitrogens are found in high-fiber foods, such as, whole grain breads and cereals, broccoli and cauliflower, as well as, iron and calcium supplements. Absent thyroid problems or iodine deficiency, no research suggests goitrogenic foods will negatively impact your thyroid health. In fact, the USDA/USHHS 2005 Dietary Guidelines encourage consuming more high fiber fruits, vegetables and legumes for their healthful properties.

Does soy cause thyroid disorders?

NO. A recent review of 14 clinical trials with healthy men and women concluded that consuming soyfoods or isoflavones had either no effects or only very modest changes within normal range of thyroid function. Participants in these trials consumed adequate amounts of iodine common in the American diet. In animal studies linking soy or isoflavone consumption to developing goiter, iodine deficiencies were present.

Iodine is Key

For healthy people, adequate iodine in the diet—150 micrograms per day—prevents goiter. Fortunately, iodine is easily obtained from iodized salt (a half-teaspoon of iodized salt provides 134 mcg of iodine), saltwater seafood, plants grown in iodine-rich soil, or products from animals that feed on these plants.

Can people with hypothyroidism eat soyfoods?

YES. Like other plant foods that contain goitrogens, soy can be part of a healthy diet. Those being treated for thyroid disorders need to discuss their diet with their physician and monitor levels of thyroid hormone in the blood to ensure that an appropriate level of medication is prescribed. Another strategy is to time the medication between meals, so that the chemical components in food do not interfere with the actions of the medicine.

Does soy cause thyroid cancer?

NO. A recent study indicates that eating soyfoods can actually protect against thyroid cancer in women. More research needs to be conducted to determine if these benefits are consistent in men and women.

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