A low thyroid indicates that the thyroid, a gland located in your neck, is producing inadequate amounts of thyroid hormone---a condition called hypothyroidism. Hypothyroidism may be due to malfunctions of the pituitary gland, which secretes thyroid stimulating hormone; insufficient intake of iodine, necessary for the production of thyroid hormones; or diseases affecting the thyroid. Certain foods may inhibit enzyme activity in the thyroid, the uptake of iodine or the absorption of medications prescribed by your doctor.
Soy
Soy foods, derived from soybeans, provide many nutritional benefits. Soy also contains isoflavones---substances that affect the body in ways similar to those of the hormone estrogen. The capability of soy isoflavones to bind to estrogen receptors make soy a food of interest for researchers studying ways to reduce the risk of hormone-associated cancers such as breast cancer, describes the Linus Pauling Institute.
Research published by Evanthia Diamanti-Kandarakis and associates in the June 2009 issue of "Endorcrine Reviews" indicates that soy isoflavones inhibit thyroid function, however. To produce thyroid hormones, your body extracts iodine from foods with the help of the enzyme thyroperoxidase, or TPO. The researchers reveal that soy foods inhibit the activity of TPO, thereby reducing the amount of thyroid hormones produced. If you have low levels of thyroid hormone, you should avoid eating soy products.
Cruciferous Vegetables
Cruciferous vegetables are vegetables belonging to the Brassica family. Although rich in glucosinates---compounds that contain sulfur that may help protect cells from damage and prevent cancer---these vegetables also contain goitrogens. Goitrogens may interfere with the production of thyroid hormones, according to the Linus Pauling Institute. In addition, the glucosinates break down in your body and result in the production of thiocyanate ions. Thiocyanate ions compete with iodine for uptake by the thyroid gland. This competition can decrease iodine absorption and therefore decrease thyroid hormone production. If you have low thyroid production, you should avoid eating large amounts of cruciferous vegetables, which include broccoli, cauliflower, Brussels sprouts, cabbage, rutabaga, turnips, bok choy and collard greens.
Iron-Rich Foods
To treat hypothyroidism, doctors prescribe a synthetic thyroid hormone. The synthetic hormone replaces the missing hormones and helps reduce the fatigue, sensitivity to cold, depression, slow heart beat and constipation that often accompany hypothyroidism. The University of Maryland Medical Center indicates that iron, an essential mineral, may interfere with the absorption of synthetic thyroid hormones. If you are taking thyroid hormones, therefore, you should avoid eating iron-rich foods at the same time you take the medicine. Iron-rich foods include red meat, chicken, turkey and fish.
References
- The Endocrine Society "Endocrine Reviews": Endocrine-Disrupting Chemicals: An Endocrine Society Scientific Statement; E. Diamanti-Kandarakis, et al.; 2009
- Linus Pauling Institute: Isoflavones
- Linus Pauling Institute: Cruciferous Vegetables
- National Institutes of Health Office of Dietary Supplements: Iron
