Goiter, iodine and thyroid health
DEAR DR. BLONZ >>
I was diagnosed with goiter after my recent annual checkup, and am now on low-thyroid medication. I was told to maintain a normal intake of iodine — there was no recommendation to take supplements. I try to eat healthy vegetables, but am now concerned that they can affect my thyroid. I typically use sea salt when I cook, if that makes a difference, but I would like to know more. — B.T., Greenville, South Carolina
DEAR B.T. >> The hormones thyroxine and triiodothyronine are produced by the thyroid: a butterfly-shaped gland in the front of the throat, above the voice box. These hormones regulate our metabolism, and iodine is an essential mineral in their structure. In essence: no iodine, no thyroid hormones.
When iodine is deficient, another gland, the pituitary, makes more of its thyroidstimulating hormone, or TSH, which can stimulate the thyroid to enlarge — ostensibly to do a better job of grabbing any available iodine in the body. A persistent iodine deficiency can result in a characteristic swelling in the throat area, which is something to see your health professional about.
Here is a relevant bit of history. Iodine is found in seawater, so crops grown near the coast tend to contain this mineral. Goiter based on iodine deficiency was not common in the United States' early years, as most lived near the coast. As populations moved west (but not as far as the Pacific coast), many settled in the country's midsection, where there was no dependable supply of dietary iodine. These regions were eventually nicknamed the “goiter belt” due to the more frequent incidence of iodine deficiency, with its noticeable bulge in the lower throat. In 1926, the government legislated that iodine be added to table salt as a public health measure, dramatically reducing the incidence of goiter. Iodine was the first nutrient substance purposefully added to foods.
Some vegetables, including cabbage, mustard greens, cauliflower and
Brussels sprouts, contain goitrogens: compounds that prevent iodine from being used by the thyroid gland. Goitrogens are not a concern unless the above foods are a significant part of your daily menu. Eating iodized salt or ocean fish are good ways to ensure an adequate intake of iodine.
Your health professional's recommendation to avoid iodine supplements is reasonable because today, regardless of whether they use iodized salt, it's rare for anyone eating a varied diet to suffer from an iodine deficiency. And as you use salt from the sea, it's likely that it already contains some iodine.
The Recommended Dietary Allowance, or RDA, for iodine is 150 micrograms daily for adults; it is considered a trace mineral. Iodized salt contains 45 micrograms of iodine per gram of salt, which means that the RDA for iodine can be met with just over one half-teaspoon. For more on diseases of the thyroid, see b.link/dzu2q7.