A Chinese study released earlier this month warned that people who take iodine supplements are in danger of developing subclinical hypothyroidism. But although the study itself was good, the researchers completely missed the mark when they interpreted the results, says Dr. David Brownstein, editor of The Natural Way to Health newsletter and board-certified family physician.
Iodine is needed by the body to make thyroid hormone. Subclinical hypothyroidism occurs when the body's levels of the thyroid hormone TSH increases slightly, but the person shows no obvious signs of the condition, such as weight gain, fatigue, depression, and dry skin. The recommended dietary allowance (RDA) for iodine is 150 mcg, but the National Institutes of Health says the safe upper limit is 1,100 mcg.
Iodine deficiency causes health problems from hypothyroidism and enlargement of the thyroid (goiter) to mental retardation in infants whose moms didn't get enough iodine during pregnancy. Falling thyroid levels cause hypothyroidism, but the new study concluded the exact opposite: The researchers decided that too much iodine — even as little as 400 mcg daily — can cause subclinical hypothyroidism.
"It was a good study, but the conclusion the researchers came to was terrible," Dr. Brownstein tells Newsmax Health. "I saw the Reuter's headline 'How Much Iodine is Too Much? ' and I immediately pulled the article and started dissecting it.
"The iodine study was a good, positive study," he said, "but unfortunately, the authors interpreted it wrong, and no one in the media picked up on it."
The four-week, double-blind, placebo-controlled study involved 256 adults with normal thyroid function. They were divided into 12 groups and were given daily iodine supplements ranging from 0 to 2 mg. "The scientists studied the effects of the differing doses of iodine by measuring thyroid function, thyroid size, and urinary iodine.
"The authors found that, as compared with the placebo group, all the iodine-supplemented groups responded with significantly increased urinary iodine excretion," he says. "Furthermore, the thyroid size decreased in the iodine-supplemented groups.
"These effects are exactly what you would expect when supplementing with iodine," he says. "A decreased thyroid size is, in fact, a good sign.
"The scientists also studied the thyroid function in the different groups," Brownstein says. "They found that the subjects treated with higher amounts of iodine had slightly elevated levels of thyroid stimulating hormone (TSH).
"They termed the subjects who had increased TSH levels as suffering from subclinical hypothyroidism," he says. "They concluded, 'This study showed that subclinical hypothyroidism appeared in the participants who (ingested 800 mcg iodine per day) … Thus we caution against a total daily iodine intake that exceeds 800 mcg/day.'
"Their interpretation was completely wrong," says Brownstein. "It is well-known and expected that when you put someone on iodine, TSH levels will slightly rise.
"The reason is that when you give iodine supplements to someone who is iodine-deficient, the body needs time to transport the iodine into other parts of the body, such as the breast or ovaries. TSH is needed to make the molecules — called sodium-iodide symporter (NIS) — that transports the iodine. So, the body increases the amount of TSH to make the transport molecules for iodine.
"The authors of the study concluded that the slightly elevated TSH confers a diagnosis of subclinical hypothyroidism," he says.
"Nothing could be further from the truth. It's not subclinical hypothyroidism — it's expected, it's normal, and it's a good thing. And the fact that the thyroid gland got smaller also showed the iodine was working."
Dr. Brownstein says the proper conclusion of the study should have read as follows: "This study showed, as expected, that iodine therapy resulted in a slightly elevated TSH. This would indicate that the subjects were properly producing NIS in order to transport iodine into the cell. Furthermore, as expected, iodine therapy appeared to improve the architecture of the thyroid gland by decreasing the thyroid gland volume as observed by ultrasonography measurement.'"
Dr. Brownstein's investigation led him to identify and name a new national illness — media-idophobia. "Media-iodophobia is an epic virus going around the country that happens when the news media reports a medical article about iodine in a negative light that causes anxiety and fear in the public," he says. That's what happened with this iodine story."
Editor's Note: Dr. Brownstein Explains Iodine and It's Anti-Cancer Benefits.