Q: Can “thyroid support” supplements help me lose weight or give me more energy as claimed?
A: We strongly advise against them. Several years ago, a study in the journal Thyroid analyzed 10 commercial products and found that nine of them contained thyroid hormones (from animals), which are regulated as drugs by the FDA and are illegal in dietary supplements. (None of the labels declared the presence of the drugs.) At the recommended dosage, several of the supplements contained hormones at levels equal to or higher than that provided by prescription medication used to treat hypothyroidism (an underactive thyroid gland).
Moreover, the study found that many of the supplements contained high levels of iodine (from seaweed and other “natural” ingredients), which can also adversely alter thyroid function. And only half the supplements were labeled as containing bovine (cow) thyroid tissue, extract, or concentrate, which are sources of thyroid hormones.
Taking thyroid hormones when you don’t need them—and without being monitored medically with blood tests—can lead to severe hyperthyroidism and its associated deleterious effects, including heart palpitations and, over the long term, osteoporosis. That's because the hormones have a “narrow therapeutic margin” (meaning the dose at which beneficial effects occur is very close to the dose at which toxic effects occur). And unless you have hypothyroidism or take dangerously high doses, thyroid hormones will have little or no effect on your weight or energy level.
If you suspect you have an underactive thyroid—unexplained weight gain and fatigue are two possible signs—see your doctor. Never take thyroid supplements in lieu of proper evaluation and treatment.
This article first appeared in the UC Berkeley Wellness Letter.
Also see Is Thyroid Hormone Overused?