Researchers purchased the 12 most popular dietary supplements for enhancing metabolism, promoting energy, easing so-called adrenal fatigue, or providing “adrenal support.” The adrenal gland makes hormones like cortisol, which helps regulate the metabolism and manage stress, and aldosterone, which controls blood pressure.
Lab tests of the supplements found they all contained thyroid hormone and most had at least one steroid hormone.
“Patients should be aware that any supplement that is sold as ‘natural,’ ‘organic,’ ‘herbal,’ ‘plant-based,’ may not be safe,” said lead author Dr. Halis Kaan Akturk of the Barbara Davis Center for Diabetes at the University of Colorado.
“These words and similar ones give patients a false reassurance,” Akturk, who did the study while at the Mayo Clinic in Jacksonville, Florida, said by email.
Taking too much thyroid hormone can lead to life-threatening heart problems, bone damage, excessive weight loss, tremors, and agitation, Akturk said.
Every supplement in the study contained a small amount of a thyroid hormone known as triiodothyronine.
In addition, seven of the supplements contained at least one adrenal or steroid hormone. The most commonly detected hormone was pregnenolone, which was in five supplements.
People who accidentally take adrenal or steroid hormone may experience symptoms like weight gain, hair loss, depression, acne, and stretch marks as well as a potentially life-threatening shutdown of the adrenal glands, Akturk said.
None of the products tested mentioned any thyroid or steroid hormones on their labels or on ingredient lists included with packaging materials, the study found.
The study wasn’t a controlled experiment designed to prove whether or how hormones hidden in dietary supplements might cause health problems.
It’s also not clear what dose of these hormones, over what period of time, might lead to side effects, said Dr. Pieter Cohen, a researcher at Cambridge Health Alliance and Harvard Medical School in Boston who wasn’t involved in the study.
“There is no question that if you take too much hormones they can have serious adverse effects,” Cohen said by email.
But the amounts in the supplements tested in the study might be too small to cause problems, Cohen said. Because the exact effect isn’t clear, patients should avoid these products, Cohen advised.