Their very name makes them sound like a healthy addition to any diet, but most supplements are unnecessary and some can even be dangerous, according to Harvard Medical School professor S. Bryn Austin,
Several supplements have been linked with an increase in certain cancers, for example, while others have been tied to an elevated risk of kidney stones. Although this research has been widely published, supplements continue to send roughly 20,000 people to the emergency room every year.
If you want to steer clear of the most dangerous types of supplements, you can start by avoiding three broad categories, says Austin, who spoke on a recent panel put on by The Forum, an event series organized by the Harvard T. H. Chan School of Public Health.
They are supplements related to weight loss, muscle building, and sexual performance, which Austin says are "the most lawless of all the categories and where the most problems turn up."
The problem isn't confined to the listed ingredients in these supplements, which can include everything from caffeine to herbal extracts derived from plants like wild mint and olive. The bigger issue is what may be in the product that's not on the label, says Austin.
"What we're concerned about is adulteration — where people are deliberately including ingredients that shouldn't be in there," Austin says.
The Food and Drug Administration keeps a list of all of the tainted products that have come under its radar. A large chunk of them are weight loss supplements. The illegal ingredients found in these pills and powders include things like the banned controlled substance sibutramine, which the FDA slashed from the market nearly a decade ago and the chemical phenolphthalein, which some research has suggested may be linked to cancer.
Some supplements even include prescription drugs with serious side effects. These drugs can also interact, in potentially deadly ways, with other medications.
"We know that these can be very toxic and have drug interactions," says Austin, adding that "weight loss supplements are making up a majority of events where people end up in emergency rooms."
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