Fat incinerator. Metabolism booster. Thermo activator. Some over-the-counter sports supplements advertise ingredients with purported performance-enhancing properties, but it’s anyone’s guess what’s really in that pill or powder.
Just 11 percent of nearly 60 tested dietary supplements actually contain an accurate amount of key ingredients listed on the label, scientists report July 17 in JAMA Network Open. Forty percent did not contain a detectable amount of the ingredients at all.
“I just had to shake my head,” says Pieter Cohen, a primary care doctor at Cambridge Health Alliance in Somerville, Mass. “It’s incredible that in 40 percent of the products, the manufacturer doesn’t even bother putting any [of the ingredient] in.”
Cohen and his colleagues chemically analyzed 57 sports supplements with labels that listed R. vomitoria, methylliberine, halostachine, octopamine or turkesterone — plants or plant compounds that could potentially serve as stimulants or muscle-builders. Only 34 contained the ingredient claimed. Six had about the right amount; 28 had inaccurate amounts that varied wildly, from 0.02 percent to 334 percent of the quantity indicated on the label.
“That’s alarming,” says Luis Rustveld, a dietician and epidemiologist at Baylor College of Medicine in Houston, who was not involved with the work. Some people may be very sensitive to these ingredients he says, and “they may be getting a whole lot more than they thought.”
Cohen’s team also found that seven of the products tested contained at least one compound prohibited by the U.S. Food and Drug Administration. In past years, scientists have identified hundreds of supplements tainted with potentially harmful drugs (SN: 10/12/18).
Unlike prescribed drugs, the FDA does not have the authority to approve dietary supplements before they hit grocery store shelves. But the agency requires that supplements do at least contain the ingredients they list on their label, Cohen says.
Just because a supplement is on the market does not mean it’s safe, effective or contains what it advertises, says Patricia Deuster, a nutrition specialist at the Uniformed Services University in Bethesda, Md., who did not participate in the new research. “It is virtually impossible for the average person … to make informed decisions about purchasing supplements without outside assistance.”
Third-party organizations like NSF, BSCG and USP can be helpful, she says, because they analyze supplements and offer their stamp of approval. And an online scorecard developed by the U.S. Department of Defense can also help consumers evaluate their supplements, Deuster says.
When deciding what and whether to buy, Cohen cautions, “you should use the utmost skepticism.” Rustveld agrees. “Whenever you see claims like, ‘You’re going to burn fat’, or ‘You’re going to improve your performance,’” he says, “if it sounds too good to be true, it’s probably not true.”