By Rachael Rettner, Senior Writer
Published: 11/20/2013 05:04 PM EST on LiveScience
Some popular weight-loss supplements contain a synthetic compound that is chemically similar to the drug amphetamine, according to a new study by researchers at the Food and Drug Administration.
However, the FDA has yet to take action regarding the findings, leading some scientists to criticize the agency.
In the new study, the FDA analyzed dietary supplements that were labeled as containing Acacia rigidula, a shrub native to Texas. Products whose labels claim to contain Acacia rigidula are commonly marketed for weight loss, supposedly by suppressing appetite and burning fat.
But 9 of the 21 dietary supplements tested were found to have an unnatural compound, called beta-methylphenethylamine, which is structurally similar to amphetamine. This compound has never before been tested in people, although animal studies suggest it may behave similarly to amphetamine, and could pose a public health risk, said Dr. Pieter Cohen, an assistant professor of medicine at Harvard Medical School and a general internist at Cambridge Health Alliance in Boston, who was not involved in the study. [Myth or Truth? 7 Ancient Health Wisdoms Explained]
The study was published last month in the Journal of Pharmaceutical and Biomedical Analysis, but an alert about these weight-loss products has not been issued to consumers.
"This is an outrageous situation, where the FDA's own in-house scientists are the ones who have discovered this, and shared it with the academic community," Cohen said. Consumers don't read scientific journals to find out drug safety information, he said.
"The FDA has to take aggressive, public action to alert consumers, and aggressive legal action againt the companies selling these products," Cohen said.
When asked whether the FDA has plans to alert consumers about the findings, Arthur Whitmore, an FDA spokesperson, said: "in response to the study findings the agency is contemplating appropriate follow-up steps, and at this time can not specify what those steps are."
Last month, Cohen and colleagues reported finding a methamphetamine-like compound, which had also not been tested in people, in the workout supplement Craze.
It's not clear how long manufacturers have been using Acacia rigidula in supplements (or labeling their supplements as containing the ingredient), Cohen said. At least six products sold at the nutrition retailer GNC contain Acacia rigidula, according to a search of the company's online store.
Cohen said that it's important to note that Acacia rigidula has never been used in herbal medicine or herbal remedies. That means that although the ingredient is "natural," it is illegal to use in any dietary supplements. If an ingredient does not have a history of being used as a supplement or herbal remedy, manufacturers must submit an application to the FDA for approval before using it in products.
In addition, the FDA analysis found many supplements labeled as containing Acacia rigidula didn't actually include this plant as an ingredient. The researchers compared the composition of dietary supplements labeled as containing Acacia rigidula with that of the plant itself.
None of the dietary supplements resembled Acacia rigidula in terms of their chemical composition. For example, nearly all of the supplements had high levels of a compound called phenethylamine, but this compound is found at very low levels in the plant itself.
"Given the low natural abundance of [phenethylamine] in the plant materials, it appears nearly impossible to achieve the amounts of [phenethylamine] found in the dietary supplements by formulating them with plant material or extracts of A. rigidula," the researchers wrote.
The relatively high levels of beta-methylphenethylamine found in nine of the supplements indicate that the ingredient was not an accidental contaminant, Cohen said.
"Basically, the label 'Acacia rigidula' is being used as a cover for introducing a brand new synthetic drug similar to amphetamine," Cohen said.
Amphetamines can make people feel energized, but also have serious risks, including addiction and increased risk of stroke, Cohen said. More studies are needed to determine the risks of beta-methylphenethylamine in people.
Because many weight-loss supplements have been found to contain illegal ingredients, people should avoid this class of supplements altogether, Cohen said. In light of the new findings, people should avoid supplements with Acacia rigidula, and if they experience side effects from supplements with this ingredient, they should notify their doctor, as well as the FDA, Cohen said.
Editor's note: This article was updated on Nov. 19 at 4 pm to include comments from the FDA.