Photograph of bitter orange dietary supplements

Tests conducted by the Food and Drug Administration of several weight-loss dietary supplements revealed the presence of unapproved drugs, according to new study results released on the agency's website. But the FDA hasn't taken any enforcement action against the manufacturers of the products or warned consumers about them. 

The study, funded by the FDA and slated to publish in the journal Drug Testing and Analysis, analyzed the contents of 59 bitter orange supplements and found that about 10 percent contained the synthetic drugs methylsynephrine and isopropyloctopamine.

Bitter orange supplements are purported to suppress appetite and increase energy.

Methylsynephrine, also known as oxilofrine, is a stimulant that has been linked to nausea, vomiting, and cardiac arrest, and is considered a doping agent by the World Anti-Doping Agency. Methylsynephrine is used to treat low blood pressure in some countries, but it’s not approved for use in the U.S.

Isopropyloctopamine, or deterenol, is a compound that was never found to have a pharmaceutical use, and the FDA study says its “effects in humans are not known."

More on Supplements

Both ingredients, synthetic versions of a compound in the fruit of the bitter orange tree, “are not permitted in dietary supplements," the study says. 

“This new FDA study confirms another recent study demonstrating that experimental stimulants are widely available in many brands of dietary supplements,” says Pieter Cohen, M.D., an internist at Harvard Medical School who has studied supplements. “Inexplicably, the FDA has not warned consumers about their alarming findings.”

A spokesperson for the FDA, which regulates supplements in the U.S., says the purpose of the project was to develop and validate a method to analyze bitter orange supplements. 

"Projects like this generally are not designed to have a direct regulatory outcome," the spokesperson says, "but their findings can inform future compliance actions." The study's findings were shared with the FDA's Office of Dietary Supplement Programs, but no enforcement action has been taken to date, the spokesperson confirmed. The Agency wouldn't provide Consumer Reports with the names of products tested. 

Industry groups didn't respond directly to questions about the agency's inaction to date but say they support any effort by the FDA to clamp down on noncompliant manufacturers. 

“The mainstream dietary supplement industry is made up of responsible companies that adhere to regulations and are committed to providing consumers with safe, high-quality dietary supplements," says Andrea Wong, Ph.D., senior vice president of scientific & regulatory affairs at the Council for Responsible Nutrition.

The study also demonstrates the difficulty the FDA has in even tracking how many supplements are on the market today, because manufacturers are not required to register products before they put them up for sale. FDA researchers relied on the National Institute of Health’s Dietary Supplement Label Database to show how many bitter orange supplements are available today. But the paper concedes the database “does not capture all the products currently on the market.” 

“The FDA is tasked with ensuring that adulterated supplements are removed from the marketplace, but they have failed to act,” says Cohen, who has previously identified dietary supplements tainted with prescription drugs. “This has been a recurring problem over the past decade. The FDA's inaction raises the disturbing possibility that the supplement industry wields undue influence on the FDA's enforcement actions.”

Previous Warnings

In March 2016, the FDA warned several supplement manufacturers for selling products that contained methylsynephrine, saying it does not meet the statutory definition of a dietary ingredient. 

Before the agency’s new tests, other studies had confirmed the presence of methylsynephrine in some supplements, and several athletes have been banned from competitive sports after testing positive for the drug—which they claimed happened unwittingly as the result of taking supplements.

The FDA study says products it tested were purchased between June 2016 and November 2018. CR reviewed publicly available FDA enforcement data, including warning letters and safety advisories, and found none related to the drug in supplements since the March 2016 actions. 

The agency had also previously objected to the use of isopropyloctopamine in supplements. The study notes that the ingredient was cited in a 2013 advisory from authorities in the Netherlands, who warned consumers to not take a particular supplement containing it because it was associated with severe adverse events that led to heart problems and cardiac arrest

The agency has yet to take any enforcement action or issue public statements about the potential risks of isopropyloctopamine in supplements, according to CR’s review of enforcement data.

Inaction Isn't New

The FDA has previously been criticized for failing to act on its own test results. In a 2013 FDA study, an unapproved amphetamine-like substance known as BMPEA was found in Acadia rigidula supplements, also marketed for weight loss. Two years later, in 2015, Harvard’s Cohen co-published a study that found the same thing.  

“More than two years after the FDA’s discovery, the FDA has yet to warn consumers about the presence of the amphetamine isomer in supplements,” Cohen wrote in his study. 

Weeks later, the agency issued warning letters to several manufacturers for making supplements that included BMPEA.

What You Can Do

Industry groups support increased funding for the FDA, to improve oversight of supplements, including mandatory registration of products. 

"As we work across the industry and with members of Congress to improve DSHEA [the acronym for the 1994 law that put dietary supplements under FDA oversight], we will support these additional resources as well as formalizing product registration," says John Troup, Ph.D., vice president of scientific affairs and dietary supplements at the industry group Consumer Healthcare Product Association.

In the meantime, see Consumer Reports' advice on how to shop smarter for supplements.

And if you have an adverse event after taking a supplement, seek medical attention right away.

Then you should file a report about the incident with the FDA, which maintains a database to collect such events, and encourage your healthcare provider to do so as well. You and your provider should also contact the manufacturer, which is required to tell the FDA about it if the event is serious.

Consumers should also consult with their primary care doctor if they’re taking a supplement. The supplement could have potentially adverse interactions with medications you are taking.

And if you’re thinking about taking a supplement, consult with reliable, trustworthy resources, such as the NIH’s health portal, for consumers to fully understand the product’s potential benefits and risks.