Consumers who buy Garcinia cambogia, a weight-loss supplement made popular by Dr. Oz, may not be getting what they expect, recent laboratory testing show.
Laboratory tests found 21 of 29 of the top-selling Garcinia cambogia supplements sold online contain substantially less of the active ingredient, called hydroxycitric acid (HCA), than the label claims.
The results were released by an independent supplement testing company, called LabDoor, and have not been subject to peer review, the primary process for vetting scientific results. In addition, several supplement safety researchers who Live Science contacted for comment on the study would not discuss the findings, either because they are not peer-reviewed or because their company prohibits them from commenting on weight-loss drugs. (Without peer review, there is very little way for researchers to assess the validity and reliability of the claims, one researcher said.) [Dr. Oz's Miracle Weight-Loss Pills: 5 Controversial Supplements]
Still, the results are consistent with those found by other independent labs that test supplements.
"I have seen substantial quality issues with Garcinia products and in some cases, there was not any HCA present in the products, while others had very low potency and a small number did meet label claim[s]," James Neal-Kababick, who was not involved in the new study, said in an email to Live Science. Neal-Kababick is the director of Flora Research Laboratories, a Food and Drug Administration-inspected testing lab in Oregon.
Even if the products did contain higher percentages of the active ingredient, there's little evidence that the supplement actually helps people lose weight, said Neil Thanedar, the CEO of LabDoor. (On its website, LabDoor includes links to all the Garcinia weight-loss supplements tested and receives a 10 percent commission on all products purchased through their site, Thanedar said.)
Wild West of supplements
Garcinia cambogia, or Malabar tamarind, is a small, pumpkinlike gourd that grows in Asia and is often used to add a sour tang to curries and other foods. However, in recent years, extracts of Garcinia have become extremely popular after Dr. Oz claimed the food had an almost miraculous ability to melt the pounds away.
But the evidence is scarce: In test tubes, the active ingredient, HCA, can convert fat into sugar, and in a few animal studies, animals taking the extract weighed less and ate less food than those not given HCA. But studies in humans have found conflicting results, with one study finding a slightly higher weight loss in groups taking HCA compared with those taking a placebo; another found no improved weight loss. And a 2014 case report in the journal Medical Toxicology showed that taking Garcina together with antidepressants can cause serotonin syndrome, a potentially life-threatening condition.
Dietary supplements like Garcinia exist in the shadow of FDA regulation. Supplements are not subject to the same regulation as drugs — there is no requirement that manufacturers prove they actually work, and companies are not required to get FDA approval before marketing their goods.
Supplements are required to be correctly labeled, and to not be adulterated; for example, they are not allowed to contain drugs that require a prescription. However, the FDA usually only tests a product if it hears of complaints or cases of injury or illness as a result of a supplement.
Label versus not
To evaluate what was really in products labeled as Garcinia cambogia, LabDoor tested 29 of the most popular Garcinia supplements found on sites such as Amazon, or stores such as Vitamin Shoppe and GNC. They used a test called high-performance liquid chromatography to separate out the HCA in each of the samples.
Most of the samples contained far less than the 1,000 milligrams considered to be an "active dose." In fact, some of the samples contained just 50 milligrams of HCA, Thanedar told Live Science.
For the worst performers, "What's interesting is that it's almost entirely filler," Thanedar told Live Science.
Though the company did not test the fillers, these can include common additives and ingredients used in pills, such as the gelatin for the capsules, cellulose (a plant material), starch or sugar, Thanedar said.
The company has submitted some of its findings to the Federal Trade Commission, which regulates false advertising, and some manufacturers have already taken Garcinia supplements off the market, Thanedar said.
The new findings aren't surprising, Neal-Kababick said.
"As supply catches up or exceeds demand, the products usually are less of an issue, but during high demand and short supply, there is an increased risk of fraud. In one case, we found only maltodextrin [an artificial sugar] in a product and no detectable Garcinia," Neal-Kababick said.
In addition, some of the methods that manufacturers may use to produce higher concentrations of HCA in a supplement can actually remove many of the "phytochemicals" that are normally found in the plant, he said. If that happens, the consumer is no longer getting a Garcinia extract, he said. (Phytochemicals are plant chemicals often responsible for color or smell, and some may be biologically active in the body.)
"What [consumers] are getting is a fractionated compound/purified compound of the botanical, which may not function the same as the botanical," Neal-Kababick said.
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Tia is the managing editor and was previously a senior writer for Live Science. Her work has appeared in Scientific American, Wired.com and other outlets. She holds a master's degree in bioengineering from the University of Washington, a graduate certificate in science writing from UC Santa Cruz and a bachelor's degree in mechanical engineering from the University of Texas at Austin. Tia was part of a team at the Milwaukee Journal Sentinel that published the Empty Cradles series on preterm births, which won multiple awards, including the 2012 Casey Medal for Meritorious Journalism.