Last May, 14 Hydroxycut products were recalled by the manufacturer, Canada-based Iovate Health Sciences, after the U.S. Food and Drug Administration (FDA) issued a warning to all consumers to stop using the supplements.
The warning was based on 23 reports to the agency describing liver damage in Hydroxycut users -- ranging from inflammation to tissue death severe enough to require a liver transplant. The supplement was also linked to one death.
Iovate said in May that it was recalling Hydroxycut because they "became aware that the U.S. Food and Drug Administration's assessment of 23 reports about consumers having experienced liver-related problems, as well as a small number of published case reports, was different from Iovate's analysis."
They noted that "the number of adverse event reports described by the FDA is small relative to the many millions of people who have used Hydroxycut products over the 7 years."
In the new study, reported in the American Journal of Gastroenterology, researchers analyzed 17 cases of liver damage among Hydroxycut users that had not yet appeared in the medical literature. Nine of the cases had been reported to the FDA, while eight were seen by the authors of the study.
Looking at factors like patients' risk factors for liver disease and the timing of their Hydroxycut use, the researchers found that for eight of the liver-damage cases, there was a greater than 95 percent likelihood that the weight-loss aid was to blame.
In five cases, the researchers concluded that Hydroxycut was "highly likely" the cause (a 75 to 95 percent chance), while it was probably to blame in two cases (a 50 to 74 percent chance). The last two cases were considered to be possibly linked to Hydroxycut use.
This type of study cannot definitively prove cause-and-effect -- something that is often "challenging" to do in cases where a drug is suspected of causing a toxic effect, noted study co-author Dr. Tse-Ling Fong, an associate professor of medicine at the University of Southern California, Los Angeles.
This is particularly true of dietary supplements, Fong told Reuters Health, because they do not have to be tested in clinical trials before going on the market, and little may be known about their potential for side effects.
In their analysis, Fong and three colleagues each independently assessed records from the 17 cases. That included eight patients who were treated at the researchers' respective medical centers between 2002 and 2009, and nine of the patients whose cases were reported to the FDA.
The researchers investigated the patients' medical histories and ruled out other causes of liver damage, like viral hepatitis or liver inflammation caused by an abnormal immune system reaction.
"Most people who take these weight-loss supplements are otherwise healthy," Fong noted, "and they are usually young." The average age of patients in this study was about 30.
The findings, according to Fong, strengthen the evidence that Hydroxycut itself has caused liver damage in some users.
They also show that some of that damage is severe, he noted. Of the 17 patients, three ended up needing a liver transplant and one died (the case previously reported to the FDA). The rest of the patients recovered from their symptoms, which included nausea, vomiting, abdominal pain and fatigue.
Fong said that the lesson for consumers is to be wary; dietary supplements, even ones touted as "natural," are not necessarily "safe."
"I think that consumers need to approach health supplements with caution," he said. "I would ask them to, before buying, try to look for scientific evidence that they are effective and safe."
The recalled Hydroxycut products contained a mix of herbs and other ingredients, like caffeine, and investigators have not yet determined which substances might be behind the liver damage.
Fong noted that shortly after the May recall, Hydroxycut's manufacturer came out with a "reformulated" weight-loss product called Hydroxycut Advanced -- which, the company says, now contains blueberry extracts, vitamin C and other antioxidants, plus caffeine as the "key" ingredient.
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