In the first review of the literature on clinical trials of herbal dietary supplements for weight loss in 16 years, scientists have concluded that these supplements are ineffective and their use cannot be justified by modern scientific methods. Plant-based dietary supplements cause only modest weight loss, even compared with placebo, and have no health benefits, scientists have concluded. Now researchers are calling for the long-term effects of supplements on health to be studied.
Recently, the global industry of plant- or animal-based bioactive supplements has grown significantly. By 2020, it is estimated to be worth $41 billion. Meanwhile, only 20% of new drugs entering the market are tested to see how well their claims match up with actual results. In some countries, the only regulatory requirement for dietary supplements is a certain level of non-medical ingredients. Unlike drugs, dietary supplements do not need to be proven safe and effective in clinical trials before they can be marketed, says lead study author Erica Bessel of the University of Sydney.
“After careful analysis of all the available data, we have concluded that we cannot recommend these drugs for weight loss,” she says. “Although most drugs appear to be safe in the short term, they do not lead to clinically significant weight loss,” the researcher adds. We explain quickly, simply, and clearly what happened, why it matters, and what happens next. Episodes End of story Podcast advertising Australian scientists systematically analyzed all tests of dietary supplements conducted before 2018 in which they were compared to placebos or dummy drugs. The comparative review included 54 trials with 4331 participants over the age of 16. Doctors consider a weight loss of 2.5 kilograms to be “clinically significant”.
Supplements based on a variety of botanicals have been tested – green tea, Cambodian garcinia, white kidney bean, juniper, African mango, yerba mate, four-leafed cissus, licorice root, and East Indian fleabane. Only three extracts were found to be statistically (but not clinically) effective, meaning that they helped participants lose up to 1.6 kg on average compared to a placebo. Others – supplements based on mangosteen, African mango, devil’s claw, and cissus – have shown promising results, but no more than three trials have been conducted for each, and not always using the proper methodology. As a result, researchers caution that these results should be treated with caution.
Separately, scientists analyzed the results of 67 clinical trials of dietary supplements in people with excess weight or clinical obesity. Dietary supplements based on chitosan, glucomannan, fructans and conjugated linoleic acid were tested. Chitosan helped the subjects lose an average of 1.84 kg, glucomannan (-1.27 kg) and acid (-1.08 kg) were both statistically but not clinically effective. “Herbal and dietary supplements may seem like a quick fix for weight problems, but people need to understand how little we know about them,” says Bessel. According to her, testing of dietary supplements is extremely rare, and almost nothing is known about their long-term effects. “The incredible growth of the industry and the popularity of these products make it important to conduct more extensive and thorough research in order to have reasonable confidence in their safety and efficacy,” she adds. Researchers present their work at the ongoing online European Congress on Obesity.