Next time you gulp down your favourite dietary supplement, or even take that concentrated green tea pill to burn fat, think twice. New data suggests that the unregulated dietary supplements industry accounts for nearly 20 per cent of drug-related liver injuries, up from 7 per cent a decade ago.

According to a new study, reported by New York Times, teenagers are not the only consumers at risk, many are middle-aged women who turn to dietary supplements that promise to burn fat or speed up weight loss. “When people buy these dietary supplements, it’s anybody’s guess as to what they’re getting,” Herbert L. Bonkovsky, director of the liver, digestive and metabolic disorders laboratory at Carolinas HealthCare System in Charlotte, NC, was quoted as saying. The supplement business is largely unregulated.

In recent years, said NYT, critics of the industry have called for measures that would force companies to prove that their products are safe and made in accordance with strict manufacturing standards before they reach the market.

The study found that many of the products implicated in liver injuries were bodybuilding supplements carrying unlisted steroids, and herbal pills and powders promising to increase energy and help consumers lose weight. The investigators looked at 845 patients with severe, drug-induced liver damage who were treated at hospitals from 2004 to 2012.

It focused only on cases where the investigators ruled out other causes and blamed a drug or a supplement with a high degree of certainty. One product that patients used frequently was green tea extract, which contains catechins, a group of potent antioxidants that reputedly increase metabolism. “Most green tea pills are highly concentrated, containing many times the amount of catechins found in a single cup of green tea, which can be toxic to the liver,” said Bonkovsky.

But liver injuries attributed to herbal supplements are more likely to be severe and result in liver transplants as these typically carry no information about side effects, said the report, quoting Victor Navarro, chairman of the Hepatology Division at Einstein Healthcare Network in Philadelphia. However, supplements like vitamins, minerals, probiotics and fish oil had not been linked to any adverse effect, the report added.