If you're looking to lose weight this year, do it the old-fashioned way - with a healthy diet and exercise - and stay away from herbal weight loss products and body-building formulas that new research has found to be linked to severe liver damage.

The New York Times is reporting on new research which found that dietary supplements account for nearly 20 percent of drug-related liver injuries - up from seven percent just 10 years ago. Some of these injuries were so severe they required liver transplants.

Many of the products implicated in these injuries were body-building supplements that contain unlisted steroids and herbal pills and powders such as green tea extract.

According to a blog entry on Fitness Edge, the new research was produced by the Drug-Induced Livery Injury Network which is part of the National Institutes of Health. The network consists of doctors at eight major hospitals throughout the country who are charged with the task of tracking patients who have suffered liver damage from certain drugs and alternatives.

In the latest study, investigators looked at 845 patients with severe, drug-induced liver damage who were treated at hospitals in the network from 2004 to 2012. When the network first began tracking these injuries in 2004, supplements accounted for seven percent of the 115 severe cases. That percentage leaped to 20 percent of the 313 cases studied from 2010 through 2012.

According to Dr. Navarro, an investigator with the network, the patients included dozens of young men who became ill after using bodybuilding supplements.

“They become very jaundiced for long periods of time,” he told the Times. “They itch really badly, to the point where they can’t sleep. They lose weight. They lose work. I had one patient who was jaundiced for six months.”

Tests revealed that a third of the products used by the men contained steroids that were not listed on their labels.

"A second trend emerged when Dr. Navarro and his colleagues studied 85 patients with liver injuries linked to herbal pills and powders," the Times reports. "Two-thirds were middle-aged women, on average 48 years old, who often used the supplements to lose weight or increase energy. Nearly a dozen of those patients required liver transplants, and three died."

One of the products used frequently by these victims was green tea extract, which contains catechins, a group of antioxidants that reputedly increase metabolism.

Marketed as fat burners, catechins are often added to weight-loss products and energy boosters, the Times reports. These pills are highly concentrated and contain many times the amount of catechins found in a single cup of green tea. What most people don't know, however, is that high doses of catechins can be toxic to the liver.

Dr. Navarro told the Times that liver injuries attributed to herbal supplements tend to be severe and to result in liver transplants.

Why aren't consumers being told about these dangers? Mostly because the supplement industry is unregulated, which leaves it susceptible to the unscrupulous.

Dr. Paul A. Offit, chief of infections diseases at the Children's Hospital of Philadelphia who is an expert on the supplement market, told the Times that an estimated 70 percent of dietary supplement companies are not following basic quality control standards that would help prevent adulteration of their products.

"Of about 55,000 supplements that are sold in the United States, only 170 — about 0.3 percent — have been studied closely enough to determine their common side effects," Dr. Offit said.

"When a product is regulated, you know the benefits and the risks and you can make an informed decision about whether or not to take it,” he said. “With supplements, you don’t have efficacy data and you don’t have safety data, so it’s just a black box.”

And it will remain this way until someone overturns the 1994 law known as the Dietary Supplement Health and Education Act which prevents the FDA from evaluating supplements before they are sold. As the Times report, the agency usually has to wait until after someone gets hurt before they can remove products from the shelf.

"Because the supplement industry operates on the honor system, studies show, the market has been flooded with products that are adulterated, mislabeled or packaged in dosages that have not been studied for safety," the Times reports.

This is why consumers need to heed the advice of Dr. Bonkovsky, an investigator in the network, who says consumers should not assume that supplements have been studied and tested because most of them have not.

“There is this belief that if something is natural, then it must be safe and it must be good,” he said.

This adage is nothing more than folklore. People who wish to use a dietary supplement for weight loss or muscle gain are asked to do so only under the supervision of their medical provider.

You can use this website to determine if the product you are using is known to cause liver damage.