Supplements, particularly herbal supplements, are generally seen as safe ways to potentially help our bodies and fight disease. But as a new study makes clear, not all supplements are safe, and consumers need to know that some can do serious damage.

As many as half of Americans use dietary supplements . A supplement may contain one ingredient or any combination of ingredients, such as vitamins, minerals, herbs, amino acids or some other lesser known substances. They are sold as tablets, capsules, liquids or powders.

Among the non-steroid supplements shown to cause harm were green tea extract, and concoctions labeled as “Chinese herbs,” “Korean herbs,” or “Ayurvedic medications.” Vitamins and other dietary supplements did not escape the list.

Anabolic steroids, synthetic versions of the male hormone, testosterone, are another type of supplement used by those who aspire to boost their athletic performance. They are illegal.

Researchers recently looked at liver injuries attributed to dietary and herbal supplements. They used data from the Drug Induced Liver Injury Network, a database set up by the National Institutes of Diabetes and Digestive and Kidney Diseases. Over 100 previously published studies were reviewed.

The review found that 20 percent of cases of chemical-induced liver damage were caused by herbal and dietary supplements, double that of a decade ago.

Anabolic steroids were the cause of over a third of the cases of liver damage, while the other cases were thought to be linked to 116 different products, many of which contained multiple ingredients, so it was hard to pinpoint the specific ingredient that could be responsible.

Among the non-steroid supplements shown to cause harm were green tea extract, and concoctions labeled as “Chinese herbs,” “Korean herbs,” or “Ayurvedic medications.” Vitamins and other dietary supplements did not escape the list. Certain products from manufacturers Slimquick, Herbalife, Hydroxycut, Move Free and Airborne were also found to harm the liver.

Liver damage from supplement use is rare, but when supplements are overused, taken in combination with other supplements or with prescription medications, or used for extended periods of time, the risk of harm goes up. Because people don’t always fully disclose all the products they are taking to their physician, problems with supplements may not be detected.

The problem with liver damage is that there may be no signs or symptoms until the damage is done; and without a functioning liver, you could not digest food, absorb nutrients or eliminate toxic substances. Without it, you would die.

There are plenty of prescription drugs that can cause liver damage, too, which is why many fail in development or end up being recalled. However, prescription drugs are used for a diagnosed medical condition and have proven benefits that are considered greater than the potential for liver damage when prescribed. Dietary supplements, on the other hand, have few or no proven benefits, but they do have proven risks.

When considering supplement use consumers would be smart to remember the old adage, “If it sounds too good to be true, it probably is.”

The study is published in the journal, Hepatology.