Dietary supplements have been at the center of a debate for years. Many medical experts question their value, but many natural health advocates and people who take them swear by their effectiveness and appeal as an alternative to Western style medicine that relies too often on pharmaceuticals to solve all health issues.

Without wading further into the debate, there should be no disagreement that anyone taking a dietary supplement should be ingesting what the label on the package claims is inside the bottle. Unfortunately, that is not always the case.

Last month, Pittsburgh-based GNC entered into an agreement with the New York Attorney General’s office to increase testing of products sold in its 6,500 stores across the country.

The motivation for GNC to settle came out of the attorney general’s examination of 78 bottles of popular supplements in which four out of five bottles were found to have no detectable DNA from the plants the product’s label claimed was inside the bottle.

The laboratory tests found that supplements frequently contained unlisted plants and other material or filler, including powdered rice, wheat, pine and even houseplants.

Investigators from New York’s attorney general’s office tested bottles of ginseng pills, which are marketed to promote overall health. Many of the supplements tested negative for any trace of DNA from ginseng plants.

Lack of oversight of the supplement industry makes these findings troubling — and not surprising. Experts long have warned that supplements are often tainted, containing unwanted filler material or even ingredients that could be harmful to people.

The American College of Medical Toxicology issued a statement on the issue, saying, “There is a lack of stringent quality control of ingredients present in many herbal and dietary supplements. Reliable evidence that these products are effective is often lacking...”

Congress appears to have done a huge favor for the supplement industry when it exempted supplements from the kind of standards or proof of effectiveness required by manufacturers of over-the-counter medications. Congress also allowed the supplement industry to avoid any federal regulation by the Food and Drug Administration.

There are steps Congress could take to correct the lax oversight of the $30 billion supplement industry. Topping the list would be requiring manufacturers to list ingredients and supply copies of labels. The industry should also list the ingredients and blends of ingredients that are contraindicated for subgroups of people, including children, pregnant women or people undergoing certain serious medical treatments. Another step would require suppplement makers to back up their claims of health benefits with solid scientific studies. Most of these ideas have been contained in legislation that was proposed, but did not advance in Congress.

The agreement between GNC and Eric Schneiderman, New York’s attorney general, is a step in the right direction — and Schneiderman wants to see it extend beyond GNC, noting he is urging Walgreens, Walmart, Target and others involved in the supplement industry to install quality control measures similar to what GNC plans. He also said he hoped manufacturers of herbal supplements would take steps to ensure purity of the ingredients and also make sure that actual contents match the description on the label.

The GNC settlement should revive efforts in Congress to impose more regulation, transparency and accountability on the supplement industry. At the very least, consumers should have assurances that when they take a dietary supplement they are getting what the label says is inside.