If you’re worried about high cholesterol or have already been diagnosed with it, you may be considering taking red yeast rice, a dietary supplement touted to lower cholesterol. Maybe you're even thinking about taking red yeast rice pills instead of your prescription cholesterol-lowering statin drug.

Red yeast rice supplements are popular: Americans spent some $49 million on them in 2015, according to Nutrition Business Journal. And a recent Consumer Reports investigation found them on the shelves of mainstream pharmacies and stores that sell supplements, including Costco, CVS, GNC, and Whole Foods.

“But taking these pills is not a good idea,” says Consumer Reports chief medical adviser Marvin M. Lipman, M.D.

Here’s what the research shows red yeast rice can do for your health—and the risks associated with taking it.

The Research

Red yeast rice is made by culturing rice with various strains of the yeast Monascus purpureus. And some studies have shown that certain red yeast rice supplements can lower LDL “bad” cholesterol.

For example, a 2015 review in the Journal Atherosclerosis, concluded that a daily dose of red yeast rice containing 10.4 mg of the active ingredient monacolin K, taken for at least four weeks, lowered LDL cholesterol more than a placebo, and was as effective as the prescription cholesterol-lowering drug lovastatin (Mevacor and generic).

That’s actually not all that surprising: monacolin K is chemically identical to lovastatin, says Pieter Cohen, M.D., an assistant professor at Harvard Medical School who studies dietary supplements.

Why, then, are these pills considered to be a dietary supplement and not a drug? Red yeast rice products were on the market before the Dietary Supplement Health and Education Act (DSHEA)—which loosely regulates supplements—was passed in 1994, Cohen says. “As with all other supplements on the market at that point, they were grandfathered in,” he says.

But that doesn’t mean red yeast rice supplements are safer than prescription statins. They aren’t. “Like statins, red yeast rice can cause exactly the same side effects as statins, and that includes muscle, liver, and kidney problems,” Lipman says. “And, even more important, red yeast rice supplements, like most supplements, aren’t standardized, so there’s no way to know the quantity or quality of the ingredients you are taking,” Lipman says. “That makes taking them even riskier.”

On the other hand, statin drugs, like all prescription medication, are carefully regulated by the Food and Drug Administration. They contain precise amounts of their active ingredient and must be taken under a doctor’s supervision. “When you take them, your physician monitors your kidney function and cholesterol levels on a regular basis, and can adjust the dose to prevent complications,” Lipman says.

Another problem: Red yeast supplements can contain citrinin—a chemical toxin linked to liver damage. There is no established safe level of citrinin, a compound that has not been well studied, Lipman says, “But consumers would be wise to avoid it.”

For all of those reasons, red yeast rice is one of the supplements on Consumer Reports list of 15 supplement ingredients that people should never take.

What to Do Instead

To lower your LDL, eat a heart-healthy diet that includes plenty of fiber from whole grains, fruit, vegetables, and beans—and limit your intake of saturated fat-laden red meats and full-fat dairy products. Losing excess weight, exercising regularly, and quitting smoking have all been shown to increase HDL, or “good” cholesterol, and have been associated with reduced risks of heart attack and stroke.

If you do need the power of a drug to lower your cholesterol, you are better off taking a prescription statin that is regulated by the Food and Drug Administration. That way, your doctor will be able to choose the correct medication for your condition. You will also know exactly how much of the active ingredient each pill contains, along with the risk factors and potential effects associated with it. For more information about statins, see our Consumer Reports Best Buy Drug report.

Taking prescription statins is also gentler on your wallet. A month’s worth of some generic statin drugs can cost as little as $4 at pharmacies like Kroger, Sam's Club, and Walmart, and statins are covered by most insurance plans, according to Consumer Reports Best Buy Drugs. Meanwhile 30 days worth of red yeast rice can cost about $13, and won't be covered by your insurance.