Red yeast rice is the product of yeast (Monascus purpureus) grown on white rice. The powdered yeast-rice mixture is a dietary staple in Asia and has been used in traditional Chinese medicine.

Red yeast rice is also available as an oral supplement.

Red yeast rice might contain compounds that appear to lower cholesterol levels. One of the compounds is monacolin K, the same ingredient that is in the prescription cholesterol-lowering drug lovastatin (Altoprev).

As an oral supplement, people take red yeast rice for high cholesterol and heart disease.

Research on red yeast rice use for specific conditions shows:

• High cholesterol (hyperlipidemia). Research shows that red yeast rice containing considerable amounts of monacolin K can lower your total blood cholesterol level, your low-density lipoprotein (LDL, or "bad") cholesterol level and your triglyceride level.

Red yeast rice can cause mild side effects, including:

• Abdominal discomfort
• Heartburn
• Gas
• Headache
• Dizziness

Red yeast rice might contain monacolin K, the same ingredient that is in the prescription cholesterol-lowering drug lovastatin. Lovastatin side effects include liver damage and muscle disorders (myopathy).

Don't take red yeast rice if you're pregnant, trying to become pregnant or breast-feeding.

An older study raised the concern that some red yeast rice products contain a contaminant called citrinin, which can cause kidney failure. However, a more recent study that analyzed 14 red yeast rice dietary supplements didn't find citrinin in any of them.

Possible interactions include:

• Alcohol. Don't drink alcohol if you are taking red yeast rice. The combination might increase the risk of liver damage.
• Cyclosporine (Neoral, Sandimmune). Taking this immunosuppressive drug with red yeast rice might increase the risk of myopathy.
• Cytochrome P450 3A4 (CYP3A4) inhibitors. Taking red yeast rice with drugs, such as erythromycin, that inhibit this enzyme might increase the risk of harmful red yeast rice side effects.
• Grapefruit. Drinking grapefruit juice and taking red yeast rice might increase the risk of the supplement's harmful side effects.
• Gemfibrozil (Lopid). Taking this cholesterol drug with red yeast rice might increase the risk of myopathy.
• Hepatotoxic drugs, herbs and supplements. Red yeast rice might contain monacolin K, which can cause liver damage in some people. Taking red yeast rice with these types of drugs, herbs and supplements could increase the risk of liver damage.
• Niacin. Taking red yeast rice with high-dose niacin might increase the risk of myopathy.
• St. John's wort. Taking this supplement with red yeast rice might reduce the effectiveness of red yeast rice.
• Statin. Taking red yeast rice with other statins might increase the risk of harmful side effects.