Red yeast rice — Natural doesn't mean safe

Some red yeast rice products have a substance called monacolin K. Monacolin K is like the active ingredient in lovastatin, a prescription medicine that lowers cholesterol. The amount of monacolin K in different brands of red rice yeast varies widely.

Products that have monacolin K can cause the same types of side effects as lovastatin. These may include damage to the muscles, kidneys and liver. In the United States, the Food and Drug Administration has ruled that dietary supplements that have more than trace amounts of monacolin K are not approved and can't be sold legally as dietary supplements.