Red yeast rice is sold as an herbal supplement in the United States. It has been known in China since the Tang Dynasty in 800 A.D. and is a dietary staple in many Asian countries. Red yeast rice contains the same chemicals, monacolins, as some prescription drugs designed to lower cholesterol. There is some evidence that red yeast rice may improve blood flow. Though most side effects are mild, there is evidence that red yeast rice causes muscle and kidney damage and may alter blood sugar levels.
Cholesterol-Lowering Effects
One of the most well-studied effects red yeast rice has on the body is its cholesterol-lowering properties. Red yeast rice contains chemicals called monacolins, which inhibit cholesterol synthesis. A specific monacolin, monacolin K, is the main ingredient in a well-known cholesterol-lowering prescription drug. Monacolin K is a strong inhibitor of HMG-CoA reductase, an enzyme responsible for synthesizing cholesterol in the body. Inhibiting HMG-CoA inhibits cholesterol production.
In addition to monacolin K, red yeast rice supplements may also contain isoflavonoids, monounsaturated fats and sterols that also work to reduce cholesterol and triglyceride levels even further. As a result, red yeast rice may improve circulation and/or increase blood flow.
Grapefruit has been known to increase the concentration of cholesterol-lowering drugs in the body, and therefore may also have an additive effect with red yeast rice.
Muscle Weakness
Red yeast rice may cause problems with muscle tissue in humans. Myopathy, muscle damage and weakness, has been reported in several instances of patients using red yeast rice.
In addition, in some rare cases, rhabdomyolysis has also been reported. Rhabdomyolysis is the breakdown of muscle fibers resulting in the release of muscle fiber contents, or myoglobin, into the bloodstream. These muscle fibers are harmful to the kidney and can cause kidney damage or liver damage, evidenced by dark urine, and/or yellowing of the skin or eyes.
Allergic Reactions
Red yeast rice has been reported to cause a rare allergic reaction in humans. There is one case report of a severe, anaphylactic allergic reaction in a butcher who touched meat containing red yeast, but no other reports were of note.
Miscellaneous Effects
A variety of mild side effects have been reported by people taking red yeast rice supplements. These effects are similar to those taking the prescription statin drugs designed to reduce cholesterol. These include mild headache, stomach pain, heartburn, gas, bloating, muscle pain, dizziness, asthma and kidney problems.
Effects on Pregnant and Nursing Women
The prescription drugs containing the active cholesterol-lowering ingredient found in red yeast rice has been classified as a Class X drug with respect to pregnant women. This means that studies in animals or humans have demonstrated fetal abnormalities and/or evidence of human fetal risk. In addition, studies have shown that monacolin K can pass through breast milk. Therefore, pregnant and nursing women are advised to avoid these drugs. Because red yeast rice contain the same ingredient, it's expected that red yeast rice would have the same effects and should also be avoided by pregnant and nursing women.
Blood Glucose Levels
Several reports on red yeast rice have stated that red yeast rice may lower blood glucose levels. This contradicts studies with the prescription drug containing Monacolin K that show no such effect. However, because the red yeast rice also contains other ingredients, and because the amount of the active ingredient in red yeast rice supplements can vary widely, it's recommended that people with diabetes check with their health care provider before using red yeast rice extract.
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