context: Red yeast rice extract ( RYRE) is a traditional Chinese medicine that has been purported to lower cholesterol. Several types of the extract are sold as supplements. Red yeast rice may be appealing because it's "natural," but you need to be careful. Experts have not studied it extensively. The ideal dosing and its long-term safety are unclear. It could be dangerous for some people. And because the ingredients of different brands of red yeast rice extract might vary so much, it's hard to make firm statements about its effectiveness or safety. RYRE is a substance that's extracted from rice that's been fermented with a type of yeast called Monascus purpureus. It's been used in China and other Asian countries for centuries as a traditional medicine. It's also used as a food coloring, additive, and preservative. RYRE naturally contains several ingredients that may help control cholesterol levels. These include a number of monacolins, most importantly monacolin K. It also contains sterols, isoflavones, and monounsaturated fatty acids, or "healthy fats." Confusingly, the answer is both. One of the most important ingredients in RYRE is monacolin K. It's also known as lovastatin, the active ingredient in the prescription drug Mevacor. So on one hand, the extract is a traditional remedy that helps lower cholesterol. On the other, the pharmaceutical manufacturer of Mevacor argues that it owns the rights to the ingredient lovastatin. This confusion extends to how the supplement is sold in the U. S. Because red yeast rice extract contains a substance classified as a prescription drug, the FDA has requested that several RYRE products be withdrawn from the market because they contained lovastatin. The FDA cited a risk of severe muscle problems that could lead to kidney disease. Despite the FDA's attempts, many people in the U. S. still manage to get similar red yeast rice extracts from other countries or on the Internet. Studies have shown that certain red yeast rice products that contain statin can significantly lower levels of total cholesterol and specifically LDL, or "bad" cholesterol. One showed that taking 2.4 grams per day reduced LDL levels by 22% and total cholesterol by 16% in 12 weeks. Another study showed that taking 1.2 grams per day lowered LDL levels by 26% in just eight weeks. However, the results of these studies depend on the amount of statin that is in the extract, and it can vary widely. The FDA considers extracts that contain statins to be illegal in the U. S., but many are still available. Keep in mind that the amount of monacolin -- perhaps the most important ingredient -- in a red yeast rice extract can vary a lot. There are many different strains of the yeast. Different types of fermentation are used. One study of different brands of red yeast rice supplements showed that the amount of monacolin ranged from 0% to 0.58%. So even though studies have shown that RYRE can lower cholesterol, you can't really know if the supplement brand you're using will have that effect. Studies have shown that side effects are mild, like headaches, heartburn, and upset stomach. Side effects from prescription lovastatin include elevation of liver enzymes and muscle enzymes, muscle problems, and liver problems. But more research needs to be done before we can know about the long-term safety of red yeast rice extract. We do know that some types may be more dangerous than others because of high levels of other substances such as citrinic acid. RYRE also shares some of the same risks as statins, the class of drugs containing lovastatin. Experts say that the risks of lovastatin would logically apply to RYRE -- elevation of liver and muscle enzymes, muscle problems, and liver problems. The extract may not be safe for everyone. You should not take it if you: Have kidney disease Have liver disease Are pregnant Are breastfeeding In addition, anyone taking one of the following medicines should not use red yeast rice: Statins to control cholesterol such as lovastatin ( Mevacor), rosuvastatin ( Crestor), fluvastatin ( Lescol), atorvastatin ( Lipitor), pravastatin ( Pravachol), and simvastatin ( Zocor) Other cholesterol drugs such as gemfibrozil ( Lopid) and fenofibrate ( Tri Cor) Drugs to suppress the immune system, like cyclosporine Antifungal drugs such as fluconazole ( Diflucan), ketoconazole ( Nizoral), and itraconazole ( Sporanox) The antibiotics erythromycin and clarithromycin ( Biaxin) Serzone, an antidepressant Protease inhibitors, used to treat HIV People who have allergies to fungus or yeast should also be wary of using RYRE. The extract may also interact with other drugs for blood pressure and thyroid problems and interact with other herbs and supplements you may be taking. Whatever the state of your health, always talk to your doctor before you start using red yeast rice or any other supplement. Remember that not all brands are equal, and that RYRE isn't safe for everyone. Though red yeast rice extract looks like a promising treatment, more research needs to be done. For now, you should be cautious.