A variety of dietary supplements are marketed for improving cholesterol levels. Among the more popular ones include red yeast rice, flaxseed, and garlic. Is there sufficient evidence to say that these supplements are indeed effective in reducing cholesterol levels?
Thankfully, the National Center for Complementary and Alternative Medicine (NCCAM)has compiled past and emerging research about these supplements, and interestingly, these studies reveal mixed findings, as seen below.
Red yeast rice. Some red yeast rice products contain substances called monacolins, which are produced by the yeast. Monacolin K is chemically identical to the active ingredient in the cholesterol-lowering drug lovastatin, and can cause the same types of side effects and drug interactions as lovastatin. Other red yeast rice products contain little or no monacolin K, and it is not known whether these products have any effect on cholesterol levels. Unfortunately, there is no way to know how much monacolin K is present in most red yeast rice products. Further, the U.S. Food and Drug Administration has determined that red yeast rice products that contain more than trace amount of monacolin K cannot be sold legally as dietary supplements.
Flaxseed. Studies of flaxseed preparations to lower cholesterol levels report mixed results. A 2009 review of the scientific research of flaxseed for lowering cholesterol found modest improvements in cholesterol, seen more often in postmenopausal women and in people with high initial cholesterol concentrations.
Garlic. Some evidence indicates that taking garlic supplements can slightly lower blood cholesterol levels; however, an NCCAM-funded study on the safety and effectiveness of three garlic preparations (fresh garlic, dried powdered garlic tablets, and aged garlic extract tablets) for lowering blood cholesterol levels found no effect. Although garlic supplements appear to be safe for most adults, they can thin the blood in a manner similar to aspirin, so use caution if you are planning to have surgery or dental work. Garlic supplements have also been found to interfere with the effectiveness of saquinavir, a drug used to treat HIV infection.
From NCCAM.gov