Researchers have found wide variations in the amount of active compounds known as monacolins -- related to prescription drugs called statins -- in different brands of the popular dietary supplement red yeast rice.
Independent testing found that levels of total monacolins in 12 brands of red yeast rice ranged from 0.31 mg to 11.15 mg per capsule, according to Dr. Ram Y. Gordon, of the University of Pennsylvania in Philadelphia, and colleagues.
Therefore, "physicians should be cautious in recommending red yeast rice to their patients for the treatment of hyperlipidemia and primary and secondary prevention of cardiovascular disease," the authors warned in their Oct. 25 report in the Archives of Internal Medicine.
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Use of red yeast rice in the U.S. has skyrocketed in recent years, rising by 80 percent between 2005 and 2008. Long valued for its medicinal properties in China, it is produced by culturing the yeast Monascus purpureus on rice.
Studies of some formulations have suggested that consumption of red yeast rice can have beneficial effects on low-density lipoprotein (LDL) cholesterol -- with one trial finding decreases of more than 20 percent, according to the report.
"Our group has reported that red yeast rice, when combined with fish oil and lifestyle changes, is as effective as a moderate dose of simvastatin in lowering LDL-C levels," Gordon and colleagues wrote.
Because it is a dietary supplement and not regulated by the FDA, manufacturers generally do not provide detailed information about the levels of active ingredients in their products and are not permitted to make therapeutic claims for them.
In fact, the FDA has warned a number of red yeast rice manufacturers against making such claims or selling products containing high levels of lovastatin -- but many products remain easily available.
To determine the typical content of commercially available formulations, Gordon's group purchased 12 products which were analyzed for monacolin levels as well as for contamination with lead and the mycotoxin citrinin.
The analyses were done by the independent testing organization ConsumerLab.com.
None of the red yeast rice products tested were found to contain lead in excess of permissible levels, but potentially nephrotoxic citrinin was present in four products, in levels ranging from 24 parts per million to 189 parts per million.
The formulation that contained the highest levels of citrinin also had very low levels of both total monacolins (0.31 mg) and lovastatin (0.10 mg).
The average dose of lovastatin patients would receive if they took red yeast rice supplements as directed was 6 mg/day, and the maximum was 14.5 mg/day. The usual dose of pharmaceutical grade lovastatin (Mevacor) is 10 mg to 80 mg/day.
Recent trials of red yeast rice have found other cardiovascular benefits, including decreased rates of myocardial infarction and death from coronary artery disease.
These products also could be used safely in patients who developed muscle pain while taking statins or who prefer a natural product, the researchers noted.
An important limitation to this study, they acknowledged, was the possibility of variation in active ingredients between manufacturing batches and in bottles as purchased by the consumer.
Good manufacturing practices for dietary supplements, initiated during the past three years, may have lessened the likelihood of this, but each company can set its own standards and quality control measures.
The lack of standardization of active ingredients seen in this study is typical of alternative medicine products in general.
Variations in products can result from multiple factors, including growth and harvesting practices and the chemical complexity of many natural substances.
"Further oversight and standardization of the production and labeling of red yeast rice products may address some of the concerns raised in this study," the researchers suggested.