Red yeast rice is a dietary supplement designed to help treat hyperlipidemia and heart disease. Americans spend about $20 million a year on the product, which contains the same statin (monacolin K) as prescription lovastatin.
Despite this, the supplement is regulated as a food, not a drug. But a new study published in the European Journal of Preventative Cardiology has shown that even after the FDA implemented good manufacturing practices, the amount of the active ingredient in red yeast rice can differ widely from brand to brand, even reaching prescription-strength levels.
The study looked at 28 different brands of the supplements, each on sold in at least one of four major chains—GNC, Walgreens, Walmart, and Whole Foods.
Two of the brands contained no monacolin K. The brands that did contain monacolin K varied widely—from 0.09 to 5.48 mg per 1200 mg of red yeast rice. Over one-third of the brands tested contained more than 2 mg of monacolin K per 1200 mg of red yeast rice. This means that consumers could be ingesting 0.09 to 10.94 mg of monacolin K per day, a difference of 120-fold. The study found that the dosages for some brands lined up with the dosages on prescription lovastatin tablets, which are produced in 10 mg, 20 mg, and 40 mg dosages.
No brand listed the amount of the monacolin K and only two brands warned the consumer not take the supplements with prescription statins. Previous studies have shown that consumers may suffer from the same adverse effects while taking red yeast rice as they would when taking a statin—effects possibly exacerbated when taken with another prescription statin.
So why all the variance? Red yeast rice is made by fermenting rice with different strains of Monascus spp., also known as ang-khak rice mold. As with any fermented product, minor differences in the process can lead to large differences in the final result. Authentic Chinese red yeast rice generally contains small amounts of monacolin K, but certain mutant strains of yeast can produce higher levels of the statin.
FDA regulations say that red yeast rice with higher levels of monacolin K—higher than 4 mg per day—are not supplements but unapproved drugs. Six brands tested in the study would qualify as unapproved drugs.
The study only tested one batch of each supplement, but the authors warn that even from batch to batch the amount of monacolin K is most likely variable. The study also only examined monacolin K, whereas red yeast rice can have multiple statin-like monacolins, potentially creating additional problems.