Savvy Supplement Shopper is a blog by CSPI senior staff scientist David Schardt. This blog aims to parse the good from the bad from the truly awful in the supplement aisle.

If you’ve been thinking about buying a red yeast rice supplement to lower your cholesterol levels, you’ll need a lot of luck on your side. That’s because you won’t really know what you’re getting.

These supplements are produced by fermenting rice with various strains of a yeast that makes monacolin K, which is identical to lovastatin. That’s the active ingredient in the prescription statin drug Mevacor.

Red yeast rice with enough monacolin K in it can lower LDL cholesterol levels, but identifying a product that has enough is hit-or-miss, a new study confirms.

Researchers at Harvard University and the University of Mississippi recently bought 28 brands of red yeast rice from Walmart, Whole Foods, Walgreens, and GNC and measured how much monacolin K they contained.

Two brands didn’t contain any at all!

In the 26 that did contain at least some monacolin K, the amounts ranged more than 60-fold among brands! Some had barely any, some had a lot. Six of the brands, in fact, had more of the statin than what the Food and Drug Administration considers legal for a dietary supplement.

And consumers following the different dosages recommended on the labels could get 120 times more monacolin K from one product than from another. Not good.

Since none of the red yeast rice supplements were labeled with their amounts of monacolin K, consumers have no way of knowing whether they’re buying a potentially-effective product or a dud. (The researchers did not identify the brands they tested.)

Researchers at Harvard University and the University of Mississippi recently bought 28 brands of red yeast rice from Walmart, Whole Foods, Walgreens, and GNC and measured how much monacolin K they contained.

Two brands didn’t contain any at all!

Plus, we now know that red yeast rice can cause some of the same side effects as statin drugs, such as muscle pain in a small fraction of users. Yet only 2 of the 28 brands the researchers tested advised consumers not to take red yeast rice if they’re also on a prescription statin. Taking both would likely increase the chances of suffering side effects.

How much can red yeast rice lower cholesterol levels? A 2014 meta-analysis of 13 clinical trials in people with high cholesterol levels found that the supplement lowered total blood cholesterol by an average of about 38 mg/dl and LDL (“bad”) cholesterol by about 34 mg/dl. Of course, these studies probably were careful to make sure the red yeast rice they were using was potent.

Consumers, on the other hand, are on their own.

These new results showing that buying red yeast rice is a crap shoot are consistent with earlier studies by ConsumerLab.com, a supplement-testing company.

In addition, ConsumerLab found that the amount of monacolin K could fluctuate wildly from year to year even within the same brand. So even if you find one red yeast rice product that seems to lower your cholesterol levels, you won’t know if another batch of the same brand will do the same.

That’s a lot of uncertainty – some might call it gambling – when you’re trying to control a major risk factor for heart disease, the number one killer in the United States.

Companies are supposed to be following new quality-control regulations governing the manufacture of supplements so that this kind of mess doesn’t happen. Looks like the red yeast rice folks didn’t get the memo.

So, good luck buying a red yeast rice supplement. You’re going to need it.

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