red yeast rice

Red yeast rice is produced by fermenting a fungus (usually Monascus purpureus) on rice. The fermentation can enrich the rice with compounds called monacolins, the most notable of which is monacolin K. NCCIH notes that monacolin K is structurally identical to the prescription cholesterol drug lovastatin. The amount of monacolin K varies widely from product to product, and because levels are not usually listed on labels, a consumer generally cannot tell how much any given product contains.

According to NCCIH, red yeast rice products that contain substantial monacolin K may lower blood cholesterol (and possibly blood glucose and blood pressure) — but this is because monacolin K is the same compound as the drug lovastatin. The FDA considers products containing substantial monacolin K to be unapproved new drugs that cannot be legally sold as supplements in the United States. NCCIH notes that products with little or no monacolin K may have little or no effect on cholesterol. Because the monacolin K content is usually not shown on labels — a 2017 review found that monacolin K levels across tested brands ranged more than 60-fold (about 0.09 to 5.48 mg per 1,200 mg) and that none of the products listed the amount on the label — the actual effect of any specific product is unpredictable.

There is no established or reliable dose. NCCIH stresses that consumers usually cannot know how much active monacolin K is in a given product, and that products with substantial monacolin K cannot be legally sold as supplements, so effectiveness is unpredictable. Do not self-treat high cholesterol with red yeast rice; talk to your doctor or pharmacist before using it, especially if you take any medications or already use a statin.

NCCIH reports that the evidence on safety is mixed: a 2019 review suggested red yeast rice products were generally safe, while the European Food Safety Authority concluded in 2018 that monacolin K exposure could lead to severe side effects and that it could not identify a guaranteed safe intake level. A notable concern is contamination with citrinin, a toxin that can damage the kidneys; in a 2021 analysis of 37 products, only one had citrinin levels below the European limit, and four products labeled "citrinin-free" were still contaminated. NCCIH states there are no studies on the safety of red yeast rice during pregnancy or breastfeeding, and these products are not recommended for people who are pregnant or lactating.

Because products containing monacolin K act like the statin lovastatin, NCCIH says they can carry the same potential side effects as statin drugs. These include damage to the muscles, kidneys, and liver, along with digestive complaints such as diarrhea, nausea, and stomach pain.

As a lovastatin-equivalent, red yeast rice can have the same types of drug interactions as statin medications, so it may interfere with certain medicines or raise the chance of side effects. NCCIH advises caution about combining it with statin drugs or other medications without medical guidance; talk to a clinician or pharmacist about possible interactions before use.