Monacolin, specifically monacolin K, is a naturally occurring compound found in red yeast rice (RYR), produced by the fermentation of rice with the mold Monascus purpureus. Monacolin K is chemically identical to lovastatin, a widely used prescription statin. Statins are well-established in clinical medicine for their cholesterol-lowering effects, primarily by inhibiting HMG-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis.

Numerous randomized controlled trials and meta-analyses have shown that red yeast rice preparations containing monacolin K can significantly lower LDL cholesterol, total cholesterol, and to a lesser extent, triglycerides. Since high cholesterol is a major risk factor for atherosclerosis (also known as arteriosclerosis), lowering cholesterol is accepted as a strategy to reduce the risk and progression of this condition. For example, a 2015 meta-analysis in the journal Atherosclerosis found that RYR significantly reduced LDL cholesterol in patients with mild to moderate hypercholesterolemia.

Regulatory bodies such as the European Food Safety Authority (EFSA) have acknowledged the cholesterol-lowering effect of monacolin K from RYR, allowing health claims for products delivering at least 10 mg/day. However, concerns exist about standardization, potential contamination, and side effects similar to pharmaceutical statins. Overall, the use of monacolin K for supporting the management of arteriosclerosis is supported by robust scientific evidence, primarily through its lipid-lowering action, which is a validated surrogate endpoint for cardiovascular risk reduction.