Red yeast rice
Monascus purpureus

In the European Union, a red yeast rice supplement may not provide 3 mg or more of monacolins per day. The limit has been in force since June 2022.

In the United States the framework is different. In 2015, the US national center for complementary health reported that the medicines agency considers products with more than trace amounts of monacolin K to be unapproved drugs. It is the most recent position we have been able to date.

This page describes the framework of Spain and the European Union. Anyone reading from another country is governed by the rules that apply to them. And it describes what published studies have measured, without making recommendations.

During fermentation the fungus produces a family of compounds, the monacolins. The main one is monacolin K, which is chemically and structurally identical to lovastatin, the first drug in the statin family to reach the market. It is not similar: it is the same molecule.

That is where its effect lies. Monacolin K inhibits the enzyme the liver needs to make cholesterol, and the liver compensates by pulling more cholesterol out of the blood. It is the mechanism of a statin.

The monacolins are a family. Besides K, others have been described, and the fermented product also contains sterols, isoflavones, monounsaturated fatty acids and the pigments that give it its color.

Monacolin K exists in two forms. A closed one, the lactone, which is inactive. An open one, the hydroxy acid, which is the one that inhibits the enzyme. The body converts the first into the second.

The content of monacolins other than K has been quantified in very few products. The European food safety agency states that the available data do not allow an assessment of what they contribute to the effect. The authors of the trial in statin-intolerant patients turn to them precisely to explain why their product lowered LDL more than its declared monacolin K content would suggest: they argue for an additive effect of the other thirteen monacolins present. That is a hypothesis of theirs, not a measured result.

It lowers LDL cholesterol. Trials with placebo find it and the meta-analyses that pool them confirm it, with a magnitude similar to that of one of the lower-potency statins.

A single trial has looked beyond the blood test to see whether those who take it have fewer heart attacks and live longer. It followed close to 5,000 Chinese people who had already had a heart attack for a mean of four and a half years, and found fewer coronary events and fewer deaths in the treated group. That result travels with some reservations: it was done only in a Chinese population, with the product of a single manufacturer, with an extract nobody fully characterized, and it is an old trial.

How much cholesterol drops in any one person depends on how much monacolin K the product they bought contains.

The second synthesis brought together fifteen high-quality trials, declares no conflicts of interest and is publicly funded. It finds that this equivalence with the statin is not uniform: they match on LDL and on HDL, the statin lowers total cholesterol more and red yeast rice lowers triglycerides more. It is worth knowing what that rests on. Of its fifteen trials, most compared against placebo; those that used a statin as the comparator, which are the only ones supporting that reading, are three at most, and two of them are not verified against their original source.

Neither synthesis can say which product produces which effect, because the trials they pool used preparations from different manufacturers with different monacolin K contents. Their own authors point this out.

The Chinese trial was called the China Coronary Secondary Prevention Study and used Xuezhikang, a partially purified extract that is not the product sold in Europe. All of its participants had already had a heart attack, so they started from a much higher risk than someone whose only abnormality is cholesterol. Its authors concluded that the product was safe and well tolerated.

The magnitude of the Chinese trial is what has been objected to most. The reduction in events and mortality it reports exceeds what statins of comparable potency achieve in Western secondary prevention trials. Three explanations have been proposed: an effect specific to the Chinese population, the contribution of other components of the extract, or limitations of generalizability and of reporting. None is established, and it is the main reason the trial is retained with reservations rather than treated as evidence transferable to a Western population.

There is also an unexplained inconsistency within the article itself. The abstract puts mean follow-up at four and a half years, while the table of lipid results heads it with three and a half years, and one of the meta-analyses coded the trial with this second figure.

A different limitation weighs on the two pooled syntheses: some of the trials they aggregate have not been verified against their original source by this team.

Adults with high cholesterol, or who want to lower it, and who are not already taking a drug to lower it. That is the population the trials were done in.

The trials were done in adults with high cholesterol who were not taking any drug to lower it. One recruited people who had stopped a statin because of muscle pain and agreed to try something else, and it is the best evidence available in that group.

Almost all lasted between six and twenty-four weeks. Apart from the Chinese trial of four and a half years, there are no data on what happens with prolonged use, either for efficacy or for safety.

The monacolin K doses in the trials that found an effect on LDL cholesterol range from 3 to about 10 mg per day. The limit European law allows a supplement is below 3 mg per day.

On time of day there is no data specific to red yeast rice. The rationale is carried over from statins, which are usually taken at night because the liver makes cholesterol mainly then, and the medicine’s prescribing information indicates taking it with the evening meal, since food increases its absorption.

None of this is a Suplepedia protocol.

The trials administered between 200 and 4,800 mg per day of the preparation, and that figure says little on its own: what counts is the monacolin K it contains, and two products with the same milligrams of red yeast rice can carry very different amounts. Treatments lasted between six and twenty-four weeks.

The European limit refers to the recommended daily dose on the package, not to the content of each capsule. And it falls on the monacolins, not on the red yeast rice: a product without monacolins is outside its scope, and also outside what the trials have measured.

The published doses are not directly comparable to one another. Some trials declare the milligrams of preparation, others those of monacolin K, and some give both figures without saying how they relate. The table records what each one declares, without homogenizing.

Since the European limit came into force, the market has shifted from pure red yeast rice toward blends with plant extracts or coenzyme Q10, which allow the commercial claim to be kept with fewer monacolins.

Monacolin K reaches the body in its inactive form and the body converts it into the active one. Before reaching the circulation it passes through the liver, where it is processed by the same enzyme system that metabolizes a good share of all medicines. Hence it interacts with so many of them, and curiously with grapefruit juice.

The lactone form works as a prodrug: it is inactive until the body opens it and converts it into the hydroxy acid. That conversion and the subsequent metabolism are handled by cytochrome P450 3A4, and the molecule is also a substrate of P-glycoprotein, the pump that returns substances to the intestine.

The passage through the liver retains most of what is ingested. The medicine’s prescribing information describes availability to the general circulation as low and variable, and puts at less than 5% the fraction of an oral dose that reaches it in active form, according to a single-dose study in four patients.

The practical consequence is that anything slowing cytochrome 3A4 increases the amount reaching the blood. That includes grapefruit juice, several antibiotics and antifungals and some antiretrovirals.

The question of whether the declared milligrams predict systemic exposure has two opposing primary answers. The only pharmacokinetic study in humans compared 2,400 mg of Chinese red yeast rice against 20 mg of lovastatin in eleven healthy volunteers and found higher peak concentrations and higher total exposure with the drug. A published commentary notes that this study may have been confounded by the concurrent administration of grapefruit juice. In the opposite direction, two later works describe the whole extract inhibiting cytochrome P450 and P-glycoprotein more effectively than the isolated monacolins, and producing greater exposure. The discrepancy remains open.

The variability does not begin with the product. The medicine’s own prescribing information puts at around 40% the between-subject coefficient of variation of the area under the curve for total inhibitory activity in the general circulation: the same dose of the same tablet produces different degrees of enzyme inhibition in different people.

On top of that, the ratio between the lactone and hydroxy acid forms varies between commercial products, and high batch-to-batch variability has been described within a single product.

No. Products with very different amounts of monacolin K are sold under the same name. In an analysis of 28 brands bought in US stores, in two none was detected, and among the rest the amount ingested per day following each package’s instructions varied more than 120-fold.

In Europe, an analysis of 37 products found that none met the pharmaceutical quality criterion requiring the actual content to be between 95% and 105% of the declared amount.

The effect and the risk depend on how much monacolin K the specific package contains, and that is what a label rarely lets you check.

None of those 28 US labels declared how much monacolin K the product contained. The figure appears in the full text of the study, not in its abstract, and we have not verified it.

The fungus that ferments the rice can also produce citrinin, a mycotoxin that is nephrotoxic in animal models, about which the European food safety agency declared it could not rule out concern over genotoxicity and carcinogenicity. European law sets a maximum of 100 µg per kilo of product. In the European analysis of 37 products citrinin was detected in all of them, in amounts from 100 to 25,100 µg per kilo, and only one met the limit. Four of those carrying it were sold labeled as citrinin-free.

That same analysis detected simvastatin, another prescription statin, in 30 of the 37 products, in amounts from 0.1 to 7.5 micrograms per daily dose. The authors do not claim it was added on purpose and offer no explanation. Their conclusion is that the market is under-regulated and under-controlled.

The actual content fell below the declared amount in nine products, with deviations of up to 83%, and above it in twenty-four, up to 266%. A later analysis of thirty-five products from the Belgian market found excessive monacolin K or serious bacterial contamination in four, and non-compliant European labeling in a little over a third of those bought through e-commerce, with the legal limit already in force.

The problem is not recent. In 2010, an analysis of twelve 600 mg US products found monacolin K between 0.1 and 10.1 mg per capsule and citrinin in four of them. In 2014, another found anomalous monacolin ratios against authentic reference samples.

There is also a coincidence worth stating carefully. The authors of the 2013 Belgian trial declared they could not rule out that the product tested had been artificially enriched, because without a natural reference ratio between monacolin K and the other monacolins there is no way to know whether all of it comes from fermentation. Eight years later, the Italian analysis detected simvastatin in thirty of thirty-seven products. Neither of the two articles claims that deliberate adulteration exists, and it is not claimed here either: the two findings are recorded, along with the fact that they point in the same direction.

It is worth recording where each thing comes from. A good part of the efficacy literature comes from extract manufacturers. The product quality studies are mostly academic or from government agencies.

We have not located, in scientific or regulatory sources, evidence that a red yeast rice product with active certification from a third-party verification program exists today. Everything known about actual content and contaminants comes from academic studies and from agencies, not from certification programs.

There is a useful contrast. The products used in some trials were characterized before being administered: accredited laboratory, monacolin K content measured, screening for citrinin and for heavy metals, documented batch. It is information that exists for a trial product and that whoever buys in a store does not have.

One of those products, from a 2020 Italian trial, went through an extract purification certification and showed no detectable levels of dehydromonacolins, decalin derivatives or contaminants. That trial was funded by Menarini IFR, the product’s manufacturer, which also supplied the active tablets and the placebo. Another, Belgian, went through an accredited laboratory that issued a numbered report, with screening for heavy metals, benzopyrene and citrinin. There the product was supplied by Decola Nutraceutics, which also collaborated in producing the placebo.

No one has compared two commercial products against each other in a trial. The variability documented by the market analyses has never been the subject of a clinical study, so it is not known what practical difference buying one or the other makes.

Nor is it clear that the milligrams on the label, even if accurate, predict how much reaches the blood. Two studies disagree on the direction of the effect, and the fermented matrix itself contains substances that interfere with the enzymes responsible for metabolizing monacolin K.

We have not located any trial on athletic performance. Nor any controlled trial on cognition: the only published study was done without a control group and its own authors describe small effect sizes across every dimension they measured.

Three open questions rest on hypotheses, not on data.

The first is the so-called phytocomplex effect: that the result is due to a synergy between the monacolins and the rest of the fermented matrix, and not to monacolin K alone. It remains in suspense because the direction of the pharmacokinetic effect is disputed between primary studies.

The second is why surveillance accumulates serious cases while the trials do not detect them. The argument has also been published that clinical trials are, by design, inadequate for defining a safety profile, a task that belongs to post-marketing surveillance.

The third is coenzyme Q10. Meta-analyses of comparable quality reach opposing conclusions, and the variable that separates them appears to be whether myalgia was confirmed before randomizing: those that confirm it tend to be negative.

European law requires the label of these products to carry five warnings. Four have prescribed wording: that it should not be consumed by anyone pregnant or breastfeeding, by children below 18 years old, or by adults above 70; that anyone experiencing any health problem should seek advice from a doctor on consumption of this product; that it should not be consumed by anyone already taking cholesterol-lowering medication; and that it should not be consumed together with other products containing red yeast rice. The fifth warns against reaching 3 mg of monacolins per day. The label must also state how many portions make up the maximum daily consumption and the monacolin content of each portion.

The warnings about cholesterol-lowering medication and about combining products have the same reason behind them: the effect adds up. Taking it while taking a statin, or taking two red yeast rice products at once, is raising the statin dose without anyone having calculated it.

It also shares the adverse effects of statins. The systems that collect reports from patients and doctors have accumulated cases of liver damage and of serious muscle damage, some with monacolin K doses as low as 3 mg per day. The placebo-controlled trials, which lasted a few months and did not include the people at highest risk, found no more liver or muscle problems than with placebo. Both things are true at once.

The placebo-controlled trials found no excess liver or muscle damage. A synthesis of thirteen of them puts the relative risk of adverse events at 1.18, with an interval between 0.91 and 1.54 that includes no difference. The authors of another synthesis warn that the quality with which those trials assessed safety was low.

The Italian surveillance system collected fifty-two reports between 2002 and 2015, corresponding to fifty-five adverse reactions. Thirteen required hospitalization, six of them for acute hepatitis. In seven cases the person took the product again and the reaction reappeared, which is the strongest indication of causality that exists here.

A 2026 paper tried to put a denominator on it: 148 reports in twelve European countries against an estimated exposure of 608,815 subject-periods, with no serious event classified as a certain or probable cause. It was done within a nutrivigilance framework operated by a consortium of manufacturers and its denominator comes from sales data. Spontaneous reporting always captures fewer cases than actually occur, so a rate calculated that way is a floor, not an incidence.

The information that follows comes from the prescribing information for lovastatin authorized by the US medicines agency, and is reproduced as context. It is not a Suplepedia protocol.

Potent inhibitors of cytochrome P450 3A4 raise concentrations and with them the risk of myopathy: itraconazole, ketoconazole, erythromycin, clarithromycin, telithromycin, HIV protease inhibitors and nefazodone.

On grapefruit juice, the prescribing information describes two studies of different sizes. In the first, ten people took 200 mL of double-strength juice three times a day for two days, and on the third day another 200 mL together with an 80 mg dose and again at thirty and at ninety minutes: exposure to lovastatin was multiplied fifteenfold and that of its active form fivefold. In the second, fifteen people took a glass of normal-strength juice with breakfast for three days, with a 40 mg dose on the third night, and exposure was multiplied by 1.94 and by 1.57. Those two figures are the counterparts of those from the first study, measured on the same molecules; the same summary gives another pair for the second study, 1.34 and 1.36, measured on inhibitory activity rather than on the molecules. And it notes that amounts intermediate between those two regimens have not been studied.

Gemfibrozil and other fibrates, niacin, cyclosporine, danazol, diltiazem, dronedarone, verapamil, amiodarone and ranolazine also increase the risk. With danazol, diltiazem, dronedarone or verapamil, the medicine’s prescribing information indicates starting at 10 mg and not exceeding 20 mg per day.

On anticoagulants, lovastatin can affect coagulation through displacement of protein binding with warfarin or acenocoumarol. The evidence is limited and rests on case reports.

The same prescribing information recommends checking liver enzymes before starting treatment and at any sign of liver damage. On the kidney it gives a specific figure: in severe renal impairment, with creatinine clearance between 10 and 30 mL/min, plasma concentrations after a single dose were approximately double those in healthy volunteers. Added to that, in the case of red yeast rice, is the risk of rhabdomyolysis with secondary kidney damage and the nephrotoxicity of citrinin.

The exclusion of adults over 70 imposed by the European label has a counterpart in the medicine’s prescribing information: in a study with sixteen patients aged 70 to 78 who received 80 mg per day, mean inhibitory activity in plasma was around 45% higher than in eighteen patients aged between 18 and 30.

On pregnancy and breastfeeding it is worth separating two things. One is the European regulatory exclusion, which is a fact. The other is that statins are classically contraindicated in pregnancy because of the role of cholesterol in fetal development, which is an extrapolation from the pharmacological class by chemical identity and not a datum observed with red yeast rice. The medicine’s prescribing information adds that, in animal studies, lovastatin crosses the placental barrier.

Before surgery or a blood test, and by the same analogy, consumption can raise transaminases and creatine phosphokinase and make those tests harder to interpret. We have not located a source specific to red yeast rice on this point.

A reference compendium on liver toxicity classifies red yeast rice as a probable but rare cause of clinically apparent liver damage, and attributes no case of acute liver failure to it.