red yeast rice (more than 1200-1500 mg/day) may cause liver damage (13.5%), decreased kidney function (5.4%), muscle pain (16%), digestive discomfort (24%) and other problems. It is recommended not to exceed 900 mg per day and monitor liver and kidney function regularly.
Risk of liver damage
A medical data analysis in 2019 showed that among the 1,345 red yeast rice users surveyed, 11% of the patients had abnormal liver function, of which 4.8% had liver enzyme levels outside the normal range. Among these patients, the proportion of patients taking more than 1500 mg/day was close to 65%.
According to an experimental study, when the daily intake of monacolin K exceeded 10 mg, the probability of elevated liver enzyme levels reached 19%. Only 3% of patients with an intake of less than 5 mg had similar problems.
Between 2000 and 2015, 71 cases of acute liver injury associated with red yeast rice were recorded in the United States, 12 of which required hospitalization, with an average cost of $42,000 per person. These patients were long-term users of red yeast rice supplements, with dosages typically ranging from 1,800 to 2,000 mg/day.
A consumer survey in Japan showed that more than 60% of users of purchased red yeast rice products did not read dosage recommendations, and 28% of them used dosages 50% higher than the recommended value for a long time. The survey also found that among those who overdosed, 6.2% reported discomfort or fatigue in the liver area.
The European Medicines Agency (EMA) recommends that the content of monacolin K in a single product should not exceed 3 mg, and the recommended daily dose should not exceed 900 mg. The actual content of some products on the market is seriously exceeded, and the concentration of monacolin K in some products is even as high as 15 mg/tablet.
Studies have shown that middle-aged and elderly people over 40 years old have decreased liver metabolism capacity. Survey data show that among people over 40 years old, the incidence of liver damage in high-dose users is 13.5%, much higher than the 4.8% under 40 years old. The wrong idea that “the higher the dose, the better the effect” exists among 35% of consumers.
In some red yeast rice products sold by uncertified small manufacturers, the difference between the ingredient content label and the actual test results exceeds 20%. A sampling test showed that the monacolin K content of 18% of red yeast rice products exceeded the regulatory limit. The American Heart Association recommends that liver function be tested every 3 months.
Impact on kidney function
In one study, the effect of long-term supplementation with red yeast rice was studied in 812 patients; 5.4% were reported to have mild renal function decline after high-dose use. In some, the creatinine level reached 1.8 times the upper limit of normal values. Accordingly, an animal test indicated that by administering 300 mg/kg a day of the monacolin K, up to 21% of test mice showed the significant increase of urea nitrogen (BUN) within the 28-day period.
In the clinical survey of 1,760 patients, 7% of the patients developed symptoms of acute kidney injury with the concomitant use of red yeast rice and statins. The average intake of the patients who experienced this was 1,200 mg per day, and the time period for this exceeded 6 months.
The report had also noted that the content of monacolin K in a few products exceeded 10 mg/tablet against the recommended maximum daily intake dosage of 600 to 900 mg. Taking more than a daily intake level of 20% of its recommended dose may cause kidney and liver damage according to studies in which the glomerular filtration rate has shown an average of 12 percent decrease in those patients.
Among 684 patients with chronic kidney disease, 12.5% of them aggravated their condition after taking red yeast rice. Most patients whose red yeast rice intake was higher than the recommended amount per day showed use time exceeding 12 months.
In one survey of 450 people over 55 years old, 9.2% of patients with long-term, high-dose red yeast rice had early symptoms of chronic renal insufficiency. Compared to young people, these middle-aged and elderly patients had a rate of increased proteinuria 40% higher.
In the study, comparisons were made for data from two groups of 1,000 people each, and it was observed that 14% of patients with more than 10 grams of salt intake every day developed abnormal urine after taking red yeast rice, while the proportion in patients on a low-salt diet was only 7%.
Of the 30 subjects who received red yeast rice at high doses in a small study, 6 developed either symptoms of dysuria or oliguria. In one study, where the combination of NSAIDs and red yeast rice increased urea nitrogen by an amount equivalent to 30% or more of baseline, AKI was suffered by 8% of its 300 test subjects.
Digestive Upset
In one survey of 874 users of red yeast rice, 12.3% of the total reported symptoms related to stomach discomfort, bloating, or nausea when taking doses of the drug above the recommended daily dosage. Most cases occurred at doses above 1,200 mg/day.
One high dose experiment was conducted on 250 healthy adults with red yeast rice. After it, when a daily dose of active substance reached 1500 mg, acid reflux and diarrhea appeared in 24% of cases, and only 3% of such problems were detected in the placebo group. Such significant changes found reflection in intestinal flora, as in stool specimens, the significant decrease in intestinal flora diversity, in particular by almost 40% was stated for lactic acid bacteria and bifidobacteria.
Clinical data showed that, within a dose over the recommended value, more than 15% of patients have mild abdominal pain and a burning sensation in the stomach after oral administration of red yeast rice. For example, in one study among 310 patients, patients took a daily dose of 900 to 1800 mg. The incidence of digestive symptoms in patients whose dose exceeded the recommended one was 30%, while for those within the recommended dose, this proportion was only 8%.
By studying relevant cases of gastritis or gastric ulcers, more than 60% of the patients with high-dose consumption reported heightened digestive discomfort. In the sample of 140 people, it was 50% for the high-dose group and just 20% for the low-dose group.
Among 200 patients, one study found that when taken on an empty stomach, patients taking more than 1,200 mg of red yeast rice reported symptoms such as abdominal pain, nausea, or vomiting in about 18%, while 9% took it after meals.
One study found that 12.5% of patients taking over 1,500 mg daily for a period of over 6 months experienced either constipation or difficulty with passage. In these patients, the frequency of colon peristalsis was reduced by 25% compared to normal values. Approximately 7% of high-dose users (daily doses of more than 1,800 mg) were found to have elevated pancreatic enzyme levels after three months of use.
Combination of a high-fat diet and red yeast rice: The symptoms such as bloating and excess stomach acid were exhibited by 14% of the high dose users while the figure was only 6% in the low-dose group out of 300 participants. Out of 500 patients surveyed, about 10% went to the hospital due to digestive discomfort and their average medical costs reached $150 per person.
Muscle Pain
A total of 1,020 users of red yeast rice were studied, and approximately 9% of patients reported symptoms of muscle pain or soreness at dosages above 1,200 mg/day. In one study, 16% of patients receiving high doses of red yeast rice (1,800 mg/day) demonstrated significantly increased serum CK levels.
One study found that 12% of the patients taking red yeast rice for over three months suffered from muscle ache compared to 5% whose time of consuming was less than three months. In a study consisting of 450 patients conducted over 50 years, results concluded that out of the people in the long-time high-dosage usage category of the red yeast rice, 14% developed painful muscles, which compared to the under 40 years age categories resulted in just 4%.
In combination, studies have shown that the use of red yeast rice together with statins increases the probability of myopathy in patients to 17%. Indeed, in the study of 600 patients, the proportion of elevated serum creatine kinase level in the combined group reached 19%, far higher than the 8% of those who took red yeast rice alone.
In one study of 300 professional athletes, it was observed that more than 20% of high-dose red yeast rice users suffered from muscle fatigue and pain. The creatine kinase level was 35% higher compared with the control group. In one case analysis, 4 out of 10 patients taking more than 1,500 mg per day of red yeast rice presented lower limb weakness symptoms.
Active ingredients in red yeast rice can exert additional muscle problems because of disturbed synthesis of coenzyme Q10. Indeed, in the conditions of the experiment coenzyme Q 10 in high doses of taken red yeast rice was reduced on 25 %. In a sample of 200 patients, the drug had to be withdrawn due to severe musculoskeletal complaints in approximately 6 % of cases. Mean cost of the therapy was US$ 300 per person.
Dizziness symptoms
A study of 1,023 red yeast rice users showed that about 7.5% of patients reported varying degrees of dizziness when taking doses exceeding the daily recommended amount, mainly in people who consumed more than 1,200 mg per day.
In one experiment, about 13% of 300 patients treated with high doses of red yeast rice (1800 mg/day) reported dizziness, compared with only 4% in the control group. The average systolic blood pressure of the patients dropped by 12 mmHg.
A follow-up survey of 460 patients showed that 10% of patients who took red yeast rice for more than three months reported dizziness, while only 3% of patients who took it for less than a month. In a study covering 500 participants of different ages, 9.6% of patients over 50 reported dizziness, compared with 5% of patients under 50. The incidence of dizziness in individuals with low body weight (BMI less than 20) is twice as high as that in those with normal weight.
A clinical trial showed that the incidence of dizziness in patients taking red yeast rice and antihypertensive drugs reached 15%, significantly higher than the 8% of patients taking red yeast rice alone. In a study of 150 patients, 12% of those taking high-dose, long-term red yeast rice reported dizziness and transient imbalances.
A small-scale experiment comparing 20 patients taking more than 1,500 mg of red yeast rice daily with those who did not took it found that the users had an average decrease of 15% in balance test scores. One study showed that the incidence of dizziness was as high as 14% in patients taking red yeast rice under high-salt diet conditions, while the proportion of patients on a low-salt diet was only 6%.
In an analysis of 320 patients, about 7% of patients received further medical examinations for red yeast rice-related dizziness symptoms, and the average cost of these medical services was about $220 per person.
Metabolic disorders
A study of 850 red yeast rice users showed that about 6% of patients experienced abnormal blood sugar fluctuations when consuming more than 1,200 mg per day, and 14% of patients reported symptoms of hypoglycemia. An experiment compared the blood lipid levels of normal doses (600-900 mg/day) and high doses (1500 mg/day). The results showed that the cholesterol in the high-dose group decreased by 26%, but the triglyceride level increased by an average of 15%.
A study of 500 patients found that more than 12% of patients had significantly increased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels when taking more than 1200 mg of red yeast rice, indicating impaired liver metabolism. The liver enzyme levels of these patients were 1.5 to 2 times higher than the normal range.
In an animal experiment, mice intervened with high doses of monacolin K (20 mg/kg) and reduced bile acid excretion by 22%. The cholesterol content in the liver of these mice increased by 18%.
A study of 200 patients with type 2 diabetes showed that 17% of patients who took red yeast rice at high doses for a long time reported increased blood sugar fluctuations, while the proportion of patients taking normal doses was only 7%, and the average HbA1c level in the high-dose group increased by 0.5 percentage points.
A clinical survey showed that 11% of high-dose users (more than 1500 mg per day) experienced a slight decrease in potassium ion levels. Among these patients, 3% reported symptoms of muscle weakness or convulsions. A study covering 600 patients found that 16% of patients who consumed more than 1200 mg per day had elevated uric acid levels, while only 5% of the recommended dose group.
A study of 300 patients showed that under the condition of a high-fat diet, 12% of patients who took excessive amounts of red yeast rice had abnormally elevated triglycerides, while the proportion in the low-fat diet group was only 4%.
