Hong qu (红曲, red yeast rice; ang kak in Hokkien, beni-koji in Japanese) is cooked rice fermented with a mould, usually Monascus purpureus, until each grain turns deep red. Ground into powder or used to brew red rice wine, it has long coloured and flavoured southern Chinese food – the red of some char siu and red-braised pork, Fujian red rice wine and its lees, and Okinawan tofuyo, tofu aged in a red mould-rice and awamori paste. Despite the English name, it’s made by a mould, not a yeast.
Why Red Yeast Rice Contains a Statin
Monascus can make monacolins. In 1979, the Japanese biochemist Akira Endo described monacolin K, a cholesterol-lowering compound produced by a Monascus species (Endo, 1979); in its lactone form it is identical to the prescription statin lovastatin (EFSA, 2018). That’s why red yeast rice became a cholesterol supplement. In a 12-week trial, 83 adults with high cholesterol taking 2.4 g a day of a red yeast rice product saw total and LDL cholesterol fall compared with placebo (Heber et al., 1999), and a meta-analysis of 20 trials found an LDL reduction of about 1 mmol/L, similar to statins – while warning that most trials assessed safety poorly (Gerards et al., 2015).
The Safety Problems
- It acts like a drug. The European Food Safety Authority found that monacolins from red yeast rice supplements can reach the range of therapeutic lovastatin doses, that they were of significant safety concern at 10 mg a day, and that severe reactions – including muscle breakdown (rhabdomyolysis) and liver injury – had been reported at intakes as low as 3 mg a day (EFSA, 2018). The EU now limits supplements to less than 3 mg of monacolins per daily portion and requires warnings (Regulation (EU) 2022/860). The same drug interactions and side effects as statins apply.
- Citrinin. Monascus can also produce citrinin, a mycotoxin that damages the kidneys in animal studies (EFSA CONTAM Panel, 2012). Producers control it with selected strains, controlled conditions and testing.
- Contamination. In 2023–24, red yeast rice (beni-koji) supplement tablets in Japan were linked to kidney injury in a nationwide survey of 192 patients, many with Fanconi syndrome; most still had reduced kidney function at follow-up (Shinzawa et al., 2025). The strains involved made no citrinin; investigators found puberulic acid and other unintended compounds traced to contamination with a Penicillium mould at the manufacturing site (Tanaka et al., 2025).
Why There’s No Home Recipe Here
Growing Monascus on rice is easy to describe, but the risks above depend on things you can’t check in a kitchen: which strain you have, how much citrinin and monacolin it made, and whether another mould got in. The Japanese outbreak happened in a factory. So we don’t give a home method. If you want hong qu for cooking, buy food-grade red yeast rice powder, grains or red rice wine from a reputable supplier, and use it the traditional way – a teaspoon or two to colour a marinade or braise.
Who Should Avoid It
Don’t use red yeast rice products to treat high cholesterol without your doctor, and don’t combine them with a statin. People who are pregnant or breastfeeding, children and older adults are among the groups the EU singles out for warnings (Regulation (EU) 2022/860). For other mould-fermented foods that are safe to make with bought spores, see our guides to miso and tempeh, or season with koji in shio koji.