Monday June 9 2008
The red colour in Peking duck comes from red yeast rice
An “extract used in Chinese meals may be good for the heart”, The Daily Telegraph reports. The extract of Chinese red yeast rice, which “gives Peking duck its red colour”, was found to reduce the risk of dying from heart disease, or having another heart attack, in a study of almost 5,000 Chinese adults who had previously had a heart attack, the newspaper said. It adds that, “deaths from cancer were also reduced by two thirds”.
This large study showed that the extract had a beneficial effect. However, this is not surprising, as one of the original cholesterol-lowering drugs – lovastatin – was originally extracted from yeast rice. The findings about the effects of the extract on cancer deaths are not conclusive and need to be investigated further.
In addition to lovastatin, the extract contains other compounds, and the effects of these on humans have not been fully studied. For this reason – and because plant extracts are not as strictly regulated as medicines – anyone worried about their cardiovascular risk should consult their GP, who can advise them about whether they should start taking a statin, rather than red yeast rice extract. Also, they should not be mislead into believing that eating Chinese takeaways – many of which have a high fat content – will reduce their risk of heart disease.
Where did the story come from?
Dr Zongliang Lu and colleagues from the Chinese Coronary Secondary Prevention Study Group carried out this research. The study was funded by the Chinese National Scientific and Technological Projects and WBL Peking University Biotech Co. Ltd, the manufacturers of the extract used in the study. It was published in the peer-reviewed medical journal: American Journal of Cardiology.
What kind of scientific study was this?
This was a randomised placebo-controlled trial looking at the effects of Xuezhikang (XZK), an extract of red yeast rice, on heart health in people who had previously suffered a heart attack. This extract contains lovastatin, which is one of the statin drugs known to reduce “bad” cholesterol in the blood and reduce the risk of cardiovascular events.
The researchers enrolled 4,870 Chinese adults (3,986 men and 884 women, aged 70 years or younger) who had experienced a heart attack in the previous five years and been treated at one of 65 hospitals in China. Only people with average levels of low-density lipoprotein (LDL or “bad” cholesterol) in their blood were included. Those who had serious heart problems, high blood pressure, previous stroke, uncontrolled diabetes, liver or kidney disease, cancer, a history of alcohol or drug abuse, or women who might become pregnant, were not included in the study.
All participants ate a controlled diet for four weeks and were taken off any medications they were using to control their cholesterol. After this period, the level of cholesterol in their blood was measured, and they were randomly assigned to receive either two 300 mg XZK capsules (containing 5 to 6.4mg of lovastatin plus other compounds) or two inactive (placebo) capsules daily. The participants continued to take the tablets for an average of 4.5 years. They had check-ups six to eight weeks after the study started, and then every six months.
Researchers were mainly interested in major coronary events, such as non-fatal heart attacks or deaths from heart disease. They compared the proportion of people in the XZK group who experienced these events with the proportion in the placebo group. The researchers also looked at the levels of cholesterol in the blood, deaths from non-cardiac causes and any side effects of the treatment.
What were the results of the study?
During the study 139 people in the XZK group (5.7%) experienced major cardiovascular events, compared with 254 people in the placebo group (10.4%). This represented an absolute reduction of 4.7% in major events, or a relative reduction of 45% of events compared with the placebo.
When the researchers looked at cardiovascular mortality alone, they found that XZK reduced cardiovascular mortality by almost a third. XZK reduced “bad” cholesterol levels and increased “good” cholesterol levels. There were no serious side effects related to treatment and people in both groups experienced mild stomach upsets.
What interpretations did the researchers draw from these results?
The researchers concluded that long-term use of XZK reduced cardiovascular events in Chinese people who have previously had heart attacks.
What does the NHS Knowledge Service make of this study?
This study provides good evidence that the red rice extract XZK reduces “bad” cholesterol and subsequent cardiovascular events in Chinese people who have already experienced a heart attack. This finding is not surprising, as this extract contains lovastatin, a cholesterol-lowering compound that is already known to reduce cardiovascular risk. There are a few points to note when interpreting this study:
- It was unclear how the researchers identified what had happened to those people who did not attend their scheduled check-ups. It is possible that they missed people who had suffered cardiovascular events if they did not check hospital records.
- It was also unclear whether the researchers obtained independent verification of diagnoses of major cardiovascular events, or how they identified causes of death.
- As well as their main outcome – major cardiovascular events – the researchers also looked at a number of other outcomes. One of the findings, mentioned by the newspaper, is that deaths from cancer were reduced by two thirds. There are a number of reasons why this finding should be interpreted with caution: firstly, it is not known how these cancer deaths were identified and verified; secondly, cancer deaths were not the main focus of the paper and therefore the results can only be seen as preliminary; thirdly, as there were a number of outcomes tested, it is more likely that a statistical difference was found by chance. This finding will need to be confirmed by other studies looking specifically at this effect.
- As the authors of the study acknowledge, this extract contains compounds other than lovastatin that may contribute to its effects. These compounds “have not as yet been adequately isolated, analysed, and characterised for their consistency, stability, and individual pharmacologic and other properties and, therefore, require further study”.
People tend to think that substances extracted from plants must be better for us than “medicines”, and cannot be harmful. However, this is not the case. The contents of medicines such as statins are carefully tested and regulated, and they contain known concentrations of the active drug. Substances sold as health supplements are not so strictly regulated, therefore their contents may vary widely and cannot be guaranteed to be safe. For this reason, people who are concerned about their risk of heart attack or their cholesterol levels should talk to their GP, who may prescribe them a statin, rather than taking red rice extracts.
Sir Muir Gray adds...
The word "may" is the key word.