Wednesday June 4 2008
Red wine contains low levels of resveratrol
“Good health Shiraz a bonus” is the headline in The Sun today. Resveratrol, a compound found in the skin of red grapes, has been shown to block the “harmful effects of age in mice” the newspaper reports, suggesting that this may explain why the French have healthy hearts and arteries despite a high-fat diet. Other newspapers cover the story, including The Daily Telegraph, which reports that resveratrol inhibited genetic changes in the genes of heart and muscle cells that are associated with ageing.
The stories are based on a laboratory study in mice. The study did not investigate supplementing a high fat diet with resveratrol, so the claims that red wine stops the effects of a high-fat diet is a misinterpretation of the methods and results. There is a growing body of evidence from mice and invertebrates that resveratrol can have a positive effect on age-related processes. However studies are needed to determine whether these cellular changes occur in humans too, and whether these translate into benefits for heart function and lifespan.
Where did the story come from?
Dr Jamie Barger and colleagues from the University of Wisconsin, plus several other academic institutions across the United States, carried out this research. The study was funded by grants from the National Institute of Health and by DSM Nutritional Products. It was published in the peer-reviewed medical journal: PLoS ONE.
What kind of scientific study was this?
The study behind the stories is a laboratory study in mice. The researchers were interested in exploring whether resveratrol (a compound found in the skin of red grapes, red wine and other sources, such as pomegranates) can mimic the beneficial effects of calorie restriction on ageing. It is known that restricting calorie intake slows down several aspects of ageing and has beneficial effects in mammals. Resveratrol has been shown to extend lifespan, mimicking the effects of calorie restriction in some insects. However, studies in mice that were fed a high fat diet have been limited because of the toxicity of the diet, so the real effect of resveratrol in mammals has been difficult to determine.
The researchers divided their 14-month-old mice into three groups. The first group continued on the normal diet they had been eating (84 kcal/week); the second group had this diet supplemented with 5mg of resveratrol per kg per day; and the third group had a restricted calorie diet of 63 kcal/week. The number of spontaneous deaths in the three groups was recorded during this time, and when the mice were 30 months old they were sacrificed and their tissue samples collected. The researchers analysed the changes in the expression of genes known to be associated with ageing in heart, skeletal muscle and brain tissue samples and compared these between the different groups of mice. They also assessed cardiac function (heart rate, function of the valves, function of the muscle) and function of the skeletal muscle (use of glucose and insulin).
What were the results of the study?
Predictably, the researchers found that mice fed on a restricted calorie diet had reduced body weight compared with the control mice, although mice fed with resveratrol supplement did not show this same reduction in weight.
When they analysed the genes from the heart tissue of the mice, the researchers found that the low-calorie diet reduced by 90% the changes in gene expression known to be related to ageing compared with the mice on the control diet. The researchers also found that resveratrol prevented 92% of the age-related changes in gene expression in heart tissue compared with the control mice. The researchers found a less extreme effect of resveratrol on ageing skeletal muscles and the brain, with resveratrol supplementation leading to a reduction in 26% of age-related changes in gene expression in muscle, and 13% in brain tissue. This was similar to the reduction seen with the low-calorie diet. When they compared which genes were being affected, the researchers found that resveratrol mimicked the effects of calorie restriction (i.e. there was a large overlap in the genes affected) in all the tissues they examined. The researchers also found that resveratrol mimicked the effects of calorie restriction on heart function, i.e. there was improved age-related decline in the functioning of the heart, while circulating blood glucose was lowered.
The study was not set up to investigate the effects on lifespan as the mice were sacrificed at 30 months. The resveratrol did not reduce tumours in the mice and in particular, spontaneous liver tumours were abundant in the control mice and in those fed resveratrol but were rare in those on a calorie-restricted diet. The resveratrol did not reduce circulating levels of insulin-like growth factor (increased levels of which may increase the risk of cancer).
What interpretations did the researchers draw from these results?
The researchers say that a low dose of resveratrol can partially mimic the beneficial effects of calorie restriction and can improve quality of life by slowing down particular ageing parameters (such as cardiac dysfunction). However, they say that its use will need to be accompanied by a strategy to reduce insulin-like growth factor and its effects. They say that further studies should be carried out to test the relevance of these findings to humans.
What does the NHS Knowledge Service make of this study?
This animal study adds to a growing body of evidence suggesting that resveratrol can have beneficial effects on some aspects of ageing. Overall, the evidence for this comes from studies in mice and in invertebrates (yeast, worms and fruit flies). Human research is needed. This particular study did not investigate the effects of adding resveratrol to a high fat diet, therefore the newspapers’ claims that red wine stops the effects of a high fat diet is an overstatement; in addition, the mice were not given red wine per se. Importantly, red wine itself contains only a small amount of resveratrol, so relying on this as a source in not advisable and would need to be weighed against the negative and harmful effects of alcohol itself.
Sir Muir Gray adds...
A little alcohol does more good than harm; more than a little does more harm than good.