Monday June 15 2009
Scientists have said that people should sip wine to get the benefit of its “cancer-busting antioxidant”, the Daily Express reported. It said that the mouth absorbs 100 times more resveratrol than the stomach (resveratrol is a compound that attacks cancer cells and can protect the heart and brain from damage).
This news story is based on a review of recent research on the effects of resveratrol on health, disease and longevity. The newspaper reports the authors as saying that the mouth absorbs 100 times more resveratrol than the stomach. However, although this compound has shown benefits in animal experiments, the equivalent human doses “are well above those achievable... through a normal diet”. Research on fish, for example, achieved a 50% extension in the fish's lifespan, but a person would need to consume around 60 litres of red wine a day. Resveratrol has health improvement potential, but clearly more research in humans is needed.
Where did the story come from?
The research was carried out by Dr Lindsay Brown and colleagues from the University of Queensland in Brisbane, the University of Connecticut School of Medicine in the US, the University of Debrecen in Hungary and the University Hospital of Heidelberg at Manheim in Germany. The study was funded by the National Institutes of Health and the Dietmar Hopp Foundation. It was published in the medical journal Alcoholism: Clinical and Experimental Research.
What kind of scientific study was this?
This is a narrative review of recently published research on the potentially beneficial ingredients in red wine. The authors discuss how these ingredients, particularly polyphenols (chemical substances which include resveratrol), could work in the human body and their potential therapeutic uses.
Resveratrol is a type of compound known as a small polyphenol. It has been studied extensively in animals and insects and shown to extend the life of some yeasts, roundworms, fruit flies and obese mice that were given a high-calorie diet. It is thought to have similar effects to a low-calorie diet and that it may slow the ageing process.
The authors discuss recent evidence of the effects of resveratrol and put forward some theories about how it might have these effects. In particular, they discuss the apparent contradiction that while low doses improve the survival of some cells, providing a cardioprotective or neuroprotective effect, it kills cancer cells when given in high doses.
They discuss research into the potential benefits of resveratrol on cancer, inflammation, gastrointestinal diseases, neuroprotection, diabetes, heart health, blood pressure, blood vessels and cellular health, structure and function.
The researchers also discuss what is known about how the ingredients in red wine may benefit the body. They talk about the “bioavailability” of resveratrol and other polyphenols. Bioavailability is a property of a drug that describes how much of it enters the circulation and becomes “available” for the body to use.
What were the results of the study?
There are a number of different aspects to the researchers’ discussion into resveratrol. Some of the news reports of this research summarise them all, concluding that resveratrol has therapeutic potential. The Daily Express focused on the bioavailability of the compound.
What interpretations did the researchers draw from these results?
The researchers say that further research is needed to understand the role of resveratrol and other polyphenols, and how low-to-moderate amounts of red wine provide health benefits compared to white wine, beer or spirits.
They say that the known harms associated with alcohol consumption have prevented a fully controlled clinical trial of the effects of moderate consumption of red wine on cardiovascular disease risk.
What does the NHS Knowledge Service make of this study?
This narrative review discussed research on how resveratrol and other components of red wine may benefit health and how this might occur. Some news reports have focused on one aspect of the review: the bioavailability of resveratrol.
The researchers note that, so far, the positive observations in research have been made with doses of resveratrol “that are well above those achievable in humans through a normal diet”. They say that red wine is almost the only source of resveratrol in the human diet. To achieve an equivalent dose to the one that extended the lifespan of fish by 50%, a person would need to consume around 60 litres of red wine a day, which is certainly not feasible (or recommended!).
There is a growing body of evidence, largely from animal studies, that resveratrol can have a positive effect on health. The researchers emphasise that red wine contains only a small amount of resveratrol and a human would need to drink an unrealistically large quantity to have the same levels as those demonstrated in animal studies. Excessive alcohol consumption is associated with serious health risks and recommendations to drink in moderation should be taken seriously. If sipping wine prevents excessive alcohol intake then it should be encouraged, but human studies are needed to investigate the real health effects of red wine before it is recommended for health reasons.