There’s more to wine to surprise us

Resveratrol is a component of wine which has attracted much media attention. On 13th October 2006 the headline was “resveratrol in red wine could cut colorectal cancer risk”. Researchers from the Stoney Brook University in New York had examined the drinking habits of 360 moderate consumers of red and white wine and determined that red wine consumers had a 68 per cent reduced risk of colorectal cancer than white wine consumers. They declared that the major difference between the red and white wines was their content of resveratrol. On 24th September 2007 the headlines read “Secrets of a well aged red Australian - scientists are studying a chemical found naturally in red wine to see if it can extend the lifespan of human cells and help people live longer” and on 2nd November “Scientist uncorks secret to a long and healthy life-glasses of red wine- it may soon be possible to have your cake and eat it too, thanks to a substance in red wine with apparent anti-aging properties”. The gist of the article was that resveratrol shifts the physiology of middle aged mice on a high-calorie diet towards that of mice on a standard diet and significantly increases their survival. The implication is that perhaps resveratrol can be used to treat obesity-related disorders and diseases of aging in human. To put this latter paper into relevance, however, while these findings are in line with other animal data, the applicability to humans (both the safety and effects of long-term high doses of resveratrol) is not known.

What is resveratrol?

Resveratrol is the most studied of the many phenolic compounds found in grapes and wine over the past decade. It belongs to the stilbene phenolic class. It acts like an antibiotic and is produced by the skin cells of grape berries, and to a lesser extent the seeds and the leaves, in response to stress or pressure from fungal infections, and in response to injury. Correspondingly, a high concentration of resveratrol has been consistently measured in wines from cooler climate regions, such as Ontario in Canada, and Bordeaux and the Rhone Valley in France, which reflects a cool damp climate and increased fungal pressure. Conversely, a significantly lower concentration of resveratrol is generally measured in wines from relatively warm and dry climates, although some sub-regional differences are also observed.

What does resveratrol do?

Resveratrol has been reported to have both cardio-and cancer- protective effects in animal models and in humans. The cardio-protective effects of resveratrol include preventing blood clots from unnecessary forming and helping dissolve them when they do form, as well as helping arteries and veins to dilate to lower your blood pressure. High blood pressure increases your risk of cardiovascular disease. The cancer protective effects of resveratrol include preventing the initiation, promotion and progression of DNA damage and hence the formation of cancer cells by the repairing DNA damage in the pre-cancerous cells destroying the formed cancer cells. In addition, studies in worms, yeast and fruit flies, but not yet in humans, suggest that resveratrol can stabilise DNA repairs, and increase cell survival and hence the lifespan of these organisms by up to 70 per cent.

Conclusions

In conclusion, although the results of resveratrol studies are promising for human health, there are nine other classes of phenolic compounds with equally promising study results. There is also no definitive data on which class of phenolic compounds is the most efficacious for cardio and cancer protection. It is thus anticipated that the ten classes of phenolic compounds may act together in the human body, where the total concentration of phenolic compounds in wine may be more predictive of potential human health effects. Resveratrol content is thus not included on the label of wines or wine products

Creina S. Stockley, Health and Regulatory Information Manager, The Australian Wine Research Instute.