Resveratrol, a compound found in grapes, red wine and peanuts, can improve blood flow in the brain by 30 per cent, thereby reducing the risk of stroke, according to the results of a rat study.

Researchers at the National Taiwan Normal University and the National Chia-Yi University report that rats with induced reduction of blood flow (ischemia) in the brain experienced an improved blood flow from a single dose of resveratrol.

“We found that resveratrol administration… led to cerebral blood flow elevation and protected animals from ischemia-induced neuron loss,” said lead author Kwok Tung Lu.

Strokes occur when blood clots or an artery bursts in the brain and interrupts the blood supply to a part of the brain. It is the leading cause of disability and the third leading cause of death in Europe and the US. According to the Stroke Alliance for Europe (SAFE), about 575,000 deaths are stroke related in Europe every year. In the US, every 45 seconds someone will experience a stroke, according to the American Stroke Association.

The new study, published in the Journal of Agricultural and Food Chemistry (Vol. 54, pp. 3126-3131), divided 60 adult male Wistar rats into three equal groups. The first group was the control. The second group underwent the induction of cerebral ischemia, and the third group underwent the same operation but also received an intravenous dose of resveratrol (20 milligrams per kilogram body weight).

Although no change to mean blood pressure or heart rate was observed, cerebral blood flow in the second group decreased by 65 per cent compared to the control group. The ischemia plus resveratrol group’s blood flow also decreased, but by only 35 per cent.

The researchers also found that the concentration of nitric oxide (NO) in the affected part of the brain was 25 per cent higher than for both the control and ischemia-only group. NO is a molecule used by lining of blood vessels (endothelium) to signal to the surrounding muscle to relax – this dilates the blood vessel and increases the blood flow.

“We suggested that resveratrol may elicit neuroprotective effects by stimulating NO formation or release, which increases cerebral blood flow,” said Lu.

The authors said that further investigation of the effects of resveratrol was needed. Of particular interest is the dose needed to produce protection While resveratrol has been the subject of various studies, particularly in relation to heart health, recent studies have reported brain protecting effects from grape juice or wine – an effect linked to a synergy between the various polyphenols present.

A recent study using Concord grape juice by researchers from Tuft’s University reported that the combination of the polyphenols could decrease the effects of aging on the brain.

“It may be that the whole is greater than the sum of its parts,” lead author Barbara Shukitt-Hale wrote in the journal Nutrition (Vol. 22, pp. 295-302).

The amount of resveratrol in a bottle of red wine can vary between types of grapes and growing seasons. But nearly all dark red wines – merlot, cabernet, zinfandel, shiraz and pinot noir – contain resveratrol.

The health implications of red wine consumption appear to be filtering through to the consumer. A report from analysts Euromonitor in 2004 predicted that still red wine will exhibit by far the fastest growth in both volume and value terms between 2002 and 2007.

Their study claims that red wine is forecast to record global value sales of $82bn (€61.5bn) in 2007, a rise of some 31 per cent from 2002.

However, experts are quick to warn that moderation is the key. A study from Harvard University last year reported that people who have three or more alcoholic drinks per day have a significantly higher risk of stroke. Lowest risk was observed for those who had one, or maybe two, drinks every other day.