Claims about the life-extending properties of a much-hyped ingredient in red wine and chocolate are unfounded, research suggests.
The antioxidant resveratrol, found in dark chocolate, red wine and berries, has no great impact on life span, heart disease or cancer, say scientists.
Lead researcher Professor Richard Semba, from Johns Hopkins University in Baltimore, United States, said there was a lot of hype about the health benefits of resveratrol but that wasn't backed up in the study.
Belief in the health-giving properties of resveratrol has led to a plethora of supplements containing the compound and the promotion of diets based on boosting its consumption.
Previous research has shown that resveratrol has an anti-inflammatory effect and can improve the health and lifespan of mice.
At the molecular level it mimics the effects of calorie restriction, which is known to lengthen the lives of some animals but not humans.
Some preliminary evidence also suggests the compound could help prevent cancer and reduce the stiffness of arteries in older women. But there is little real-world data to support links between resveratrol intake and improved human health, the researchers point out.
The research involved 783 Italians aged 65 and over who were in the Ageing in the Chianti Region study from 1998 to 2009.
Regular urine tests were carried out to look for breakdown products of resveratrol and see if their levels were associated with reduced cancer, heart disease and death rates.
During the nine-year follow-up, 268 (34.3 per cent) participants died and 27.2 per cent of those free of heart disease at the start of the study had developed the condition.
Of the 734 men and women who had no signs of cancer at enrolment, 4.6 per cent were later diagnosed.
But wine buffs and lovers of dark chocolate should not lose heart, say the scientists whose findings appear in the journal JAMA Internal Medicine.
"It's just that the benefits, if they are there, must come from other polyphenols or substances found in those foodstuffs," Professor Semba said. "These are complex foods and all we really know from our study is that the benefits are probably not due to resveratrol."