Natural components found in grapes, called polyphenols, are thought to be responsible for these beneficial effects.
Around a third of the study participants had some resistance to ultraviolet light after eating grapes.
Around 10 per cent of them still had some resistance after they stopped eating grapes for four weeks, suggesting some people build up resistance to sunburn after eating grapes.
The same three metabolites, or molecules produced by the body, in urine were depressed in the group who had developed resistance to ultraviolet light.
One of these, called 2’-deoxyribose, is a particularly strong indicator of reduced sun damage.
Lead study author Professor John Pezzuto, of Western New England University in the US, said: “Let thy food be thy medicine and medicine be thy food’ dates back to the time of Hippocrates.
“Now, after 2500 years, as exemplified by this human study conducted with dietary grapes, we are still learning the reality of this statement … ”