We keep hearing about the benefits of drinking red wine. Why not grape juice instead? It has the same benefits, plus no alcohol.

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Red wine is probably better for you than grape juice because the fermentation process involved in making wine changes the makeup of the juice, and the skin of the grape, which is loaded with healthful antioxidants, is more likely to be used in the winemaking process, said Dr. Antonia Trichopoulou, a professor and director of the World Health Organization Collaborating Center for Nutrition at the University of Athens School of Medicine in Greece.

The color of the wine indicates how many healthful nutrients known as polyphenols the drink contains. “Red has more than white, and white more than beer,” said Dr. Miguel Ángel Martínez González of the University of Navarra in Spain. Red wine also contains alcohol, and many observational studies have shown that drinking alcoholic beverages in moderation reduces the risk of coronary heart disease, he said, by increasing levels of healthy HDL cholesterol and reducing the clumping of platelets that can lead to clots inside blood vessels.

A compound that may be responsible in part for wine’s health benefits, called resveratrol, is also present in grape juice. But it’s almost impossible to tell how much there is in a particular glass of wine or grape juice, and naturally occurring levels of resveratrol may be too low to have a pronounced effect on health, said Leonard Guarente, who studies the biology of aging at M.I.T.

“There’s a tremendous variability in the amount of resveratrol even from one wine type and one batch to another,” said Dr. Guarente, who started a company that sells supplements that contain a resveratrol cousin.

Grape juice is also high in sugar, and people tend to drink a lot of it, which could be unhealthy, said Sara Baer-Sinnott, president of Oldways, a nutrition organization that advocates eating the Mediterranean diet.

“Grape juice is a good thing in moderation,” she said, remembering that when she was a child she used to drink it in tiny Dixie cups.

The bottom line, Dr. Guarente said, is that there is plenty of scientific research linking red wine to health benefits, but no similar studies in grape juice. “There may be some synergy between resveratrol and something else present in the wine and not in the grape juice,” he said.