Red wine contains polyphenols, including the celebrated resveratrol. These polyphenols are extracted by fermentation: hence, their concentration is much greater in wine than in grape juice. Since they come from the skin and seeds of the grape, there are not nearly as many in white wine.
Resveratrol acts on genes (called sirtuines) that are known to protect healthy cells against aging. It can also slow the three stages of cancer development—initiation, promotion, and progression—by blocking the action of NF-kappa B.