Red wine is this decade’s miracle cure. It helps protect us from colds, herpes, heart disease, diabetes, and liver problems. (But it’s not clear how much helps. And it’s not even clear what it is that’s helping.)

Dr. Roger Corder talked about his findings, originally published in the journal Nature last fall, at the Robert Mondavi–sponsored Taste³ conference in Napa Valley in early May. The good news: Red wine does promote a healthy heart. But not all red wine is equal. In fact, fashionable wines—ripe and high in alcohol—are dramatically less healthy. This news hit with a thud in the auditorium in Napa Valley, where big reds have become the rule, not the exception.

Corder’s detective work took him to two places: Gers in the southwest of France, and the Italian island of Sardinia, where the natives’ typical toast with red wine is “To live to 100.”

“Such a toast would probably not occur,” joked Corder, “if this didn’t happen with some regularity.” In both places, in fact, men and women lived to the century mark more than in other European spots. It’s not because of resveratrol, as has been widely reported, says Corder; his research found that there’s not enough of the compound in wine to do much good. But those long-lived Europeans did drink wine heavy with a compound call procyanidin.

The most famous wine of Gers is Madiran, a rustic, rough red wine made from the burly Tannat grape that hardly evokes swoons in oenophiles. The red wine of Sardinia is made from many obscure grapes, like Cannonau and Monica. While some popular grapes, such as Cabernet Sauvignon and Nebbiolo, are high in procyanidin, their levels are not near those of the Sardinian and Gers wines.

It’s not just the grape, though; it’s the way the wine is made. Corder recommends a return to traditional, old-world winemaking: lower alcohol, lower ripeness. “It’s a reality check,” he told me. “People need to realize that not all wines have the benefits. For one thing, procyanidin levels peak at a lower sugar level in these grapes. As the potential alcohol [i.e., sugar content] increases, the levels descend.” He also added that the elevated alcohol levels aren’t particularly healthy either.

Corder’s discoveries haven’t been received with completely open arms. Food scientist Dr. Harold McGee, author of On Food and Cooking: The Science and Lore of the Kitchen, told me that he’s not convinced. “I’m not sure that it’s going to be one magical chemical like procyanidin. It might be a combination of things. For instance, the people of southwestern France eat a lot of duck and foie gras, foods that are high in folic acid. Folic acid is known to be good for one’s arteries.”

Can they put folic acid in red wine? Perhaps that will be Corder’s next study. His book, The Red Wine Diet, is out in England and is soon to be released in the United States. It rates hundreds of red wines based on their healthiness. While not every wine producer will be able to cash in on the red wine health bonanza, perhaps Corder will.