Can the dietary supplement resveratrol add years to your life?

“Rediscover your youthful DNA…reawaken youthful activity with this revitalizing, age-defying regimen.”

To listen to the ResVitále company describe its resveratrol supplement, you’d think that turning back the clock was just a matter of popping some pills.

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“Extending lifespan was the source of a lot of the initial excitement about resveratrol,” says researcher Joseph Baur of the University of Pennsylvania’s Institute for Diabetes, Obesity, and Metabolism.

In 2003, Baur began working in the laboratory at Harvard University where researchers had recently discovered that resveratrol—which is found most notably in grapes (and the wine that’s made from them)—could activate enzymes called sirtuins, which are involved in aging.

When the Harvard group and other researchers gave resveratrol to yeast, fruit flies, worms, and fish, the animals and yeast lived longer. “Resveratrol also makes obese mice live longer than they would otherwise,” says Baur.

That could be because it helps keep them from dying of diabetes. “In mice, resveratrol lowers blood glucose levels and increases insulin sensitivity,” Baur notes. “But there is no evidence that resveratrol can extend the lifespan of healthy mice.”

Or people, obese or not.

Of Men, Not Mice

“We don’t have a clear answer on what impact resveratrol has in humans,” says Eric Ravussin, director of the Nutrition Obesity Research Center at the Pennington Biomedical Research Center in Baton Rouge, Louisiana.

It would take too long for researchers to give people resveratrol or a placebo and wait to see which group lives longer. Instead, they see if resveratrol can improve risk factors for diseases—like diabetes and heart disease—that can cut lives short.

So far, the results have been contradictory. Why?

“Most of the published studies involve only 10 to 30 subjects,” notes Baur. And they’ve used different doses of different resveratrol preparations in different kinds of people.

“Resveratrol is not a drug,” notes Ravussin. “It’s a dietary supplement that can vary from brand to brand, and some formulations may contain other plant compounds that could affect the results.”

Some of the best studies:

• At Washington University in St. Louis, among 29 normal-weight women in their 50s and 60s, those who took 75 milligrams of resveratrol every day for three months had no greater insulin sensitivity than those who got a placebo. Nor did resveratrol affect their body fat, metabolic rate, cholesterol, or markers of inflammation.

• In the Netherlands, when 11 obese men took 150 mg a day of resveratrol (the same formulation the St. Louis women took) for a month, they had greater insulin sensitivity, lower blood pressure, and lower levels of blood glucose and liver fat than when they took a placebo for a month.

• In a Danish study of 24 obese men, insulin sensitivity, blood pressure, and belly fat were no different in those who took a high dose (1,500 mg) of a different resveratrol formulation every day for a month than in those who took a placebo.

The Anti-Exercise?

Is resveratrol safe? “There haven’t been controlled studies to show that it’s safe to take for long periods of time,” notes Baur.

A recent study may have found one downside. Last year, Danish researchers assigned 27 sedentary men in their 60s and 70s to take 250 mg of resveratrol or a placebo every day while participating in a high-intensity aerobic and resistance exercise program.

After eight weeks, the resveratrol takers’ oxygen capacity (a sign of aerobic fitness) hadn’t improved as much as the placebo takers’. And blood pressure, triglycerides, and LDL (“bad”) cholesterol dropped only in the placebo takers.

The bottom line: Until we know more about resveratrol’s safety and effectiveness, save your money.

Sources: Nature 444: 337, 2006; Cell Metab. 8: 157, 2008; Cell Metab. 16: 658, 2012; Cell Metab. 14: 612, 2011; Diabetes 62: 1186, 2013; J. Physiol. 591: 5047, 2013.

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