Exercise. Eat nutrient-packed foods. Reduce caloric intake. These are the three measures that health experts have long touted as the simple, yet effective keys to weight loss. But for those who lack the free time to hit the gym or the extra cash to spend on fresh produce, whole grains, and lean proteins, these golden rules might feel a bit inaccessible. One solution some reach for? Supplements.
Approximately 15 percent of U.S. adults have used a weight-loss dietary supplement at some point in their lives, and women are twice as likely to use them than men, according to the National Institutes of Health. Aside from the run-of-the-mill offenders such as caffeine and Orlistat is resveratrol. This antioxidant compound can be found naturally in red wine, red grape skins, purple grape juice, mulberries, and in smaller amounts in peanuts, and has been used as a way to enhance an already healthy lifestyle.
In fact, sales of resveratrol supplements were estimated to be $49 million in the United States in 2019, and the market share is expected to grow about eight percent between 2018 and 2028, according to Future Market Insights. Much of the initial excitement about resveratrol began in 1997. Its potential to protect the cardiovascular system, prevent cancer, and expand lifespan, among others, has been gaining interest ever since, says John M. Pezzuto, Ph.D., D.Sc., dean of Long Island University’s College of Pharmacy and a resveratrol researcher.
Today, resveratrol supplements are being promoted as a way to boost energy, maintain body weight, and increase muscle endurance. But how effective—and safe—is it, really?
Resveratrol Supplements and Your Health
Among the ongoing medical explorations, one of resveratrol’s most immediate possibilities lies in the realm of fitness. “Looking at the research so far, though more is needed, resveratrol has unprecedented promise for improving people’s physical endurance and helping them control their weight,” says James Smoliga, Ph.D., associate director of the High Point University Human Biomechanics and Physiology Laboratory in High Point, North Carolina. Resveratrol is a source of high hopes, though much about it remains unknown.
“Even though I’m leery when I hear something described as a panacea, I feel very positive about recommending resveratrol because of the research behind it,” says certified trainer Rob Smith, founder of the Body Project, an Eagan, Minnesota personal-training studio.
Yes, there is a plethora of research on the resveratrol-weight loss connection, but most of it is on animals. What these studies have shown, however, is encouraging: Resveratrol appears to activate enzymes that help muscles use oxygen more efficiently, a performance enhancement known to runners as higher VO2 max. (In simplified terms, the higher your VO2 max, the lengthier and more intense the workout you can handle.) “When you process energy more efficiently, you increase endurance,” says Smoliga. “I take it myself and definitely have more stamina because of it,” says Smith, who estimates that 40 of his clients also take the pill. “I can see that they’re able to push themselves further than before.”
Resveratrol’s Get-Fit Promise
Fitness experts started to take notice of resveratrol in 2006, when the journal Cell reported that mice given the antioxidant ran nearly twice as far on a treadmill as unsupplemented critters. The treatment “significantly increases the animal’s resistance to muscle fatigue,” researchers concluded. Translation: More energy and less muscle exhaustion led to a better workout. “It’s as if you could put the benefits of a healthy diet and exercise in a pill,” says Smoliga.
The hypothesis? Resveratrol stimulates enzymes called sirtuins, which control important functions throughout the body, including DNA repair, cell life, aging, and fat production. “Sirtuins may also increase mitochondria, the powerhouses inside cells where nutrients and oxygen combine to make energy,” says Felipe Sierra, Ph.D., director of the division of aging biology at the National Institute on Aging at the National Institutes of Health. Sure enough, mice on resveratrol had bigger, denser mitochondria, so their charged muscles were better able to use oxygen. In theory, this means that resveratrol may be able to help you work out longer or harder (or both) before your muscles become too fatigued to perform. These more intense workouts will then condition muscles for an even greater effort the next time you lace up, for a continuous cycle of improved fitness.
Again, research outside the laboratory has been limited: In one of the few completed human trials, 90 sedentary men and women were given a resveratrol-based cocktail or placebo daily for 12 weeks. After three months, everyone jumped on treadmills. “While they all hit the same levels of intensity, the resveratrol group exerted less effort while exercising,” says Smoliga, who led the study. What’s more, they also had significantly lower heart rates during exercise—the equivalent of the results of three months’ light to moderate training—apparently just from taking the daily supplement.
Resveratrol Supplements and Weight Loss
For all the evidence about resveratrol’s exercise benefits, manufacturers’ claims that the supplement helps people lose or maintain weight are harder to substantiate.
Some proponents say the resveratrol-weight loss link works in part by interacting with blood sugar. “Studies show that resveratrol boosts your muscles’ ability to absorb glucose from food. This means that more calories go into muscles and fewer go into fat cells,” says Smoliga. Indeed, research presented at a conference of the Endocrine Society showed that in the laboratory, resveratrol inhibited the production of mature fat cells and hindered fat storage—at least at the cellular level. In addition, a study found that mice fed a high-fat diet with resveratrol weighed almost the same as those served a non-high-fat diet without the supplement. But because, for some, resveratrol appears to increase the ability to exercise more frequently and intensely, it’s hard to pin down the real source of weight maintenance.
Other hypotheses include that resveratrol could function as an “energy restriction mimetic,” meaning consuming resveratrol would be equivalent to going on a diet and reducing caloric intake, says Pezzuto. In a 2018 study, mice were fed a high-fat diet to become obese, then either exercised alone or exercised with resveratrol supplementation. “Relative to exercise alone, the combination did not result in any greater weight loss, but some metabolic markers were slightly improved,” explains Pezzuto. Still, in order to achieve the same marginal effect in humans as was shown in the mice, the equivalent dose would be nearly 90 grams (90,000mg) per day. (For the record, resveratrol supplements on the market typically contain 200 to 1,500 milligrams of the antioxidant, and red wine contains roughly two milligrams per liter.) “For an obese individual, this dose could be doubled,” says Pezzuto. “Obviously, not practical.”
Other studies performed on rodents fed a high-fat diet and supplemented with resveratrol have shown slight decreases in body weight; however, the inconsistencies in dosage across studies means these results aren’t definitive. What’s more, in another study of mice that were fed a normal diet with or without resveratrol for 15 weeks, resveratrol didn’t lead to any statistically significant changes in body weight at all.
Overall, the efficacy of resveratrol weight loss supplements is inconclusive. After reviewing nine studies conducted over a 15 year period, researchers concluded that there was not enough evidence to support the recommendation of resveratrol supplementation to manage obesity, as these studies showed no significant change in BMI and body weight or improvements in fat mass, fat volume, or abdominal fat distribution.
“Ultimately, like every other drug or dietary supplement associated with a health claim, the only real, meaningful evidence results from a properly conducted clinical trials with human beings,” says Pezzuto. And the evidence-based answer may come soon enough, as more than 100 clinical trials on resveratrol are currently being conducted with human participants.
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Safety Concerns Over Resveratrol Supplements
Establishing supplement safety can take decades, and over time, in some cases, surprising dangers can be revealed. “Not long ago, vitamin E was all the rage,” says Christopher Gardner, Ph.D., associate professor of medicine at Stanford University School of Medicine’s Prevention Research Center. Vitamin E is an antioxidant thought to help protect against a range of diseases, similar to the hopes for resveratrol. But one report found that high doses of E could actually increase the risk of death. “It took 30 years to show that vitamin E supplements may have had negative effects in the large amounts that were often recommended,” notes Gardner.
And the safety of resveratrol supplements has yet to be proven. While one human study found that ingesting a one-time dose of up to five grams had no serious ill effects, that experiment lasted only a day. (Of course, most people who try resveratrol take more than one dose.) “The studies are too short,” says Sierra. “We just don’t have any data on long-term effects in people.” (Not to mention, dietary supplements aren’t regulated by the FDA.)
Pezzuto notes that there isn’t any evidence suggesting that taking resveratrol (specifically at the low doses found in most supplements on the market) can cause any harmful side effects. Likewise, daily doses of up to 1500mg for up to three months is possibly safe, according to the U.S. National Library of Medicine. Taking 2000 to 3000mg of resveratrol daily, however, may cause stomach problems,
“In other words, there’s no compelling reason to recommend against taking resveratrol for weight control or any other purpose, but at the same time there is no compelling reason to expect any miraculous outcome,” he says.
What is proved to be safe and healthy: consuming moderate amounts of natural sources of resveratrol. “Because of the unknowns, I’d rather people enjoy a glass of wine now and then instead of taking supplements,” says Gardner. And research suggests that moderate amounts of wine can lower the risk of cardiovascular problems. Red wine has the highest concentration of resveratrol with as much as 15mg per bottle in types like pinot noir (depending on grapes, vineyard conditions, and other factors), but the content even in wine ranges widely; grape juice has about a half milligram per liter; and cranberries, blueberries, and peanuts contain trace amounts.
With no true consensus on the ideal amount of resveratrol necessary for measurable fitness perks, many experts advise proceeding with caution. “Do you really want to experiment on yourself?” asks Sierra, who advocates staying healthy sans supplements. Thaat opinion is shared by many wellness pros, including Jade Alexis, certified personal trainer and Reebok Global Instructor. “I typically frown on these seemingly quick, easy fixes,” Alexis says. “I believe that eating right, exercising regularly, and getting sufficient sleep will keep us healthy.” (And help you lose weight if that’s what you want.)
What to Know Before You Take Resveratrol Weight-Loss Supplements
Take an Rx inventory. Studies suggest that the supplement could increase the risk of bleeding if you’re taking blood thinners, anticoagulants, or nonsteroidal anti-inflammatory drugs. Resveratrol may also interfere with the body’s ability to metabolize various meds, including statins, calcium channel blockers, and immunosuppressants, potentially causing a toxic buildup of medication. Talk to your doc before taking any supplements. (See: Dietary Supplements Can Interact with Your Rx Meds)
Check the label. Look for products that contain trans-resveratrol, which is found in nature. Beware of words like complex, formula, and blend, which indicate a mix of ingredients that may include only small amounts of resveratrol.
Buy tested brands. These products have passed purity and ingredient tests performed by
ConsumerLab.com, an independent company that checks supplements.