This story was originally published in the August 2011 issue of Men's Journal

In 2011, Novak Djokovic became the hottest tennis player on the men’s tour, winning 43 of 44 matches and closing in on the number one world ranking. His secret? The 24-year-old Serb credits his remarkable breakthrough to a simple dietary change: He stopped eating gluten, a protein found in wheat, rye, and barley, and as common in baked and packaged foods as flour or oil.

Djokovic’s story is not unique. A growing number of athletes, dieters, and nutritional trendsetters attribute going off gluten to a host of health benefits, including improved performance, reduced inflammation, better digestion, and weight loss. “My joints feel much better, and my post-game recovery is as good as it has ever been,” says eight-year NBA veteran Kyle Korver of the Chicago Bulls, who went gluten-free in 2010. “I definitely have more energy and just feel cleaner.” Clean living is exactly why Tony Horton, creator of the poplar home-fitness program P90X, tries to avoid gluten, while New Orleans Saints quarterback Drew Brees follows a gluten-free diet because of problems with both wheat and gluten. Even entire teams like pro cycling squad Garmin-Cerv?lo are gluten-free.

A decade ago, few people without a master’s in nutrition had ever even heard of gluten, but today, giving up gluten is nearly ubiquitous. Gluten-free food manufacturers, bakeries, and even chain restaurants like Outback Steakhouse and Boston Market offer wheat-free alternatives to breads, pasta, cereals, and even entire meals, as sales of gluten-free foods hit an exorbitant $2.6 billion in the U.S. last year. With all the hype ? and no end in sight ? it’s hard not to wonder: Should you should be going gluten-free, too?

For anyone with celiac disease ? also known as gluten intolerance, an autoimmune disorder that causes the body to react to gluten by damaging the intestinal tract ? going gluten-free is a necessity. The estimated 1 percent of the population who have celiac often suffer from diarrhea, constipation, migraines, joint and muscle pain, skin rashes, and sinus infections. But because “symptoms can range from severe to hardly noticeable and are so similar to other digestive conditions, misdiagnosis remains rampant,” says Dr. Peter Green, director of the Celiac Disease Center at Columbia University Medical Center. So while the condition can be diagnosed with a blood test, it’s thought that only 5 percent of Americans with celiac are aware that they have the disease.

The more common condition ? and reason sales of gluten-free foods have gone through the roof ? is gluten sensitivity, which triggers an immune response to the protein that causes symptoms similar to, but less severe than celiac. Recent estimates suggest that up to 10 percent of the U.S. is gluten-sensitive, but because there is no diagnostic test for the condition and symptoms vary so widely, experts aren’t exactly sure how widespread it is. It’s also difficult to discern if the number of people with gluten sensitivity has increased or, rather, only awareness of the condition.

Until a blood test is developed, the only way to identify gluten sensitivity is to eliminate all foods that contain gluten for seven to 10 days. If you have more energy, your regular headaches disappear, or just feel better during the elimination diet, you may have a sensitivity ? but not always. Because going gluten-free means avoiding most fast foods, processed snacks, and refined carbohydrates ? which, in themselves, can cause fatigue, weight gain, and other digestion problems ? it’s difficult to tell if people feel better because they’re not eating gluten, or simply because they’re eating healthier. “By yanking processed packaged foods from your pantry and cooking more of your own meals, a gluten-free diet can end up being a healthy switch for some people,” says Brian Higginson, a clinical nutrition specialist in Seattle. “So you could feel great on a gluten-free diet, even if you don’t have a sensitivity.” To rule out the possibility that an elimination diet relieved your symptoms only because you stopped eating preservatives and processed foods, continue to avoid refined and fast food for at least one week after reintroducing gluten into your diet.

Furthermore, there’s no substantial research to prove that a gluten-free diet causes the effects its advocates say it does. “Studies don’t back up anecdotal evidence that ditching gluten increases energy levels, boosts exercise performance, improves digestive health, or quells muscle inflammation in people who don’t have symptoms or a diagnosis of gluten sensitivity,” says Cleveland-based dietitian Katie Heddleston, who specializes in seeing gluten-free clients and is also gluten-free herself because of an intolerance. She says that it’s a misconception that digestive trouble is a surefire sign of a gluten sensitivity. Another misunderstanding is that the diet helps promote weight loss. “A lot of this stems from eliminating foods ? and in turn calories ? from your diet.”

Despite their health halo, not all gluten-free foods are good for you. “Some gluten-free products actually have more fat, sugar, or sodium than their traditional counterparts, while others are made from highly processed gluten-free flours like white rice,” says Heddleston, adding that “gluten-free cookies and cakes made with hydrogenated fat aren’t a good choice for anyone.” And without careful planning, many athletes may miss out on the nutrients they need for optimal performance, she says.

Going without gluten isn’t easy, either. Because of the protein’s use as a thickening agent, food manufacturers add gluten to a dizzying array of foods, including ketchup, veggie burgers, sausages, ice cream, soy sauce, and even vitamin supplements. What’s more, since gluten is also found in rye and barley, simply avoiding wheat won’t do the trick. “To adhere to a gluten-free diet, you have to become very adept at reading labels to understand that products labeled ‘wheat-free’ aren’t necessarily ‘gluten-free,’?” concludes Heddleston.

But recent converts like Kyle Korver don’t mind the constant vigilance required to be gluten-free. “My body has never felt this good at the end of a season.”