Going gluten-free may not do anything to improve athletic performance, a small study of cyclists suggests.
Jumping on the bandwagon
Eliminating grains like wheat and rye that contain the protein gluten has become a trendy extension of popular carb-cutting diets. A growing number of athletes are jumping on the bandwagon because they believe it may improve endurance and stamina.
But when Australian researchers put a group of elite cyclists on a gluten-free diet for one week, their performance was no better than it was during a week of eating foods containing wheat, the study found.
"There is no evidence to suggest that gluten removal itself is linked to improved health or performance outcomes," lead study author Dana Lis, a health sciences researcher at the University of Tasmania, said by email.
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Lis and colleagues studied the gluten-free diet in 13 athletes who didn't have coeliac disease, a digestive disorder that damages the small intestine and interferes with absorption of nutrients when people eat foods containing gluten.
About one in 141 Americans has the disease, according to the U.S. National Institutes of Health. It can be detected with a blood test for antibodies that show an immune response to gluten, and may also be confirmed by a biopsy of the small intestine.
People with coeliac disease are advised to go on a gluten-free diet to ease symptoms such as abdominal pain, bloating, gas, diarrhoea, anaemia and weight loss.
Symptoms didn't vary
Because athletes in the study didn't have coeliac disease, a medical reason to eliminate gluten, it's not surprising that a diet free of this protein had no benefit, Lis said.
Researchers gave the athletes gluten-free meals during the study, and then tested their reaction to the protein by supplementing one week of meals with protein bars containing wheat or another source of gluten.
Each day, the athletes completed questionnaires about their digestive health. Over the course of the study, symptoms didn't vary based on the type of diet they followed.
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The cyclists also did exercise tests at the end of each week-long diet, and there was no difference in their performance based on whether or not they consumed gluten, the researchers report in the journal Medicine and Science in Sports and Exercise.
Blood tests done at the end of each diet also failed to detect a difference in inflammation based on what the cyclists ate. Eliminating gluten can relieve inflammatory bowel disorder for people with that condition, but none of the athletes included in the study had it.
If athletes are indeed gluten intolerant, which is rare, they would benefit from a gluten-free diet, said Nancy Clark, a sports nutritionist in private practice in Boston. In that small subset of people, cutting out gluten can curb inflammation, ease digestive symptoms and potentially boost performance, said Clark, who wasn't involved in the study.
A step in the wrong direction
But a gluten-free diet should be the exception, not the rule, she said.
"A lot of these athletes are eating this diet for no reason, limiting their intake of foods, and a lot of gluten-free packaged foods are really trashy so it's actually a step in the wrong direction," Clark said.
It's possible some athletes perceive a benefit because when they go gluten-free, they also become more conscious of what they eat, consuming more fruits and vegetables and avoiding processed foods, Lis said. It's the generally healthier diet, though, not the absence of gluten, that makes them feel better.
Because the current study is small and limited to cyclists, it's hard to say for sure without larger trials whether the impact of gluten would be similar for other athletes or people who don't play sports, said Dr. Robert Dimeff, past president of the American Medical Society for Sports Medicine and an athletic health researcher at the University of Texas Southwestern Medical Centre in Dallas.
"This is just another fad diet that science doesn't support at this time, especially when it comes to athletic performance," said Dimeff, who wasn't involved in the new study. "The take home message at this time, whether you're an athlete or not, is eat whole natural foods and don't worry about gluten unless you are actually gluten-intolerant."
SOURCE: http://bit.ly/1Mm8c4u Medicine and Science in Sports and Exercise, online May 12, 2015.
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