Gluten-free diets have become popular among runners and other athletes. Just how popular is not known, but 41 percent of more than 1,400 athletes who completed a recent scientific survey administered by researchers at the University of Tasmania reported eating gluten-free most or all of the time. (Self-selection bias probably inflated the percentage of gluten-free participants relative to the general athlete population.) Seventy percent of the survey respondents identified themselves as endurance athletes. None of them had Celiac disease, a rare, genetically based disease where the consumption of gluten—a protein in wheat—provokes an immune reaction that damages the intestinal lining.

Among non-athletes, the most common reason for adopting a gluten-free diet is a self-diagnosis of gluten sensitivity, which causes gastrointestinal discomfort after wheat is consumed. A majority of the athletes participating in this survey went gluten-free for the same reason, but many had a different or secondary reason. Based on this finding, the creators of the survey concluded that the choice to go gluten-free “may be driven by perception that gluten removal provides health benefits and an ergogenic edge in NCA [nonceliac athletes].”

This perception was a cause for concern among the researchers because, at the time the survey was conducted, there was no evidence that removing gluten from the diet would provide an ergogenic edge (i.e. enhance athletic performance). In fact, there wasn’t even a theory as to how removing gluten from the diet possibly could enhance athletic performance. Nevertheless, the lack of evidence or a proposed mechanism for such an effect did not rule out the possibility that a gluten-free diet might somehow give athletes a performance boost. So the same researchers did a follow-up study to find out if it did. The results have just been published in Medicine & Science in Sport & Exercise.

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The participants in this new study were 13 competitive cyclists, eight men and five women. None of them had Celiac disease or a history of GI problems. All of the cyclists were placed on a gluten-free diet, but half supplemented this diet with food bars containing gluten (supplying 16 grams of gluten per day) and the other half supplemented the same diet with gluten-free food bars. They were not told which bars they had been given.

After seven days, the subjects went back to their normal diet for a 10-day “washout” period and then spent seven days back on a controlled diet and eating whichever bars they hadn’t received in the first part of the experiment. At the end of each seven-day intervention all of the cyclists completed a performance test consisting of 45 minutes of indoor cycling at 70 percent of peak power followed immediately by a 15-minute time trial. The subjects completed this time trial neither faster nor slower after a week of gluten-free eating than they did after a week of eating gluten. The authors of the study expressed no surprise at this result because, again, there is no physiological reason to expect a gluten-free diet to elevate performance.

Throughout period of the study, the researchers also collected information from the participants on GI systems experienced both during and outside of exercise as well as indicators of intestinal injury and markers of inflammation (there is some evidence that gluten promotes inflammation even in healthy individuals). The removal of gluten from the diet of these athletes had no effect on any of these variables.

These results suggest that most athletes will experience neither performance nor health benefits by going gluten-free. So it appears that the only scenario in which you might benefit from removing gluten from your diet is if you experience gastrointestinal discomfort after eating wheat. In that case it will be worthwhile to remove wheat from your diet and see if the symptoms resolve. If they do, keep going. If not, make an appointment with your physician for help in getting to the bottom of your problem.

One word of caution: If you do remove wheat from your diet for any reason, don’t make the increasingly common mistake of eliminating all other grains as well. Grains are the most concentrated food source of carbohydrate, which runners need to fuel their training and recovery. Runners who go grain-free often develop signs and symptoms of overtraining syndrome, including persistent fatigue and declining performance.

Finally, even if you have no digestive issues, you may want to consider eating less wheat and more whole grains of other types, for reasons that have little to do with gluten. Most of us in this society eat a lot of wheat, and while it’s good stuff, no food is good in excess, whereas there is no such thing as excessive dietary diversity. Amaranth, anyone?

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