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How does intense training affect Olympic athletes' gut health?

Olympians-in-training undergo intense and prolonged exercise routines, which can have surprising effects on the body.
by Contributor / / Source: LiveScience

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How do Olympic athletes' diets and exercise regimens affect their performance in the bathroom?

Olympians-in-training undergo intense and prolonged exercise routines, often accompanied by specific dietary requirements. But studies have shown these practices — especially in endurance sports, such as marathon running — can have adverse effects on the body and, in particular, on the gastrointestinal (GI) system.

Researchers have found rigorous training can not only lead to nausea, abdominal pain and diarrhea, among other physical symptoms, but also affect the bacterial communities living in the gut, which can carry additional implications for an individual's health, experts told Live Science.

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Perhaps the most extreme — and famous — example of an Olympian experiencing severe gastric distress mid-performance is French racewalker Yohann Diniz. While competing in the 50-kilometer (30-mile) walk final at the 2016 Olympic Games in Rio de Janeiro, Diniz collapsed with what appeared to be blood and feces running down his legs — though he still managed to finish the race in seventh place, Business Insider reported.

Pain in the gut

Gut distress is, in fact, "very common" among endurance athletes, with an estimated 30 to 50 percent of long-distance runners experiencing some degree of GI problems, according to a review published in May 2014 in the journal Sports Medicine.

In another study, heavy exercise was found to affect digestion in subjects who were "well-trained athletes," with intense workouts increasing the participants' stool frequency and affecting its consistency, scientists reported in March 2011 in the Scandinavian Journal of Gastroenterology.

Stress generated by endurance training or extreme exercise can produce an inflammatory response in the gut, which can lead to diarrhea, bloating and abdominal pain, Kim Barrett, a distinguished professor of medicine at the University of California, San Diego, told Live Science. Endurance training also diverts oxygen flow from the gut to the muscles, which can disrupt healthy GI function, Barrett said.

"The gut doesn't have enough oxygen, and that can cause injury to the lining of the bowel," she said.

Serious diarrhea symptoms can also lead to dehydration, which will not only affect an athlete's performance but can have serious health consequences as well, Barrett said.

Not only runners

While gastric stress is widely recognized as the bane of long-distance runners, far less is known about the extent of GI symptoms in other athletes, such as hard-training Olympians, and the problem may be more widespread than previously suspected, scientists reported in an editorial published in October 2017 in the British Journal of Sports Medicine.

The researchers surveyed 249 "elite athletes" from sports that included cycling, horse racing, rugby, tae kwon do and ultramarathon running. They found 86 percent of their subjects described at least one GI symptom, and 15 percent described one symptom — and sometimes more — as being "moderately severe" or worse. About 48 percent reported abdominal bloating, 44 percent described gassiness and 21 percent noted the presence of diarrhea.

Such a high prevalence of symptoms suggests health professionals should take a closer look at how the gut is affected by intense training and dietary practices across a range of athletic disciplines, the scientists concluded.

Meddling with the microbiome

Athletic training may also bring changes that affect the microbes in the digestive system, and the change in gut microbes may actually benefit the athlete, Barrett noted.

"In athletes of all stripes, there's a positive effect where the microbiota appears to change in a way that makes it more diverse, and there's also an increased representation of microbes that harvest energy from the diet," she said.

According to a review article published in March 2017 in the journal Oxidative Medicine and Cellular Longevity, exercise can increase gut microbial diversity and encourage beneficial microbes to flourish. In particular, exercise promotes a beneficial balance between populations of two gut microbe groups: the genus Bacteroides and the phylum Firmicutes. Imbalances between these groups have been linked to certain GI disorders and obesity, the review authors wrote.

However, far more research will be required in order to uncover the ways athletic training changes the gut microbiome and how these shifts in the microbial balance affect athletes' metabolism — and perhaps their performance, Barrett told Live Science.

"The flip side of this is, are the microbes doing anything that benefits the exercise?" Barrett said.

"Clearly, there's communication between the brain and the gut — beneficial effects of microbes on exercise could be related to changes in mood and cognition," she said.

"There are some very preliminary studies in mice showing that if you change the microbes in their guts, they can endure longer exercise bouts — but that's only in animals at this point," Barrett said.

This article was originally published in Live Science.

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