Every month, Dr. Jeffrey Sankoff to a recent study or set of studies to talk to the researchers, explain the process behind it, and break down the findings.
This month: A study that followed 33 ultrarunners in a 60km event to measure markers of inflammation in the blood and their relationship to GI distress.
Race nutrition is a popular topic of discussion and a frequent source of anxiety for triathletes. Specifically, fear of ingesting and retaining nutrition. This is because gastrointestinal (GI) distress is a common complaint among endurance athletes, including triathletes, and something that can undo even the most well-thought-out plans and undo months of training.
A recent publication may provide guidance for those who suffer from this common condition at events. The paper was a collaboration between researchers in the Netherlands, Norway and the United States and looked at ultramarathon runners participating in a 60km race. The researchers were interested in determining how often athletes complained of GI problems during the event and whether or not the type and amount of food ingested affected the frequency and severity of those symptoms. In addition, the scientists hypothesized a specific biological premise that leads to GI problems in athletes — and they set out to find evidence to prove or disprove that theory.
This is important because many reasons have been postulated to date as to why endurance athletes develop GI symptoms, but they have never been shown to be the cause of the problem.
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These authors believed that during exercise blood flow is diverted away from the organs of the GI tract and this would lead to inflammation and injury which in turn would cause all those symptoms that keep you from taking in extra nutrition. They wanted to prove this by measuring markers of inflammation drawn from the blood of the runners obtained before and after the event, looking for generic markers of inflammation that can be present anywhere in the body and for levels of a marker that very specific to the GI tract. Intestinal fatty acid binding protein or I-FABP is a marker in the blood that manifests itself in very specific conditions of inflammation and of damage to the organs and tissues of the gastrointestinal tract. By looking for this particular marker, the authors hoped to show that damage to the gastrointestinal tract was occurring and that this was the cause of GI symptoms.
So what did they find?
33 athletes participated in this study, 28 of whom were men, and nearly three quarters of them reported some symptoms of gastrointestinal distress. This could have been anything from nausea to abdominal pain to diarrhea. While so many experienced symptoms, few athletes reported them as particularly severe. In fact, on a 10-point scale of severity, with 10 being the worst, the average score was just 1.9 — so not exactly close to debilitating.
As for the markers of inflammation, blood samples taken before and after the event showed that the non-specific markers of inflammation did indeed increase, but this was true whether or not an athlete was suffering from gastrointestinal disease (this corresponds with previously reported research on exercise markers of inflammation). However, I-FABP levels did not increase even in those athletes with the worst GI symptoms. So gut-specific injuries and inflammation didn’t seem to be the mechanism that caused these symptoms.
The only thing associated with symptoms was the amount of food ingested during the event. In this regard, there was an inverse relationship. That is, the athletes who ingested the most food, and especially when that food was in the form of carbohydrates, experienced the fewest and least severe symptoms.
The reason for this seemed to be that when carbohydrates were ingested, it improved blood flow to the gut through several mechanisms and prevented many of the symptoms often associated with low blood flow.
This study should certainly be interpreted with some caution, as it was small and very few women were involved. Still, the findings are consistent with previously published research, although the specific results regarding increased carbohydrate consumption associated with fewer symptoms are new and interesting.
Despite these limitations, it’s an important idea that athletes who consume more carbohydrate-based nutrition do better with regard to GI symptoms. This suggests that triathletes who have experienced problems in the past should consider a race nutrition plan where they consume a greater amount of fuel earlier in their event and do so with carbohydrates as the preferred fuel.
While this study did not confirm the cause of the inflammatory nature of GI symptoms, it ruled it out, so the search for specific causes of this problem will continue.
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