To improve performance, athletes train their lung, heart and skeletal muscles by exercise training and apply various nutritional programs to provide the energy intake required for exercise. Well, is there any athlete who consider training the intestines that absorbs the nutrients, and is this possible?
The Intestine is an Athletic Organ
The intestine is an important athletic organ, as it mediates fluid and nutrient intake during exercise. Many athletes report experiencing upper and lower gastrointestinal complaints during exercise. In addition to adversely affecting performance, these ailments also pose health risks in severe cases. A memorable example, Australian marathon runner Derek Clayton experienced serious gastrointestinal problems (vomiting and diarrhea) that started 2 hours after the world record of 2:08:33 in 1969 and lasted up to 48 hours. The athlete, who later stated that he did not consume any fluid during the race, is thought to have suffered ischemic bowel injury with a serious decrease in blood flow due to dehydration.
Sports branches such as professional cycling races, marathons and triathlons continue for hours, days or even weeks and each one competes against time. This necessitates the nutrients, that the body needs, to be taken as quickly as possible to be able to continue the competition. Eating and drinking during a cycling competition is easier than other sports due to the ergonomics of cycling. However, during sports, performed with high speed and while standing, such as marathon or triathlon, eating and drinking becomes more difficult due to carrying food, finding the right time to eat, and the ergonomic conditions of the sport. Athletes who cannot consume any food/drink due to stomach disorders during exercise experience a decrease in performance due to lack of energy or dehydration. In such a situation, the optimal solution is to consume a reasonable amount of food/drink that does not cause stomach discomfort. However, there is another approach on the agenda that might work: To “train” the gut, an organ that can easily adapt to changes in our body, just like a muscle.
Training the Gut
Although the studies on the gut trainig are mostly conducted on animals, the research evidence is very strong. Several human studies showed that gastric emptying and stomach comfort can be trained, the feeling of fullness can be reduced, and even stomach emptying can be accelerated against a single food. To give a simple example; the participants of the eating competitions train their stomachs and during the competition the large amount of food taken in a short time makes them feel less discomfort. The current record in these competitions was the consumption of 69 hot dogs in 10 minutes. When the preparation process of the contestants to reach such a level is examined, it is understood that they do exercises that increase their stomach capacity by chewing a large gum for a long time and consuming large amounts of food / drink for weeks. Although these competitions do not have a scientific basis, they reveal the stomach’s ability to adapt.
As for bowel training; The intestine is sensitive to fluid and nutrient intake during exercise, hypovolemia, hyperthermia, hypoglycemia, hypoxia, and ischemia. With proper training and nutrition, the risk of gastrointestinal discomfort during exercise is minimized by ensuring rapid emptying of the stomach and rapid absorption of food/beverages. Studies have shown that the intestinal absorption capacity can be increased and again, better adaptation to a particular food type can be achieved. For example; With the consumption of a high carbohydrate diet, the activity of sodium-glucose transport inhibitors (SGLT-1) in the intestine increases over time, and better absorption and oxidation of carbohydrates are provided. Under normal circumstances, carbohydrate absorption during exercise is limited to approximately 60 grams per hour (when at least one type of carbohydrate is consumed, e.g. glucose). While an intake of more than 60 grams per hour is expected to result in carbohydrate accumulation in the intestine, it has been shown that the absorption of carbohydrate consumed during the activity increases (1).
How Long Does Gut Training Adaptation Take?
How long it takes for this adaptation to occur is still unknown, but significant adaptations have been observed in animal studies after only a 3-day dietary change. In studies conducted with humans, 2-week and 1-month dietary changes were applied (1,2). In terms of practical application; It is recommended to do gut training for at least one week, optimally 5-10 weeks (3). It may be preferable to do gut training once a week on a long training day, or it may be tested on a training day where the athlete’s diet on competition day is applied.
- Cox GR, Clark SA, Amanda J. Cox AJ, Halson SL, Hargreaves M, Hawley JA, Jeacocke N, Snow RJ, Yeo WK, Burke LM. Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling. Journal of Applied Physiology Published 1 July 2010 Vol. 109 no. 1, 126-134 DOI: 10.1152/japplphysiol.00950.2009
- Costa RJS, Miall A, Khoo A, Rauch C, Snipe R, Camões-Costa V, Gibson P. Gut-training: the impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance. Appl Physiol Nutr Metab. 2017 May;42(5):547-557. doi: 10.1139/apnm-2016-0453. Epub 2017 Mar 22. DOI: 10.1139/apnm-2016-0453
- Jeukendrup AE. Training the gut for athletes. Sports Medicine.