Sport nutition

Sport and digestive disorders

Par Nicolas Aubineau - 6 minutes de lecture

Sport and digestive disordersAny effort requires energy for the functioning of the muscles and the brain, but not only. This energy comes at the a time from the carbohydrates, the lipids and the proteins to varying degrees.


Moreover, water loss as the loss of minerals (sodium, magnesium, potassium…) and micronutrients by sweat are often very important, especially as the effort is long and/or intense and the atmosphere’s warm (Marathon des Sables, for example). Maximum losses to imply, in other words, that one will be in deficit at the end of the test no matter what! You need a nutritional strategy before, during and also after the effort. But beware, during exercise, you must take into account digestive disorders that are far from negligible in both the novice athlete of high level, amateur or professional.


For example, the field returns show than 30-50% of ultra runners (trail, 100km, marathon, long distance triathlon, ironman…) suffer from digestive disorders. Among digestive disorders, the most frequent are: gastro-oesophageal reflux (GERD), vomiting, stomach cramps, diarrhea, bloating, nausea, bleeding…


Regarding digestive disorders, the main causes are:

  • Intestinal ischemia ; there are 70 per cent of the VO2 max, the blood flow to the intestine is reduced by approximately 80% which creates abdominal pain (cramps), acute diarrhea and lower digestive bleeding. Indeed, blood is redistributed at the muscle level for immediate needs related to the effort, which creates a lack of oxygen for the digestive system.
  • Mechanical with the rebound of the bodies, the vibration and shock at the level of the abdominal wall (related to the impact of feet on the ground), especially during races, or very often during walking down portions.
  • Dehydration;
  • Intestinal permeability (« leaky gut syndrome » ) is defined as the uncontrolled passage of substances (bacteria, toxic, polluting, additives…) through the intestinal barrier. The exercise itself increases this phenomenon. When efforts are followed in frequency and intensity, the leaky gut syndrome may appear, corresponding to a chronic increase in intestinal permeability combined with a pro-oxidative and inflammatory state (see article oxidative stress) generally favouring a decline in the immune system. Also, for your information, the gluten intolerance, drugs, alcohol… can promote this syndrome
  • The super-high of food intake before, during, or after the exercise, especially carbohydrates (too concentrated, hypertonic drinks, uncontrolled gels, sports drinks, maltodextrin in loads…
  • Pre competitive meals too rich in lipids and/or fibres or whose time has been too short between ingestion and the beginning of the test;
  • A small chewing food causing a bad digestion and ultimately bad-assimilation.


What are the biggest mistakes to avoid regarding the prevention of digestive disorders?

  • The intake of anti-inflammatory non steroidal (NSAIDs) before the race;
  • The consumption of hypertonic drink before and during the race;
  • The consumption of energy drink (Red Bull, Monster energy..)
  • The consumption of a cold drink, or even, ice (optimal taken 10 to 15°C)
  • Dehydration because too many runners start drinking too late.
  • The power of the race should be tested in practice, upstream, to visualize which corresponds best to the athlete (tennis, handball, cycling, trailer, marathoner, triathlete…). Keep in mind that the strategy of your training partner isn’t necessarily the one that will suits you for the best.
  • The presence of allergens (peanuts, lupin, shellfish, soy..) or a sensitivity to the effort for example for gluten, lactose… must refer to a gluten free or lactose free diet, for example in pre competitive period.

TIPS : energy intake on long efforts (ultratrail, 100km, cycling, triathlon..) should represent a sizeable amount of carbohydrates per hour of effort. Energy drinks can meet these needs, but beware, they are not worth each other.


Sport and digestive disorderAs for energy gels in unique nutrition, from my point of view, their use must be only in extra. There are on average 3 gels per hour of effort to ensure correct carb needs, and 14 for sodium, very frequently, which is unfortunate for the intestinal sphere causing disorders (diarrhea, bloating..) in some sports, including runners…


About energy bars, the note is the same as for gel. As an sports drinks extra (see Homemade sports drink), it has the advantage of being better tolerated on the gastrointestinal level than gel.


To concretely reduce digestive disorders, feeding the athlete must follow some basic principles:

  • Hydrate yourself before the effort. At least drink 500mL of a dietary drink of effort (energy, and no energy) per hour of effort, in hypotonic version preferably
  • The liquid should take the form of 2-3 SIPs every 7 to 10 minutes. An optimal decision-making remains about 300mL.
  • Try to promote the most possible the liquid to the solid for given quantity and quality contributions: question of improved assimilation;
  • Organize your supplies in advance during your games: tennis, football, rugby, handball, basketball, or your races: cycling, marathon, triathlon, trail…
  • Completed possibly by a regular intake of energy bars if the effort is long (> 3-4 hours, every 1 to 2 hours, function of the supply of drink, the nutritional tactics adopted…) ;
  • Drink recovery drinks rich in proteins during the race (minimum 5g per hour of effort, amino acid connected) alternating with the dietary drink of the effort for the efforts of several hours (> 3-4 hours);
  • Moderate consumption of gels, just as a drink extra on the efforts of a few hours (< 3-4 hours);
  • Vary the taste: sweet and salty to minimize the phenomena of saturation, thus promoting drinks and limiting ultimately dehydration to the effort!
  • Perform phases of detoxification upstream and at the end of your sports seasons to rebalance your body, including the digestive level, acid-base balance…
  • Get an interest in probiotics (ferments) to promote your good intestinal balance, as well as the spices (turmeric, ginger, ginseng,…) and algae (Spirulina,…).


Conclusion on digestive disorders

Digestive disorders are the cause of a majority of dropouts of under-performance in the field. Finding solutions is a prophylactic approach for the sportsman in his quest for victories!


The performance does not only rely on the legs, head, training, material… but also on the digestive system! It is the « ground » which receives the food to digest nutrients, these being subsequently absorbed and, ultimately, assimilated at the cellular level. So, a single word: « take care of it! .»» It is not for nothing that the belly is known as our ‘ second brain ‘!  »

I’m still 100% convinced that good nutrition and optimal hydration remain both keys of vault, both complementary and synergistic, to a good prevention of digestive disorders. Always keep in mind that each athlete is unique and our individual characteristics make the environment different(dietary, psychological, technical, tactical,…), so « what applies to a person may not apply for the training partner ».
There is no standard model for everyone!


Sports Dietitian Nutritionist


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