Digestive problems during Ultra Endurance

By Corinne PEIRANO, Dietician - Nutritionist

Nutritional comfort while running requires one to establish a food strategy so as to live the event comfortably. Nothing must be left to chance. We should thus have tested before “D” day ", as a nutritional training, the provisions consumed during the race: gels, drinks, solids, all the food met at the refreshment points.

If you are vulnerable to digestive problems while running, you will have to get organized so as to best plan your food, the most adapted to your digestive tolerance, then to determine your tastes, your cravings which tend to evolve as the  kilometres unfurl, while taking into account your specific needs (when, how much and what to eat, what and how much to drink) with as an additional parameter to be managed, according to the race, one or two nights, even more, without sleep.

I - Food and hydration at the heart of the problem

It is indispensable to review what you eat by noting the food errors before and during the effort (for digestive disorders with nutritional constituent), to revise the healthy-dietary markers (quantitative, qualitative, respecting the 3 hours of digestion, before competition, rule) and the nature of the food (tendency for too many carbohydrates even "force-feeding" slow-burning sugars by sportsmen of stamina).

Not forgetting Hydration for which it is advisable to establish a dehydration diagnosis (physical aspect, weight (weighed before and after training), frequency, volume and colour of urine or concentration)

II - Objectives: be successful with ones Nutrition and Hydration during a race

Set yourselves an objective:

  • Preservation of ones nutritional state and  hydration during the race is a success factor for an ultra-stamina race
  • Regular hydration is a key factor against digestive problems. Dehydration produces a fast decline of muscular strength and stamina capacity (weight loss 1 to 2 % = loss of physical ability of 5 to 20 %)
  • The battle against dehydration is an absolute priority but difficult to ensure. The runner has to hydrate as a preventative measure even if, at the beginning, his urinary flow increases (awkward for competitions). Advice: drink 150ml just before the start, that is to say the equivalent of a beaker, the water will be quickly sweated off, 8 to 10 minutes afterwards.
  • Estimate and plan well the energetic needs of the runner
    • If energy intake > requirement = in cell inhibition enzymes metabolism energy-giving (before/during/after the race)
    • If energy intake < requirement  = risk of collapse of the energy-giving mechanism in race (Hypoglycaemia: decrease of attentiveness, problems with concentration,  paleness, asthenia)

III – Strengthen the digestive system

The consolidation of the digestive system is to be looked at first because it is the runner’s "Achilles' heel, weak link ". There are diverse routes to explore :

  • Digestive problems (stomach and intestines) are sometimes due to an allergy  to the effort in connection with a food eaten during the race (prawns, wheat...) This allergy is known as Nutritional Anaphylaxis  Induced by Effort,  elimination of the bacterium Helicobacter pylori, possible ulcerations or other organic damage, possibly be screened for the gluten and\or lactose intolerances …
  • Take into account the total digestion time: between 6 hrs, 8 hrs and 24hrs (and +) according to the nature of the food eaten  the previous day, or even two days before the race
  • Intestinal Flora: the digestive system is colonized by 100 000 billion bacteria which is comprised of 400 different species of flora (≈ 2 kg of body weight) involved in immunization defence ( intestinal mucous protection) and good bowel function

A weakened digestive system can entail hyper permeability of the intestinal mucous membrane, stress caused by dehydration and unsuitable training, overtraining, or an unhealthy lifestyle. This can give rise to alternating episodes of constipation and diarrhoea.

To reinforce the intestinal flora, opt for Probiotics: "living micro-organisms which consumed in adequate quantities produce a benefit for the host’s health" (definition OMS, FAO).
What are their effects?

  1. Daily battle with bowel functions (accelerations, slow-downs, bloating)
  2. Reinforcement of the immune system (production of a mucus and protective antibodies ( IgA) on the intestinal barrier)
  3. Purification of the intestinal flora (fight against pathogenic bacteria, parasites and fungi (e.g.: Candida albicans)
  4. Stimulation of the production of group B vitamins and vitamin K

IV - Improving the dietetics of the runner in everyday life

Nutrition and Hydration

Prioritise certain foods, moderate or temporary eviction of foods (before race: animal milk, gluten, Soya or eggs in case of allergy during effort)

A varied diet, balanced and healthy

Prioritise a varied, well-balanced and healthy, diet (food with a low GI). Pleasure Foods hyper-carbohydrates have to be very occasional (chocolate, biscuits, cakes, pastries, croissants and similar products, food with refined sugars or salts, or fatty, salty or sweet foods)

Four important points

  • The helpings on the plate must be adapted to the runner’s hunger  (≠ helping XXL)
  • The pattern of the meals must be regular  : 3 meals/day + 1 snack
  • The acid-base balance must be respected (alkali food)
  • No excessive  pleasure food

V - Pre-competition: nutritional strategy (see page "Dietetics and nutrition")

It is recommended that runners, who have a digestive sensibility accompanied by digestive disorders during a race, temporarily follow (before the race) a diet without waste or less strict, a diet of digestive savings (modelled on the hospital diet - gastroenterology, digestive surgery services)

> Two days before the race day: Food which is going to spare the digestive system:

  • Cut out for two days food containing vegetable fibres to obtain an evacuation of the colon and to avoid diarrhoea during the race
  • Recharge carbohydrates with bread and cereal products at every meal

Recommended foods

  • Dairy products: fromage blanc (creamy soft cheese), yoghurts (goat, sheep), hard cheese cooked (parmesan, comté, gruyère). Soya yoghurts (containing neither milk nor lactose)
  • Meat and fish, shellfish, eggs (in all forms for the latter)
  • Firm fleshed potatoes: charlotte, amandine, noirmoutier, ratte…
  • Refined cereals : white rice, pastas, semolina, white flour, cornstarch, tapioca, quinoa
  • Bread : white bread, white sandwich bread, Viennese bread, dry biscuits (sponge fingers, petit brun), rusks(without cereal or enrichment), cakes/pastries without fruit
  • Fats : butter, olive oil , rape seed oil (organic, 1st cold pressing), cream of Soya or rice (cooking)
  • Confectionery: fruit jelly, molasses, agave syrup, fruit jellies, ice-cream (without fruit), meringue. Stewed fruit possible
  • Drinks : all types of water, coffee (in moderation), tea, herbal tea, fruit juice sieved (without fibre), fruit syrup, vegetable broth, sieved and thickened with fine pasta
  • Cook by : steaming, in a court-bouillon, in paper (papillotes), in the oven, in a non-stick frying pan

Food not recommended

  • All « green » vegetables : fresh, raw, cooked , pureed, frozen, dried, tinned or in soups
  • Dried vegetables : lentils, split peas, all dried beans
  • Condiments: gherkins, capers, garlic, onion, shallots
  • Fruit: fresh, frozen, preserved, raw, cooked, candied or in syrup. Oleaginous plants: walnuts, almonds, peanuts, avocados … Jams, honey, marmalades… all desserts containing fruit: tarts, ice creams and sorbets with pieces of fruit, cakes with currants/raisins or other fruit, but also chocolate with hazelnuts, almonds….
  • All cereals and their by-products:  whole breads, complete rice and pastas, whole wheat flours, oat flakes, puffed cereal, muesli … All wholegrain enriched products: bread, melba toast, powders, tablets …
  • Highly mineralised and gaseous mineral waters: Hépar, Contrex, Vichy St Yorre

Highly advised against: coffee and energising drinks

  • Caffeine: stimulates, awakens, increases attentiveness but …
    • Secretion of gastric acid +++ (gastric related burns and pain)
    • increases intestinal motor function (avoid drinking coffee during the race or gels containing caffeine = risk of diarrhoea)
    • increases anxiety and stress (accelerates cardiac rate,  palpitations, digestive problems)
  • Energising drinks : they are unsuitable for  physical effort (acidity rate +++, hyper concentration), favouring the appearance of TD
  • Warm-up drinks: extreme caution  is recommended with the dosage / dilution of sugars and among these last ones  fructose

VI - Competition: nutritional strategy during the race


Plan to take contention sleeves and clothes adapted to outside temperatures. In the case of prolonged stops, change of T-shirt because perspiration on the T-shirt cools which can have repercussions on bowel movements.


  • Nothing new during the race. Always test during training beforehand ‘effort’ drinks, gels, and any solid food which you will eat the day of the race
  • It is recommended that you train your digestive system, that is to say test and train  digestive capacities during long effort, by running  long  sessions with a full stomach, or by reducing to a minimal level the energy contribution (however be careful to avoid hypo-glycaemia!)
  • Note that liquids are always better absorbed than solids (liquids favour the evacuation of  gastric draining, from where comes the importance of the hydration)


The taking of anti-inflammatory drugs is strongly unadvisable during a race due to their aggressive effect on the digestive mucous membrane and dangers for general health. They are associated with serious dehydration; anti-inflammatory drugs increase the risk of renal insufficiency with rhabdomyolysis (destruction of the muscular cells).
See also page "Self-medication"


  • Attention! Certain foods slow down gastric drainage : fatty liquids/solids or hot and very salty, examples : soup with noodles, pâté, salami, bananas, oranges…( to digest these fruits, allow 1 ¾ to 2 hrs)
  • Take no excess  food at the refreshment posts. Limit the portions which can be unusual, unconsciously, for an "out of order» stomach. Avoid eating too much, drinking too much. Preferential food: bread, cheese, gingerbread, stewed fruit, lemon, apple, Vichy pastilles …
  • Chewing ++ : Do not forget to chew! If the food particles swallowed are superior to 2mm, they can activate a partial or total inhibition of gastric draining. Advice: chew well to facilitate the production of the saliva in particular amylase, a pre-digestive enzyme in sweet food.
  • Refreshment zone : eat calmly and leave the refreshment post by walking peacefully, for several minutes, if possible


  • A major cause of digestive problems because it results hydro-electrolytic imbalance (loss of minerals)
  • Dehydration brings on a strong increase of the body temperature with physical effort, which slows down gastric draining.
  • If you use an “Effort” Drink  with added carbohydrates ( BEAG), help digestive comfort by planning an isotonic drink, that is of the same concentration as the plasma,  neutral pH with presence of sodium, carbohydrates, minerals in the form of citrate and bicarbonates, and vitamins (group B, C and E). Read the nutritional labels,  ask for the manufacturer’s parameters, the “effort” drink  should contain neither artificial aromas, nor aspartame
  • Drink dosage (!): a strong concentration  brakes  gastric draining, dilution is recommended (2 to 3 %= 20 to 30 g/l, dosage in relation to outside temperatures)
  • Recommendations for a home-made “effort” drink: 1 litre of water or tea + juice of 1 lemon, 1 dose of salt (1.2g) + an energy compliment (white sugar lump or other carbohydrates)

VII – General advice

What influences the appearance of  digestive disorders, is stress, the volume of liquid absorbed, the intensity of the race, high % slopes which descend violently and the irrigation of the digestive system, including the blood region in the liver which can be reduced, according to each runner, from 50 % to 80 % (of the advantage for the motor muscles).

  • Watch the volume, the flow of liquids and ingested solids (Caution with refreshments which are too sweet or fatty!)
  • Other factors influencing gastric draining: the descents. Moderate the speed on high % slopes (plan, according to need, micro-breaks). Avoid eating before a long descent. Have recovery breaks after an extensive effort-slope (stride shocks  = violent repercussions on fragile digestive systems)
  • Protect the gastro-intestinal zone from the cold.  If your T-shirt is wet have a change in your rucksack (or at a refreshment post)
  • Gastric and intestinal treatments: Attention! Do not abuse them : Imodium©, charbon belloc ©(capsule), gaviscon©, spasfon©, rennie©, smecta©, citrate de bétaïne© (Hépatotrope)

Hydration strategy, why have one?

  • To limit dehydration (protect the digestive system, maintain long-term muscular performance, reverse fatigue limits…)
  • To limit  the build up of exhaustion (linked to the increase of body temperature)
  • To limit the minerals lost through sweating  (by  regularly hydrating without excess  with drinks adapted to the effort)
  • Do not wait until you are dehydrated to drink. On the contrary, do not drink in excess to catch upon dehydration. On average, drink 1 to 2 mouthfuls every 10 to 15 minutes from the beginning of the race (Hydration can be adapted individually)

After the race  

Disturbances to the body functions are experienced for several days after competition (inflammatory state, digestive problems). Recovery is a period which should not be neglected.

  • If nauseous, wait for 1 hour before eating. Hydrate with a recovery drink of salty soup, a little fizzy drink or cola.
  • Wear recuperation contention sleeves
  • Avoid anti-inflammatory medicines
  • Post race celebrations not advised (calorie abuse, manufactured foods (saturated and Trans fats) and alcohol ingestion)? Impact on digestive system weakened by the race (intestinal hyper permeability and a change to the immune system due to the stress hormones stimulated during the race (17-hydroxycorticosterone, adrenocorticotropin…))
  • Recovery of mineral salts: iron, calcium, magnesium, phosphor, potassium, sodium (choice food: lean meats, fish, eggs, dairy products, starchy foods, vegetables +++)

Battle against stress

In every day life and around competitions:

  • Eat in a quiet, calm atmosphere chew the food well, increase the consumption of vegetables and fresh fruit, hydrate well (water)
  • Opt for  yoga, Relaxation therapy, think about relaxing (work on calm and deep abdominal breathing,)
  • Relax. Say to yourself that: "All that happens is OK "→ to release the tensions when training and in the race. Anxiety = vicious circle of the digestive disorders (possible release of an Allergy to the effort due to the Stress before the race)
  • Start the race carefully (to avoid going too fast (fast departure → amplified oxygen debt arising  from the necessity to manage the speed of the race from the beginning)

Conclusion: live a good Race through the following recommendations

Build–up (prevention)

  • The sportsman’s food and dietetics (both are to be tested beforehand, never anything new on D-day)
  • Treat intestinal hyper-permeability 
  • Synthesis glycogen (carbohydrates stored in the liver and muscle): no excess (no binging on carbos), diet without strict residue (without fibres) or of digestive savings

During the race (strategies)

  • Stress management +++
  • Careful start (« warm-up » digestive system)
  • Anticipate the effects of the descents (" no pain ", descend with flexibility, relax, see a chiropodist for inner soles?)
  • Define your Hydration and Nutrition and then manage it beneficially

"We hope that with this advice for the prevention of digestive disorders, centred particularly on your nutrition and hydration, so that you obtain the comfortable digestion you expected and that you will be able to experience our future races completely, and in enjoyment". Corinne Peirano, dietician-nutritionist and ultrafond runner.
Corinne PEIRANO Dietician-Nutritionist
Sports Nutrition  // Eating disorders

14 rue Christophe Colomb 75008 PARIS
Accès Métro Charles de Gaulle-Etoile ou Georges V
Tel : 01 47 23 47 97 - Email : diet.peirano[at]orange.fr