Nutrition for triathlete

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Nutrition for triathlete


  • Any physical effort uses energy. This energy is supplied by food and stored in the body (in the blood, liver and muscles). The quality and quantity of reserves stored governs the body's capacity to sustain a long effort.
  • Digesting the food you have eaten uses energy and causes more blood to flow into the digestive system, so performances are lower during the digestive process. The length of this period depends on the amount and, in particular, quality of the food.
  • In the course of some efforts, the body suffers minor lesions which heal more quickly with suitable nutrition.
  • Deficiencies in some nutrients can lead to serious illnesses and it is, therefore, essential to have a balanced diet.
  • The weight of triathletes may be modified by the quality and, especially, the quantity of food they eat. Any unnecessary weight loss results in a reduction in strength and, thus, in performance. Putting on superfluous weight results in a drop in performances owing to the excess weight to be carried.

The various nutrients:


  • Proteins are nitrogen-based substances containing amino acids.
  • Amino acids are the main constituents of muscle tissue and some hormones (such as EPO and growth hormone).
  • The main sources of proteins are: eggs, meat, fish and dairy products. Significant quantities are also provided by cereals, and leguminous and other starchy plants. Animal proteins, however, have a higher biological value as they contain more essential amino acids.
  • The proteins consumed should be between 10 and 15% of the total calorie intake.
  • Protein deficiency results in the loss of muscle mass.
  • A surplus of proteins slows down digestion and produces waste in the blood.


  • Fats, or lipids, are mainly found in butter, oils, pastry, meat, eggs, cheese, fish, walnuts, almonds, hazelnuts, avocado and olives. They are a constituent of cell membranes and the precursors for some hormones (such as testosterone).
  • Fats contain a lot of calories. They are therefore an efficient fuel for long training sessions and for races of the Ironman type. They are, however, difficult to use and are not suitable for high-intensity efforts.
  • Some fat is synthesised in the human body from excess glycogen, but essential fatty acids have to be obtained from food.
  • There are three types of fatty acids: saturates which increase the level of "bad" cholesterol in the blood, mono-unsaturates which increase the level of "good" cholesterol in the blood and polyunsaturates which reduce the total cholesterol level.
  • The consumption of fats should represent 25 to 30% of the total calorie intake.


  • Carbohydrates are either simple or complex.
  • Simple carbohydrates, such as sugars, have a short-term effect, quickly releasing energy but are burned up quickly. They are useful to get an energy boost during a demanding effort. But beware of reactive hypoglycaemia: the body reacts against the absorption of glucose by producing insulin which causes a drop in blood sugar level. Simple sugars must be consumed with moderation.
  • Complex carbohydrates take longer to break down and provide energy on a regular, longer-term basis. They produce little waste during long-term efforts.
  • the advantages of complex carbohydrates and should be consumed instead of glucose whenever possible.
  • Carbohydrates are found in: pastry, honey, jam, sweet beverages, confectionary and fruit (simple carbohydrates), and bread, pasta, rice, potatoes, flour and pulses (complex carbohydrates).
  • The consumption of carbohydrates should represent 60 to 65% of the total calorie intake, less than 10% of which should be simple carbohydrates.


  • Sodium (Na) is a vital component of the blood. Much of it is lost in perspiration and it is, therefore, important to take sufficient sodium during very long efforts (Ironman). A normal diet easily contains enough.
  • Potassium (K) is a major component of cells. It plays an essential role in glycogen metabolism. A lot of potassium is lost in the course of efforts. If you take in enough after an effort, by eating bananas, dried fruit and nuts, walnuts or almonds, this makes it easier to store glycogen and thus facilitate recovery.
  • Calcium (Ca) and phosphorus (P) are essential constituents of bones. A calcium deficiency weakens bones and increases the risks of stress fractures. Needs can be covered by daily consumption of sufficient quantities of dairy products.
  • Magnesium (Mg) plays a fundamental part in many reactions, including storing and using glycogen. Magnesium-rich foods include cocoa, walnuts, hazelnuts, peanuts, almonds, shellfish, green vegetables and wholemeal cereals.
  • Iron (Fe) is used to carry oxygen from the lungs to the muscles. Iron deficiency is common, so you should make sure your iron intake is sufficient. The best iron sources are: red meat, shellfish, liver, bean sprouts, soya flour, spirulina and black pudding. Iron is easier to assimilate if you take vitamin C at the same time as iron-rich food.


  • Micronutrients are trace elements found in the body. They are essential for healthy functioning of the body. They can, however, be toxic at high doses.
  • Zinc (Zn) is a component of many enzymes and, among other things, plays an important part in the immune system and contributes to speedy healing. Good sources of zinc are oysters, liver, wheat germ, cheese, cocoa, meat and peanuts.
  • Chromium (Cr) helps in the working of insulin, the synthesis of glycogen and the utilisation of amino acids. It is found in brewer's yeast, wheat germ, liver and wholemeal cereals.
  • Copper (Cu) favours the assimilation of iron and fat metabolism. Liver, seafood, soya and pulses are good sources of copper.
  • Selenium (Se) is an antioxidant that is present, in non-negligible quantities, in seafood, liver, wheat germ and brewer's yeast.
  • Manganese (Mn) is mainly found in cereals and green vegetables. It plays a part in the development of bones and some enzymes.


  • Vitamins are essential for a healthy body. They are not synthesised in the human body and must therefore be provided in the diet.
  • There are 13 vitamins: A, D, E, K (which are liposoluble), C, B1, B2, B5, B6, B12, PP (or B3), folic acid (or B8) and biotin (or B8).
  • Vitamin A plays an important part in eyesight, growth, and the regeneration of skin and mucous membranes. It is found mainly in liver, egg yolk, milk fat and some vegetables (carrots and spinach).
  • Vitamin D is essential for bone growth and regeneration. It is mainly found in oily fish, liver, egg yolk and milk fat.
  • Vitamin E is an antioxidant. It is mainly found in vegetable oils, cereal germs, green vegetables, eggs, walnuts and avocados.
  • Vitamin K is indispensable for blood clotting. It is mainly found in green vegetables, liver and eggs.
  • Vitamin C boosts the immune system and facilitates the absorption of iron and cell synthesis. It is mainly found in fresh fruit and vegetables.
  • Vitamins in the B group are important for the proper working of nerves and muscles as well as for the utilisation of carbohydrates, fats and proteins. They are mainly found in meat, fish, eggs, dairy products, wholemeal cereals and leguminous vegetables.

Basic rules for a good diet:

  • Water is the main component of the human body, so it is essential to drink plenty - especially of water - between meals, in particular, even when you do not feel thirsty.
  • Each time you eat food, this is followed by digestion which uses energy and causes blood to flow towards the digestive system. This temporarily decreases performances, so you should take care not to eat just before making an effort, unless you eat only very easily digestible food.
  • Any food that is eaten to excess will be burned up as the result of unnecessary energy expenditure or stored which means putting on unnecessary weight.
  • Deficiencies of some substances have harmful effects, such as loss of muscle mass, weakening of the immune system, tiredness and, even, serious illness.
  • It is important to have a varied, balanced diet that is rich in essential nutrients in order to avoid any risk of deficiencies.
  • It is advisable to eat easily digestible food in order to avoid the weakening effects of difficult digestion.
  • Carbohydrates can be eaten immediately after an effort to facilitate the recovery of energy reserves.
  • Carbohydrates can be taken in liquid form during an effort in order to help you keep going.

The "ideal" diet:

  • Replace glucose with fructose and take unprocessed foods instead of refined foods whenever possible.
  • To be eaten daily: wheat germ, brewer's yeast, dairy products, fruit and fresh vegetables.
  • To be eaten once a week: shellfish, liver and red meat.
  • To be eaten several times a week: pulses, potatoes and oleaginous fruits (walnuts, hazelnuts, almonds, etc.).
  • Eat 3 or 4 proper meals a day.
  • Let yourself go, from time to time, by eating your favourite foods.

Dissociated diet:

  • The aim of the dissociated diet is to increase glycogen reserves for an important race.
  • This is based on the following guidelines: Monday, Tuesday and Wednesday: low-carbohydrate food; Thursday morning: intensive training on empty stomach to use up glycogen reserves as much as possible; immediately afterwards and through to the end of the week: hyper-carbohydrate food and very light training; Sunday; race day.
  • This type of diet is extremely tough and should be reserved for major competitions (2 or 3 times a year at most) in order to avoid deficiencies and hormonal problems.

Training on empty stomach:

  • The aim of training on an empty stomach is to force your body to tap into its energy reserves which, in the longer term, increases those reserves and improves muscle efficiency.
  • Training sessions on an empty stomach should preferably be performed at a slow rate and should last long enough for your body's energy reserves to be almost exhausted.
  • This type of training is extremely effective to improve endurance as it forces the body to use fats for energy. Your body's use of fats can be further enhanced by taking L-Carnitine and by taking one or two spoonfuls of oil before starting.
  • Training sessions on an empty stomach must not be performed too often as they are extremely demanding and increase the risks of deficiencies of various nutrients. These risks can be reduced by taking a low-energy drink that is rich in minerals before the training session.
  • It is important to eat plenty immediately after the training session in order to recover your energy reserves more quickly. During training sessions of this kind, you should drink water only.

Dietary supplements:

  • Dietary supplements are not indispensable for athletes with a rich, balanced diet. Some supplements do provide benefits, however. Brewer's yeast and wheat germs are both very rich in essential nutrients and can help if you take a little every day.
  • Magnesium deficiencies are common and cause serious tiredness. Magnesium supplements are often useful for many athletes.
  • Branched-chain amino acids (BCAA) are provided in sufficient quantities by a protein-rich diet. However, given the fact that proteins are relatively difficult to digest and the importance of BCAAs for athletes, it is often useful to take BCAA supplements.
  • Iron deficiencies have disastrous consequences for the body and, therefore, on performance. It is probably a good idea to take supplements if you are a vegetarian, a woman or going through a very tough training phase.
  • Vitamins are almost always eaten in sufficient quantities in a proper diet. It can, however, be useful to take vitamin supplements if you do not eat much fresh fruit and vegetables.
  • If you have any doubts about the need to take other supplements, it is advisable to see a specialist (doctor or dietician) who can recommend a solution specifically for your case.


  • A healthy diet is very important for endurance athletes as it helps to make training more effective.
  • Heavy training schedules increase your requirements for many essential nutrients, so make sure your diet is sufficient and well balanced.

Le site Mission Triathlon est la disposition de tous les triathlètes souhaitant optimiser leur préparation au triathlon. Vous y trouverez des conseils comme la technique de natation pour le triathlon, la technique de vélo pour le triathlon, technique de course à pied pour le triathlon, l'alimentation pour le triathlon ou la musculation pour le triathlon. Vous pouvez aussi utiliser gratuitement le carnet d'entraînement online ou demander un devis pour un programme d'entraînement de triathlon personnalisé.