For endurance performances, it is better to avoid a high-fat diet or to keep its share at a maximum of 25 percent. The energy yield per litre of oxygen is very low, which means that the effort required to obtain the energy is quite high. Furthermore, the digestion of fats is tedious and the overall endurance performance is reduced.
Fats are only used more intensively when the energy requirement exceeds 5000 kcal. With such an enormous energy requirement, the amount of food would simply become too large if fats were not used. Especially oils with polyunsaturated fatty acids and milk are excellent sources of fat. The fat content of milk in particular can be broken down quickly in the intestine, so that the fatty acids are quickly absorbed through the intestinal wall.
When it comes to protein intake, an endurance athlete does not usually have to be so consistent in his or her attention to what and how much food he or she eats. Since the total amount of food is increased, the protein content of the diet is also increased and there should be no problems with its supply. Especially with eggs, milk and meat in the total food intake, the need for protein is more than covered.
With vitamins it is similar to the situation with proteins. It has become generally accepted opinion that the increased food requirement also provides for an increased vitamin supply and that this is sufficient for the endurance athlete. The prerequisite for this, however, is a complete diet, without any renunciation.
The vitamins A, E, K and D are definitely well covered by the diet. A slight deficiency of the vitamins of the so-called B group, especially vitamins B1 and B2, which ensure effective carbohydrate breakdown, may occur under certain circumstances. In this case, external vitamin supply should be used.
Many athletes take additional vitamin supplements and hope that this will improve their performance. This usually does not occur. An increase in performance after taking vitamin preparations is usually due to a previous deficiency. Only with a high intake of vitamin A and D can pathological symptoms occur.
Iron is an important mineral for endurance athletes, which should always be available in sufficient quantities in the diet and body. Only five to ten percent of the iron supplied is absorbed by the intestinal wall. Especially female endurance athletes often suffer from iron deficiency anaemia. This reduced endurance performance, which is associated with fatigue and listlessness, can be due to a haemoglobin deficiency caused by an iron deficiency.
Water, nutrient and electrolyte losses
During long endurance events such as a marathon, athletes sweat two to four liters at a temperature below 20° Celsius in order to conduct the heat generated by the muscle work out of the body. The body therefore loses a lot of water and thus also electrolytes and nutrients. If these considerable water and nutrient losses are not replenished, the athlete’s performance will directly decrease.
Even water losses of two to five percent of the body weight slow down the heartbeat and thus reduce the total time that can be spent on endurance performance. Water and electrolyte losses during competition must therefore be monitored and replenished at all times. Water is very important for the body as it has a transport, dissolving and thermoregulatory function and is therefore irreplaceable.