Nutritional needs of the athlete

A healthy diet, adequate to the specific nutritional requirements of the athlete, will help him/her to support any scientifically conceived training program, to keep fit or to compete; it will contribute to promote a better adaptation to the training stimulus and will reduce the risks of suffering injuries or diseases that will have repercussions in the athlete's active life and/or in later stages of his/her life.

The nutritional needs of athletes vary depending on sport, gender, body composition and other aspects. Even the diets provided to the same athlete, in situations of competition, training or active vacations, are different and are also modified throughout their sporting life, adapting to competitive results, and variations in physical performance, among other factors that change over the years.

Energy needs

The energy needs of athletes in general are very high, taking into account that during one hour of intense physical activity a top level athlete can consume between 500 and 1000 kilocalories. For example, a soccer player weighing 75 kilograms, during a full game, may need about 1600 kilocalories.

The extra amounts of energy to cope with extremely high levels of physical activity should come from increased intakes of carbohydrates rather than fats and proteins.

It is recommended that the percentage of calories supplied by proteins, fats and carbohydrates, with respect to the total energy consumed in the diet, should be as follows:

• Carbohydrates should guarantee between 55 and 60% of the total calories provided by the diet; and in some short periods (of approximately one week), close to competitions, they can reach up to 70%.

• Lipids or fats should contribute around 30% of the total calories provided by the diet.

• Proteins should contribute between 10 and 15% of the total calories contributed by the diet.

Carbohydrate requirements

In the organism, carbohydrates are stored in the muscle and liver in the form of glycogen; this constitutes the most rapidly available source of energy; however, the storage capacities are small and therefore, the possibilities of depletion and fatigue are very high, if no external energy supply is provided during prolonged physical effort. Glycogen stored in muscle and liver has the following functions:

• Glycogen stored in the liver: maintains blood glucose concentration; glucose constitutes the only source of energy used by the brain, so its levels must be adequate throughout training or competition, to achieve concentration and good mood of the athlete.

• Glycogen stored in the muscle: it must supply the energy needs of the muscle to perform the sports activity. Glycogen is the only energy source that can be metabolized both in the presence of oxygen (aerobically) and without the presence of oxygen (anaerobically); fats and proteins only do so in the presence of oxygen.

During short, high-intensity sporting events, such as sprinting, jumping and throwing, which require anaerobic sources of energy, muscle glycogen is used, whereas aerobic sources of carbohydrates and fats are used in longer, lower-intensity events, such as marathons. In events such as soccer and basketball, in which there are periods of high intensity and others of lower intensity, the body uses both aerobic and anaerobic sources of energy.

The recommended amounts of carbohydrates depend on total energy expenditure, gender, type of sport and environmental conditions; generally, for a daily moderate intensity training of one hour duration, 3 to 7 grams per kilogram of body weight per day; and 7 to 12 grams per kilogram of body weight per day during endurance training.

Most of the carbohydrates included in the athlete's diet should be complex: brown rice, whole-grain pasta, potatoes, sweet potatoes, whole-grain bread and legumes. The simple carbohydrates recommended are fruits and dairy products, which provide numerous nutrients in addition to energy.

Fat requirements

Fats are less energetically profitable than carbohydrates, this means that the organism to obtain a certain level of energy using fats as fuel, must invest more energies than those that you need, if it would use carbohydrates as fuel. However, the body has a greater availability of fats, since they can be stored in greater quantities. The energy from fats is used once the energy from carbohydrates has been used up, so they are the fuel required for long endurance events.

Fat intake should represent about 30% of the total energy provided by the diet, although in endurance sports it can be as high as 35%. When the energy intake of fats exceeds 35%, the energy contribution of carbohydrates and/or proteins deteriorates, causing a reduction in sports performance and endangering the athlete's health in the short, medium and long term. If, on the other hand, fat intakes are not sufficient, symptoms of deficiencies of fat-soluble vitamins (a, d, e, k) and fatty acids may occur, also causing serious health problems for the athlete.

It is recommended that the contribution is obtained from the different types of fats in the following proportions:

• Between 15% and 20% of monounsaturated fatty acids, coming mainly from the use of olive oil.

• Between 7% and 8% of saturated fatty acids, coming from whole milk, butter, fatty meats, etc. It is necessary to control that the high intakes of meat that athletes tend to consume, do not contain fats, to avoid the overconsumption of saturated fats.

• Between 7% and 8% of polyunsaturated fatty acids come mainly from oily fish, nuts and seed oils, such as sunflower, corn and soybean. The consumption of these fatty acids (especially omega-3) is associated with increased oxygen delivery to the muscles, increased performance, accelerated recovery, and reduced joint stiffness and inflammation.

Protein requirements

Athletes have higher protein requirements than ordinary people; increases should compensate for the increased muscle degradation that takes place as a consequence of intense exercise, and contribute to the growth of muscle mass, as proteins are involved in muscle formation.

Between 1.2 and 1.7 grams of protein per kilogram of body weight per day are recommended, which is considerably higher than the recommended intake for a sedentary person, which is 0.75 grams of protein per kilogram of body weight per day. It is warned that protein intake should be distributed throughout the day, ingesting between 20 and 25 grams of protein with each main meal and also immediately after physical activity is concluded.

Experts warn that to promote muscle repair and growth it is not necessary to eat more protein than recommended, since what causes muscle growth is the stimulation of muscle tissue through exercise and not additional protein.

The excessive consumption of proteins is harmful for the athlete, since it generates a greater production of urea and non-metabolizable acids that the organism needs to eliminate through urine, contributing to dehydration and forcing the work of the renal apparatus. It could also increase urinary calcium losses and favor bone demineralization.

Vitamin and mineral needs

Although intense physical activity requires a greater supply of vitamins and minerals, increased caloric intake, as long as it is carried out following a varied and balanced diet, will provide the necessary micronutrients. The effects of vitamins and minerals in the organism are superior when they are obtained from a diet rich in fruits, vegetables, whole grains, legumes, unsaturated oils, fish, dairy products and lean meats.

Studies carried out on top level soccer players show that most of them can obtain the recommended intake of vitamins and minerals through daily meals; and that the reasons why some of them are not able to obtain the required amounts of micronutrients from the diet are the following:

• Restrictions of energy intakes for prolonged periods of time in order to reduce body weight.

• Following diets with little variety, rich in foods that are not very nutritious.

In cases of vitamin and mineral deficiencies, sports nutrition specialists justify the use of supplements under expert supervision.

The micronutrients that should be given more attention are the following:

• Iron.

• Calcium.

• Zinc.

• Magnesium.

• Group B vitamins.

• Antioxidant vitamins and minerals such as vitamin c, e, ß-carotene and selenium.

Iron: Iron deficiency in the athlete can cause reductions in the athlete's aerobic capacity, a decrease in his physical performance and other disorders for his general health. Iron deficiencies can occur for the following reasons:

• Increased synthesis of hemoglobin and myoglobin, iron-containing blood and muscle proteins.

• Decreased absorption.

• Increased elimination through sweat.

• Possible gastrointestinal blood losses.

In cases of iron deficiencies in athletes, it is necessary to periodically monitor serum iron levels in order to detect possible deficiencies; if deficiencies exist, they can be treated with appropriate nutritional intervention and, if necessary, with supplementation.

Calcium: it is the most abundant mineral in the body, forming part of bones and teeth. It plays an important role in the formation and maintenance of bone tissue and, together with potassium and sodium, regulates muscle concentration.

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