Proteins are indispensable to the functioning of the body. They are the essential nourishment needed to build the muscles which are key to all its physical activity. Their other uses also include cell synthesis, antibody manufacture, hormone production and they enable the transfer of oxygen.
The proteins in the athlete's body
The body of an average sized adult contains between 10 and 12 kg of protein located principally in the muscles.
Protein molecules are made up of a combination of amino acids. One can suggest an analogy between amino acids and the alphabet, proteins can be compared to words containing hundreds of letters - in this case amino acids. A protein is made up of at least 100 amino acids.
Nine of these amino acids absolutely must feature in our diet because the body cannot manufacture them. These nine amino acids are called "essential amino acids".
The biological properties of a protein therefore depend in the sequence of amino acids of which it is composed.
Differences in protein quality
Proteins high in biological value (or complete proteins) are provided by foods which contain all the essential amino acids both in quantity and in sufficient proportion to enable the growth and repair of tissues. If one or several essential amino acids are lacking,the proteins produced will be incomplete or low in biological value.
Sources of Protein
Foods containing complete proteins are: eggs, milk, meat, fish, poultry. Of these foods, eggs provide the optimal mix of essential amino acids. They represent the highest biological value equal to 100.
The role of proteins in the athlete's body
The main role of proteins taken in from food is the supply of amino acids for the various anabolic reactions within the body.
The three principal sources of protein in the body are the muscles, the visceral tissue and blood plasma. Proteins contribute to the structure of tissue and are used as constituent elements of metabolism and the hormonal system.
Dietary Reference Intake (DRI) of proteins
For leisure sports, the daily protein intake recommended is 0.8 to 1.1g per kg (of body weight).
For endurance sports, the daily protein requirement increases slightly and is between 1 to 1.2g per kg.
For strength sports, the daily protein requirement is between 1.3 and 1.5g per kg when the objective is muscular fitness, increasing when weight gain is in view (2g per kg daily). In this case, standard food intake is reinforced with protein supplements such as casein based or whey protein powders.