There is still confusion and controversy over protein requirements for athletesparticularly for those involved in intensive training. Even scientists disagree on exact protein requirements, and so much strength and conditioning professionals who wish to improve their muscular athletes have their protein intake beyond the recommended daily allowance (RDA). Much of the confusion arises from poorly designed studies and a lack of understanding of protein metabolism, resulting in recommendations that are unnecessary and sometimes harmful. Proteins are complex molecules that many enzymatic and structural functions related to the promotion of body growth, maintenance and repair. The function of the protein in the diet of the athlete, sports enthusiast or a sedentary person of the amino acids necessary for the body to contribute to the protein of skeletal structures (including muscles include assimilation) and hormones, function as receptors the cell membrane and maintain fluid balance. Protein, which contributes 4 calories per gram, also makes a small contribution (~ 5.10%) to produce energy, but this offer may increase during periods of reduced power consumption. The fundamental building blocks of proteins are amino acids that contain nitrogen. State of nitrogen the body can be determined by measuring the nitrogen intake in the diet (via protein intake) and subtracting nitrogen loss (sweat, urine and faeces). The measurement of nitrogen balance in the body provides an estimate of the total protein balance of muscle protein, because a person is in a constant state of turnover. For example, reduced protein synthesis allows catabolic (breakdown) effects predominate, resulting in an increased excretion of nitrogen. When protein is taken in large quantities, can be oxidized for energy or converted into fat. Therefore, the protein in muscle is largely determined by the balance between a positive nitrogen balance, which promotes protein anabolism (growth or accumulation), and a negative nitrogen balance, which promotes catabolism. Quality protein is an important factor in determining the daily needs. Of the 22 amino acids necessary for protein synthesis, 9 are essential and 13 nonessential. The essential amino acids that the body can not synthesize and therefore must be obtained from the diet. No essential amino acids, provided that there is an adequate source of nitrogen synthesized in the body, but can also be obtained from the diet. People must get enough essential amino acids for proper protein synthesis of human tissue. Dietary protein contains all essential amino acids, are known as proteins, and comes mainly from meat, fish and dairy products. Incomplete proteins lack one or more of the essential amino acids are the components of these plant foods like nuts, grains and legumes. Consequently, this means the need for a balanced diet with a variety of foods rich in protein. It also appears that vegetarians may be deficient in one or more essential amino acids and may thus benefit from protein supplements.