In general proteins should comprise about 12-15% of the diet and may need to be increased if the individual is on a low calorie diet. Proteins are a secondary component to an athlete's diet. It was once thought that proteins were a source of fuel for energy, but it is now known that proteins contribute very little to energy needs. The energy requirements may increase with injury or in the elderly population, but other than these, there should be no added supplementation of protein to the diet.

Functions of proteins:

Act as enzymes
Structural proteins --hair, nails, tendons
Globular proteins --hemoglobin
Hormones
Acid-Base balance
Muscle contraction --involved with the actin-myosin cross-bridges
Blood clotting --thrombin, fibrin
Antibodies --immunity
Energy source --only if CHO and fats aren't available

Types of protein:

Essential amino acids
* must be supplemented in the diet
Non-Essential amino acids
* can be generated by the body

Classification of proteins:

Complete
* Contain all essential amino acids
* Eggs, milk, cheese
Incomplete
* Lacks one or more of the essential amino acids
* Grains and vegetables
Complementary
* Do not need to be consumed in the same meal
* Corn and peas
* Lentils and breads

Do athletes need more protein than the normal individual?

Maybe some, but not much more than the diet can provide. Two factors that we can look at to determine the answer to this question are protein as an energy source and the amount of protein lost from the body during exercise. We now know that protein is not a significant source of energy during exercise. Protein may be used if the individual is lacking CHO and fats, but this is pretty uncommon. If proteins are not utilized that much for energy, then we don't really need more. Protein losses in the urine and sweat are relatively low. An athlete may lose 3 grams/day in the urine and 1 gram/L of sweat that is released from the body. Since we have intakes that are usually higher than the 12-15%, we do not need to worry about our protein requirement.

The lower the energy intake, the more protein an individual should consume. Along those same lines, if CHO intake is high, protein intake will probably be lower. The strength training athlete may need more protein due to the degradation of muscle proteins during training. Most of the increased need can be met by the diet. The environment that the athlete performs in may also influence protein requirements. A cold environment may use more fat and protein for fuel, compared to CHO being the major source of fuel during warm temperatures.

It should be noted that consuming 12-15% of your diet from protein should fulfill the needs of the athlete.

The Effects of Excess Protein in the diet:

Promotes increase in fat intake and lower CHO intake
May lead to dehydration
May tax the kidneys and liver
Increase calcium excretion
Increase risk of gout
Will not increase muscle strength or endurance

The extra protein that is added to the diet will can be used as energy or will be stored as fat. The only time a high protein diet is safe is during time of healing from an injury or surgery or when an individual has a low caloric diet.