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Proteins

Proteins are a secondary component to an athlete's diet.  Proteins should comprise about 12-15% of the diet, and may need to be increased if the individual is on a low calorie 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.

The functions of proteins in the body are:

     1.  Act as enzymes

     2.  Structural proteins --hair, nails, tendons

     3.  Globular proteins --hemoglobbin

     4.  Hormones

     5.  Acid-Base balance

     6.  Muscle contraction --involved with the actin-myosin cross-bridges

     7.  Blood clotting --thrombin, fibrin

     8.  Antibodies --immunity

     9.  Energy source --only if CHO and fats aren't available; won't happen too frequently

The two types of protein are:

  1.  Essential amino acids

  2.  Non-Essential amino acids

***Amino acids are the building blocks of proteins.***

The classification of proteins are:

 1.  Complete

 2.  Incomplete

 3.  Complementary

Do athlete's 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 exericse.  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.  It is a common misconception that to build more muscle you need to have more protein.  This may not be the case.  There are a few exceptions that might be noted and we will discuss them next.

Variables in Determining Protein Needs:

     1.  Energy intake

     2.  CHO intake

     3.  Type, frequency, and duration of exercise

     4.  Degree of fitness

     5.  Ambient temperatures

     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.  If CHO intake is low, protein intake will probably be higher.  The type of exercise may influence how much the athlete needs.  If an athlete is trained, they may burn more protein than an untrained individual.  An endurance athlete may need more than a strength training athlete.  The endurance runner has an increased need for mitochondrial proteins.  They also may spare CHO utilization and use more protein for energy during exercise.  This would allow them to perform better during prolonged activity.  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, especially since Americans already consume more than enough protein in their diets.  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.

***The RDA for protein is 0.8 grams/kg of body weight.

***The ADA for protein is 1.0 grams/kg of body weight.

Lemon stated in Sports Nutrition for the 90's that endurance athletes may need 1.2-1.4 grams/kg of body weight and a strength   training athlete may need 1.2-1.7 grams/kg of body weight.

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:

     1.  May lead to dehydration

     2.  Promotes increase in fat intake and lower CHO intake

     3.  May tax the kidneys and liver

     4.  Increase calcium excretion

     5.  Increase risk of gout

     6.  Will not increase muscle strength or endurance --do need a little extra if exercising, but not an abundance

***The extra protein that is added to the diet will can be used as energy or will be stored as fat.***

The Way to Build Muscles:

     1.  Exercise and strength train with weights

     2.  Have a diet high in CHO so you can spare the protein to help build muscle

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.  Studies show that taking amino acids supplements do not work.  They are expensive and unpalatable.  They may even cause gastrointestinal upset.  Amino acid supplements have little value to the athlete.

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