Soy Protein, a High-Quality Protein

The Role of Protein

Proteins and their component parts, amino acids, serve as building blocks for synthesis of proteins into skeletal muscle. Muscles need protein to repair, rebuild and grow.

In order to promote increases in muscle size (hypertrophy) and increase in strength, it is an absolute requirement that athletes be in a positive nitrogen status. Nitrogen status is determined by measuring dietary nitrogen intake (protein is 16%) and subtracting nitrogen loss (urine, sweat, feces).

A debated question for over 100 years is whether large quantities of dietary protein are necessary to optimize protein synthesis and enhance muscular hypertrophy and strength. The current recommended daily allowance (RDA) for protein for sedentary people is 0.8 grams per kilogram body weight. This is equivalent to 50 to 60 grams of protein for a 165 lbs. athlete. Exercising individuals may need more protein, up to is 2.0 grams per kilogram body weight. However it is important to know that the RDA for protein was derived from both short- and long-term nitrogen balance studies from subjects whose lifestyles were essentially sedentary.

This RDA for protein needs to be increased if you are involved in more strenuous activity.

Protein Quality

As important as the daily amount of protein consumed, the source and quality of protein is key. Food proteins are often classified as being either complete or incomplete depending on their amino acid content. Complete proteins are those food proteins that contain all nine indispensable amino acids in concentrations sufficient to meet effectively the requirements of humans.

In January 1993, the U.S. Food and Drug Administration (FDA) replaced the Protein Efficiency Ratio with Protein Digestibility Corrected Amino Acid Score in food labeling. The agency adopted this new, and potentially more accurate method of evaluating protein quality as the standard by which the percent Daily Value (%DV) of protein is calculated for food labels. The PDCAAS is currently used for labeling protein on food products for adults and for children over one year of age.

Using the PDCAAS method to evaluate protein quality has shown that some isolated soy proteins are also complete proteins; that is, they provide all the indispensable amino acids in sufficient quantity to meet the needs of humans.

The PDCAAS of Solae™ soy protein is 1.0, which is the higest score that a protein can have. Solae™ soy protein is equal in protein quality to meat, milk and egg protein. It meets or exceeds the essential amino acid requirements of children and adults.

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Arginine / Glutamine / Critical Cluster

Solae™ soy protein boasts the highest concentration of amino acids in what is referred to as the "critical cluster". Included in this critical cluster of aminos are the three Branched Chain Amino Acids, BCAAs (Leucine, Isoleucine and Valine), and glutamine and arginine.

Glutamine and Arginine are conditionally essential during physiological stress (training), and both enhance the immune system. Additionally, Arginine promotes anabolic (building) activity that results in muscle formation while Glutamine buffers lactic acid buildup to reduce fatigue.

Arginine plays a key role in stimulating release of anabolic hormones that promote muscle formation. Arginine is recognized as a semi-essential amino acid for good health although it is readily synthesized from ornithine. Because it enhances wound healing and has an immuno-enhancing effect, many investigators consider arginine to be a "conditionally-essential amino acid" in the stressed state. Arginine serves as a vehicle for transport, storage and excretion of nitrogen. Arginine is the precursor of creatine phosphate, one of the most important sources of cellular energy in muscle. Recently, arginine was shown to be the unique substrate for the production of the biological effector nitric oxide. This important pathway is present in many tissues and cells including endothelium, brain and inflammatory cells. Studies show that arginine has a pharmacologic action that may account for some of the anabolic activities and improvement in immune function observed in animals and humans who have received diets supplemented with arginine. For athletes, arginine may play a key role in muscle formation, reduction of physiological stress, blood vessel health and in helping to maintain a strong and healthy immune system.

Glutamine is an amino acid that is considered essential during metabolic stress. Glutamine enhances nitrogen balance, promotes protein synthesis, and improves immune function. It serves as the main energy source for the intestinal epithelium and helps maintain gut mucosa integrity. Glutamine serves as a precursor to glutathione, and as such has antioxidant effects by increasing intracellular glutathione content. Even more important for the athlete, glutamine helps to maintain cellular hydration and buffers lactic acid build-up that occurs during exercise. These functions of glutamine help to support performance and recovery.

The branched chain amino acids leucine, isoleucine and valine are used as an energy source during exercise . In the first 20 minutes of moderate to intense exercise, muscle glycogen is used as the primary energy source and provides glucose for muscle fueling. After this initial 20 minute phase of exercise, fatty acids and the branched chain amino acids are used as major energy sources. The BCAA have an increased uptake by muscles yet not by the liver and have an increased rate of oxidation during exercise. During endurance activity, nitrogen is removed from the branched chain amino acids and converted to alanine. Alanine is transported from the muscle to the liver via the bloodstream where it is converted to glucose. Glucose from the liver returns to the muscle to supply energy for fueling and power performance. Researchers continue to evaluate the efficacy of the branched chain amino acids for reduction of central nervous system fatigue as well as their use for the enhancement of immune system function.

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