Written by Amy Kosowski, M.S., LDN. A review of the various types of protein used by atheletes.

Athletic competition is at an all time high and athletes are looking towards dietary supplementation in order to get a competitive edge. There are many high-quality sports supplements products available today and the most popular of these is protein supplements. Informed consumers are aware that fulfilling protein requirements is one of the most critical factors for the enhancement of athletic performance. However, with the number and variety of protein supplements available, it can be difficult to choose the appropriate product for individual needs.

Protein is the second most plentiful substance in the human body next to water. It is also the major building block for the production and maintenance of muscles, blood, hair, skin, nails, internal organs and our brain. During the digestion process, large protein molecules are broken down into simpler components called amino acids. The body requires twenty-two amino acids to generate the proteins needed to maintain cellular processes. The body itself can produce fourteen of these twenty-two amino acids; the remaining eight must be supplied by our diets. The eight amino acids that our body cannot produce are called “essential amino acids”.

The quality of any protein source is determined by its amino acid content. Foods that contain all eight essential amino acids are termed “complete protein” sources. Protein obtained form animal sources has complete protein, whereas protein obtained from plant sources is generally incomplete protein. The exception to this rule is soy, which is the only vegetable source of complete protein. Quality is often rated by its “Protein Efficiency Ratio” or PER. The PER rating measures the ability of a specific protein source to support growth in young animals. Higher quality sources will maximize the growth and overall health of the animals. Therefore, as the quality of the dietary protein increases, the PER rating of a particular source is increased.

The most efficient way for athletes to increase their protein intake and fulfill their requirements is to add protein supplements to a daily meal regimen. There are many different types of protein supplements available, and some have specific advantages over others depending on ultimate or short-term goal of the user. For example, one type of protein may best utilized after a workout, while another may be better used as a meal replacement late in the day. The most common forms of protein supplements currently consumed by athletes are whey, casein and soy.

Whey is a protein derived from milk. Whey protein concentrates are produced from liquid whey by these processes- clarification, ultrafiltration, diafiltration, and drying. There are three main attributes of whey protein that makes it an ideal supplement for athletes. First, whey protein is a very high quality protein with a high PER. Second, whey is one of the richest sources of Branch Chain Amino Acids (BCAAs). BCAAs are unique in their ability to be used during strenuous exercise as an energy source, thus inhibiting muscle catabolism (1). Finally, whey protein is rapidly digested and assimilated by the body (2). Therefore, whey protein is an ideal post-workout supplement as it quickly provides replenishment for muscle tissue and BCAAs lost during exercise. Because it is so rapidly taken up by muscle cells, however, whey protein does not provide a continuous, long-lasting flow of amino acids to feed muscle tissue.

Another reputable protein in the sports supplement industry is casein. Casein contains all of the essential amino acids and is an excellent form of protein. Caseinates are produced from skim milk through a processing technique that separates the whey from the casein, which is then resolubilized* and dried. Casein is a high quality, inexpensive protein that is slowly digested (2). Its PER is only slightly lower than that of whey. One of the main advantages of casein protein is that it contains more glutamine and tyrosine than any other protein. Casein is also remarkably effective in preventing muscle catabolism (3). Many athletes consume casein protein before retiring in the evening because it provides a steady flow of amino acids to the body throughout the night. The main disadvantage of casein is that although most people can tolerate it, casein is a common allergen.

Soy protein is another very popular protein source amongst athletes. Soy protein is a complete vegetarian source, although it is somewhat low in the essential amino acid methionine. It is obtained from soybeans through a process of water extraction, precipitation, washing and drying. Soy provides more of the “critical cluster” (BCAAs, Glutamine, Arginine) amino acids than any other protein. Soy protein, therefore, helps build and maintain muscle mass and lean body tissue (4). In addition, soy exerts potent antioxidant effects, perhaps counteracting exercise-induced oxidant stress (5). Soy digests more slowly than whey providing the body with a steadier release of protein after ingestion (6). The Protein Efficiency Ratio (PER) of soy protein is similar to dietary meat or fish and slightly lower than egg, milk, casein and whey.

After considering the benefits of each type of protein, it is challenging to pick one as the clear-cut winner. Because each of these has a number of benefits with some minor drawbacks, the best strategy may be to use a combination of protein types to produce optimal results. By varying protein sources, you can get the benefits of each while compensating for the deficits. Professional athletes cycle proteins effectively and blend them for maximum results. So, the next time you are wondering which supplement to use, remember that each of these popular sources has its strengths and its weaknesses. That way, you can best fit them into your nutritional and fitness programs.

 Posted September 19, 2008.

*Definitions:

Resolubilized-dissolved again.

References:

  1. Patell C, Kong SE, McCauley R, Hall JC (2000) Branched-chain amino acids. J Gastroenterol Hepatol >
  2. Boirie Y, Dangin M, Gachon P, Vasson M-P, Maubois J-L. Beaufrere B (1997) Slow and fast dietary proteins differently modulate postprandial protein accretion. Proc Natl Acad Sci USA 94:14930-14935.
  3. Mosoni L, Mirand PP (2003) Type and timing of protein feeding to optimize anabolism. Curr Opin Clin Nutr Metab Care 6(3):301-306.
  4. Dragan I Stroescu V, Stoian I, Georgescu E, Baloescu R (1992) Studies regarding the efficiency of Supro isolated soy protein in Olympic athletes. Rev Roum Physiol 29(3-4):63-70.
  5. Song Y, Igawa S, Horii A (1996) Antioxidant enzymes response to endurance exercise training and dietary proteins in rat skeletal muscle and liver. Appl Human Sci 15(5):219-225.
  6. Mariotti F, Mahe S, Benamouzig R Luengo C, Dare S, Gaudicohon C, Tome D (1999) Nutritional value of [15N]-soy protein isolate assessed from ileal digestibility and postprandial protein utilization in humans. J Nutr 129(11):1992-1997.