Foods containing protein- articles

Soy protein & branched-chain amino acids

 As we age, our muscle and whole-body protein metabolism slows down. (Medical Reference 1)  Fortunately, these changes can be offset by exercise, which provides a variety of health benefits for people of any age.  However, our bodies require a good source of energy or fuel for exercise to provide its full benefits.

It has been reported that the branched-chain amino acids (BCAAs), leucine, isoleucine, and valine, are oxidized to provide an important energy source during exercise. (Medical Reference 2)  In addition, the BCAAs, especially leucine, can enhance protein synthesis after exercise and while at rest (Medical References 3-9) and may help prevent muscle breakdown and soreness associated with exercise. (Medical References 10, 11)  In addition to their benefits on protein synthesis and exercise, it has been suggested that BCAA may support better immune function in athletes. (Medical Reference 12)

Soy protein has been shown to be an excellent source of BCAAs. (Medical Reference 13)  The requirements of the BCAAs for human growth and development are 66, 28, and 35 mg/gram of protein for leucine, isoleucine, and valine according to the Food and Agricultural Organization/World Health Organization. (Medical Reference 14)  Isolated soy protein has been reported to contain 82, 49, and 50 mg/gram of protein for these BCAAs, levels well above above human requirements.  Thus, the amino acid pattern of soy protein provides adequate levels of each essential amino acid for normal growth and development. Interestingly, soybeans are the only vegetable to meet these requirements.

In summary, the high quality of soy protein and its BCAAs content make soy an excellent protein food source for good health and exercise. The FDA recommends 25 grams of soy protein per day, as part of a diet low in cholesterol and saturated fat, to reduce risk of heart disease. 

 By Dr. Aaron Tabor, MD
Medical Research Director

Learn more about Soy Benefits-USA
Soy Protein Food-Europe


 1.      Short KR, Vittone JL, Bigelow ML, Proctor DN, Nair KS.  Age and aerobic exercise training effects on whole body and muscle protein metabolism.  Am J Physiol Endocrinol Metab 2004; 286:E92-E101.

 2.      Blomstrand ES, Newsholme EA.  Effect of branched-chain amino acid supplementation on the exercise-induced change in aromatic amino acid concentration in human muscle.  Acta Physiol Scand 1992; 146:293-298.

 3.      Louard RJ, Barrett EJ, Gelfand RA.  Effect of infused branched-chain amino acids on muscle and whole-body amino acid metabolism in man.  Clin Sci (Lond) 1990; 79:457-466.

 4.      Nair KS, Schwartrz RG, Welle S.  Leucine as a regulator of whole body and skeletal muscle protein metabolism in humans.  Am J Physiol Endocrinol Metab 1992; 263:E928-E934.

 5.      Biolo G, Tipton KD, Klein S, Wolfe RR.  An abundant supply of amino acids enhances the metabolic effect of exercise on muscle protein.  Am J Physiol Endocrinol Metab 1997; 273:E122-E129.

 6.      Tipton KD, Ferrando AA, Phillips SM, Doyle D Jr., Wolfe RR.  Postexercise net protein synthesis in human muscle from orally administered amino acids.  Am J Physiol Endocrinol Metab 1999; 276:E628-E634.

 7.      Rasmussen BB, Tipton KD, Miller SL, Wolf SE, Wolfe RR.  An oral essential amino acid-carbohydrate supplement enhances muscle protein anabolism after resistance exercise.  J Appl Physiol 2000; 88:386-392.

 8.      Blomstrand E, Saltin B.  BCAA intake affects protein metabolism in muscle after but not during exercise in humans.  Am J Physiol Endocrinol Metab 2001; 281:E365-E374.

 9.     Layman DK.  Role of leucine in protein metabolism during exercise and recovery.  Can J Appl Physiol 2002; 27:646-663.

 10.  MacLean DA, Graham TE, Saltin B.  Branched-chain amino acids augment ammonia metabolism while attenuating protein breakdown during exercise.  Am J Physiol 1994; 267:E1010-E1022.

 11.  Nosaka K.  Muscle soreness and amino acids.  Training J 2003: 289:24-28.

 12.  Bassitt RA, Sawada LA, Bacurau RF, Navarro F, Martins E Jr., Santos RV, Caperuto EC, Rogeri P, Costa Rosa LF.  Branched-chain amino acid supplementation and the immune response of long-distance athletes.  Nutrition 2002; 18:376-379.

 13.  Kolar CW, Richert SH, Decker CD, Steinke FH, van der Zanden RJ.  “Isolated Soy Protein”, Chapter VIII in “New Protein Foods”, Vol. 5, Seed Storage Proteins, ed. Altschul AA, Wilcke HL, Orlando: Academic Press, 1985.

14.  Food and Agricultural Organization/World Health Organization/United Nations University.  Energy and Protein Requirements.  Report of a joint FAO/WHO/UNU expert consultation.  Technical Report Series No. 724.  Geneva: World Health Organization, 1985. 

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