Sports nutrition products are used by individuals of all athletic levels to improve performance in sports and help maintain overall health. Sports nutrition has expanded from athlete-focused nutrition to include a wide variety of product categories, such as nutritional supplements, beverages and bars. Soy protein is a critical ingredient in sports nutrition products because it is a widely available, complete, high-quality protein.
Protein helps muscles grow and recover during exercise. Muscle gain occurs when growth, or skeletal muscle protein synthesis (SMPS), exceeds loss, or skeletal muscle protein breakdown (SMPB)
1. When combined with proper nutrition, resistance exercise, such as weight lifting, can lead to muscle gain over time
1. Amino acids, the building blocks of protein, stimulate muscle synthesis in the period following a workout, driving additional muscle gain
2,
3,
4,
5. Two specific amino acids, glutamine and arginine, help regulate muscle protein balance
6,
7. Soy protein contains more glutamine and arginine than whey protein or casein. Arginine, as well as the branched chain amino acids leucine, valine and isoleucine, may help with muscle recovery. The branched chain amino acids are utilized during endurance exercise to provide energy to working muscles
8,
9,
10.
Soy protein isolate, whey protein and casein are three proteins widely used in sports nutrition. Their differing digestion rates and amino acid ratios give them unique functionality for inclusion in sports nutrition products
11,
12,
13,
14. Consuming a combination of proteins with different digestion rates may enhance lean body mass gains by promoting longer periods of muscle growth after exercise
15,
16. Any combination of soy protein isolate, casein and whey protein will be a nutritionally “complete protein,” because each has a PDCAAS (Protein Digestibility Corrected Amino Acid Score) of 1.00. The optimal formulation for a blend of soy protein isolate, casein and whey protein both jump-starts muscle development and maintains nutrient delivery to muscles during and post-exercise.
Athletes of all levels should read packages and labels carefully to determine which type(s) of protein each sport nutrition product includes and strive for a combination of soy protein isolate, whey protein and casein. It is important to consider protein and calories from sports nutrition products as part of total dietary intake to maintain a healthy body weight. Lastly, many myths exist about the impact of increased soy protein intake and may stop athletes from including soy protein in their diet. Knowing the truth about soy protein is important for making the right sports nutrition choices.
View all sources cited
1Phillips SM: Protein requirements and supplementation in strength sports. Nutr 20:689-695, 2004.
2Biolo 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 273(1 Pt 1):E122-129, 1997.
3Dreyer HC, Drummond MJ, Pennings B, Fujita S, Glynn EL, Chinkes DL, Dhanani S, Volpi E, Rasmussen BB: Leucine-enriched essential amino acid and carbohydrate ingestion following resistance exercise enhances mTOR signaling and protein synthesis in human muscle. Am J Physiol Endocrinol Metab 294(2):E392-400, 2008.
4Tipton KD, Elliott TA, Cree MG, Wolf SE, Sanford AP, Wolfe RR: Ingestion of casein and whey proteins result in muscle anabolism after resistance exercise. Med Sci Sports Exerc 36(12):2073-2081, 2004.
5Børsheim E, Tipton KD, Wolf SE, Wolfe RR: Essential amino acids and muscle protein recovery from resistance exercise. Am J Physiol Endocrinol Metab 283(4):E648-57, 2002.
6Jepson MM, Bates PC, Broadbent P, Pell JM, Millward DJ: Relationship between glutamine concentration and protein synthesis in rat skeletal muscle. Am J Physiol 255:E166-172, 1988.
7DiPasquale M, Mauro G: “Amino Acids and Proteins for the Athlete — The Anabolic Edge.” Boca Raton: CRC, 1997.
8Paddon-Jones D, Børsheim E, Wolfe RR: Potential ergogenic effects of arginine and creatine supplementation. J Nutr 134(10 Suppl):2888S-2894S, 2004.
9Kasperek GJ, Snider RD: Effect of exercise intensity and starvation on activation of branched-chain keto acid dehydrogenase by exercise. Am J Physiol. 252(1 Pt 1):E33-37, 1987.
10Wagenmakers AJ: Muscle amino acid metabolism at rest and during exercise: role in human physiology and metabolism. Exerc Sport Sci Rev: 26:287-314, 1998.
11Boirie Y, Dangin M, Gachon P, Vasson MP, Maubois JL, Beaufrère B: Slow and fast dietary proteins differently modulate postprandial protein accretion. Proc Natl Acad Sci USA 94(26):14930-14935, 1997.
12Farnfield MM, Trenerry C, Carey KA, Cameron-Smith D: Plasma amino acid response after ingestion of different whey protein fractions. Int J Food Sci Nutr 8:1-11, 2008.
13Bos C, Metges CC, Gaudichon C, Petzke KJ, Pueyo ME, Morens C, Everwand J, Benamouzig R, Tomé D: Postprandial kinetics of dietary amino acids are the main determinant of their metabolism after soy or milk protein ingestion in humans. J Nutr 133(5):1308-1315, 2003.
14.Lacroix M, Bos C, Léonil J, Airinei G, Luengo C, Daré S, Benamouzig R, Fouillet H, Fauquant J, Tomé D, Gaudichon C: Compared with casein or total milk protein, digestion of milk soluble proteins is too rapid to sustain the anabolic postprandial amino acid requirement. Am J Clin Nutr 84(5):1070-1079, 2006.
15Hartman JW, Tang JE, Wilkinson SB, Tarnopolsky MA, Lawrence RL, Fullerton AV, Phillips SM. Consumption of fat-free fluid milk after resistance exercise promotes greater lean mass accretion than does consumption of soy or carbohydrate in young, novice, male weightlifters. Am J Clin Nutr 86(2):373-381, 2007.
16Kerksick CM, Rasmussen CJ, Lancaster SL, Magu B, Smith P, Melton C, Greenwood M, Almada AL, Earnest CP, Kreider RB. The effects of protein and amino acid supplementation on performance and training adaptations during ten weeks of resistance training. J Strength Cond Res 20(3):643-653, 2006.