Roles of Protein and How to Choose

Protein is made up of individual chains of amino acids that do a lot of important work on our body¹¹. One of the functions is to support the growth and repair of muscle and tissue in our body^1,11. However, the time taken to break down protein into amino acids and deliver them to muscles varies and depends on the types of protein⁴. Both fast and slow-release proteins are very useful in reaching fitness and body goals, ².

Fast-Release Protein

Fast-release proteins breakdowns quickly which result in a spike of amino acids to the muscles¹⁰. As they are easy to digest, these proteins are ideal when someone needs the protein to ease muscles soreness or post-workout⁴. According to a study, this fast-release protein such as the whey protein is beneficial for skeletal muscle adaptations, which will result in greater gains in lean mass and strength compared to slow-release protein^4,6.

Whey protein is one of the most popular fast release proteins. It is more soluble in the acidic environment in the stomach which leads to more rapid digestion⁹. Therefore, whey protein supplementation after post-exercise can be an effective strategy to improve the protein synthesis recovery after resistance exercise, enhancing muscular growth and strength^3,7.

Slow-Release Protein

Slow-release protein such as casein results in an extended supply of amino acids over a longer period¹². As casein releases and digests amino acids slowly, it is often consumed before a sweat session or before bed to improve muscle recovery and reduce muscle breakdown during sleep^4,12. This makes casein an ideal night-time recovery protein⁸. In addition, due to its slower acting, it can help to keep the stomach full for a longer period of time and balance the blood sugar levels which are ideal for people with type 2 diabetes to stay full and avoid spikes in blood sugar levels^5,9.

In a nutshell,

By taking either fast or slow or even both releasing protein, what matters is for us to understand how they work and how they can be a useful tool for our diet so that it aligns with our body goals and needs.

References

¹Agostini, D., Donati Zeppa, S., Lucertini, F., Annibalini, G., Gervasi, M., Ferri Marini, C., Piccoli, G., Stocchi, V., Barbieri, E., & Sestili, P. (2018). Muscle and bone health in postmenopausal women: role of protein and vitamin d supplementation combined with exercise training. Nutrients, 10, (1103). https://doi.org/10.3390/nu10081103

²Deutz, N. E. P., Bauer, J. M., Barazzoni, R., Biolo, G., Boirie, Y., Bosy-Westphal, A., & Calder, P. C. (2014). Protein intake and exercise for optimal muscle function with aging: Recommendations from the ESPEN Expert Group. Clinical Nutrition, 33(6), 929-936. https://doi.org/10.1016/j.clnu.2014.04.007

³Fabre, M., Hausswirth, C., Tiollier, E., Molle, O., Louis, J., Durguerian, A., & Bigard, X. (2017). Effects of post-exercise protein intake on muscle mass and strength during resistance training: is there an optimal ratio between fast and slow proteins? International Journal of Sport Nutrition and Exercise Metabolism, 27(5), 448–457. https://doi.org/10.1123/ijsnem.2016-0333

⁴Jäger, R., Kerksick, C. M., Campbell, B. I., Cribb, P. J., Wells, S. D., Skwiat, T. M., & Antonio, J. (2017). International Society of Sports Nutrition Position Stand: protein and exercise. Journal of the International Society of Sports Nutrition, 14(1). https://doi.org/10.1186/s12970-017-0177-8

⁵Jan, S. A., Habib, N., Shinwari, Z. K., Ali, M. & Ali, N. (2021). The anti-diabetic activities of natural sweetener plant Stevia: An updated review. SN Applied. Science. 3, (517). https://doi.org/10.1007/s42452-021-04519-2

⁶Knuiman, P., Hopman, M.T.E. & Mensink, M. (2015). Glycogen availability and skeletal muscle adaptations with endurance and resistance exercise. Nutrition & Metabolism, 12, 59 . https://doi.org/10.1186/s12986-015-0055-9

⁷Lima, Y. C., Kurauti, M. A., da Fonseca Alves, G., Ferezini, J., Piovan, S., Malta, A., & Mareze-Costa, C. E. (2019). Whey protein sweetened with Stevia rebaudiana Bertoni (Bert.) increases mitochondrial biogenesis markers in the skeletal muscle of resistance-trained rats. Nutrition & Metabolism, 16(1). https://doi.org/10.1186/s12986-019-0391-2

⁸Madzima, T. A., Melanson, J. T., Black, J. R., & Nepocatych, S. (2018). Pre-Sleep Consumption of Casein and Whey Protein: Effects on Morning Metabolism and Resistance Exercise Performance in Active Women. Nutrients, 10(9), 1273. https://doi.org/10.3390/nu10091273

⁹Mignone, L. E., Wu, T., Horowitz, M., & Rayner, C. K. (2015). Whey protein: The “whey” forward for treatment of type 2 diabetes?. World Journal of Diabetes, 6(14), 1274–1284. https://doi.org/10.4239/wjd.v6.i14.1274

¹⁰Mulet-Cabero, A.-I., Torcello-Gómez, A., Saha, S., Mackie, A. R., Wilde, P. J., & Brodkorb, A. (2020). Impact of caseins and whey proteins ratio and lipid content on in vitro digestion and ex vivo absorption. Food Chemistry, 126514. https://doi.org/10.1016/j.foodchem.2020.12651

¹¹Nie, A., Sun, B., Fu, Z. & Yu. D. (2019). Roles of aminoacyl-tRNA synthetases in immune regulation and immune diseases. Cell Death and Disease, 10, 901. https://doi.org/10.1038/s41419-019-2145-5

¹²Trommelen, J., Weijzen, M. E. G., van Kranenburg, J., Ganzevles, R. A., Beelen, M., Verdijk, L. B., & van Loon, L. J. C. (2020). Casein Protein Processing Strongly Modulates Post-Prandial Plasma Amino Acid Responses In Vivo in Humans. Nutrients, 12(8), 2299. https://doi.org/10.3390/nu12082299