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How Protein Supplements for Athletes Work: New Research


Athletes who are looking for help with muscle growth and strength often turn to the bottle—one containing high-protein supplements or beverages, that is. Two new studies explain how the amino acids in these products affect protein production and how the timing of using these supplements can provide the best results.

Timing of your protein supplement affects benefit

High-protein supplements in the form of powders, beverages, and nutrition bars are popular among athletes, especially weightlifters and other serious athletes. These supplements typically contain whey proteins, although soy, casein, milk, and egg proteins are also common ingredients.

Amino acids are the building blocks of proteins, and the amino acid leucine is one that was the focus of investigation in one of two recent studies that evaluated the effect of protein synthesis in recreational athletes. Leucine partners with the amino acids isoleucine and valine to repair muscles, produce energy, burn visceral fat, and regulate blood sugar levels.

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One study, conducted at McMaster University, compared the impact of taking a single large dose of whey protein (25 g) immediately after exercise versus taking 10 smaller doses (2.5 g) over a period of time. Eight men (mean age, 22 years) participated in both treatment arms of the study, and the exercise they performed was 8 sets of 8 repetitions on a leg-extension machine. Researchers found that when men took the 25 grams of whey protein immediately after they exercised, they had a greater increase in muscle protein synthesis than they did when they took the smaller doses.

In the second study, eight active duty military personnel (7 men, 1 woman; mean age, 24 years) consumed a high-protein beverage that contained 10 grams of protein while exercising on a stationary bicycle. During one exercise session, the beverage included 3.5 grams of leucine; during a second session, the beverage contained only 1.87 grams of leucine. Muscle protein synthesis was one-third greater after the volunteers consumed the beverage with the higher leucine content than after taking the lower one.

The results of these two studies indicate two important findings for athletes. One, when it comes to taking high-protein supplements, timing matters: immediately after exercise seems to be best. Two, leucine plays an essential part in stimulating muscle growth after exercise. While high-protein supplements are popular among athletes, they are also helpful for people who have cancer or AIDS, and can be used to help with weight loss as well.

Pasiakos SM et al. American Journal of Clinical Nutrition 2011; 94(3): 809-18
West DWD et al. American Journal of Clinical Nutrition 2011; 94(3): 795-803

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