DAIRY PROTEINS & RECOVERY FROM RESISTANCE EXERCISE

Milk’s protein explains in large part its beneficial effects on muscle mass and body composition described above. Milk protein has been shown to result in a greater stimulation of whole body protein synthesis and a higher whole-body retention of dietary nitrogen than soy protein (43,48). Also, milk proteins appear to be superior to, or at least equivalent to, either isolated whey or casein alone in supporting postprandial dietary nitrogen utilization (49). One study demonstrated that casein resulted in higher protein synthesis and lower oxidation of amino acids, as evidenced by lower urea production, than consumption of a soy protein meal (50).

Studies of individual milk proteins, casein and particularly whey, support an increase in skeletal muscle amino acid uptake, protein synthesis, or muscle mass under conditions of resistance exercise (6,16,18-23,51,52). A comparison of whey versus casein (20 g each) consumption one hour after resistance exercise found that both dairy proteins stimulated an equivalent net amino acid uptake (i.e., positive net muscle protein balance) compared to a placebo (18).

Considerable attention has focused on the benefits of whey protein either in various formulations or alone for persons participating in resistance exercise. A recent investigation demonstrated greater increases in lean body mass and muscle strength following 10 weeks of resistance training and intake of 20 g protein (14 g whey and casein protein, 6 g free amino acids) consumed one hour before and after exercise compared to a carbohydrate placebo (52).

Moderately increasing protein intake above the RDA by consuming high-quality protein foods such as milk, while regularly participating in resistance exercise, may help older adults retain muscle mass and reduce the risk of sarcopenia.

Another investigation found that consuming a beverage providing a small amount of whey protein (10 g) with carbohydrate (21 g) following resistance exercise resulted in a greater increase in muscle protein synthesis compared to a carbohydrate only beverage in eight healthy resistance-trained (weight lifting) young men (51). In a 12-week, double-blind study of 13 male recreational body builders, whey protein isolate was shown to improve body composition (i.e., increase lean body mass and decrease body fat) and strength that accompany routine resistance exercise to a greater extent than was achieved with equivalent casein consumption (20). Additional support for the benefits of whey protein (with or without creatine) on body composition, muscle fiber size, and muscle strength was provided by findings from a subsequent study in 26 resistance-trained men (22).

Studies report that whey protein is most effective in augmenting the effects of resistance exercise when consumed within an hour or so before or after resistance exercise (6,19,21).

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