Researchers in Finland discovered a unique benefit of whey protein. In a recent study, they fed a group of older men 15 grams of whey protein isolate before and after a session of resistance exercise. Muscle biopsies from the thigh were collected before, one hour after and 48 hours after exercise to determine expression of the androgen (testosterone) receptor. Androgen receptors are what testosterone binds to in order to elicit their anabolic (muscle building) effects in target tissues.
Androgen receptor mRNA responses were variable but tended to increase more during the whey protein isolate trial. The average increase one hour post-exercise was about 25% and this was maintained at 48 hours post-exercise. In contrast, there was little change in average androgen receptor expression during the placebo trial.
The authors speculated that the greater expression of androgen receptors in skeletal muscle may allow for greater uptake of testosterone from the blood. This represents one way in which whey protein augments anabolism in response to resistance training.