I found this:
It is also very interesting to note that whey increases anabolism quickly and to a large extent due to it's fast absorption and high rate of digestion however, these effects are very short lived. It has been shown that whey protein causes amino acid concentrations in the blood to rise rapidly however at the same rate increased oxidation (the use of the amino acids for energy) and so a steady state metabolism was created and no change in overall protein balance took place. Whey is also out of the blood stream very fast, sometimes within fifteen minutes, making it a poor anti catabolic. Some studies have even shown that two hours after taking whey that the blood serum level of amino acids had actually dropped below normal. This debate has recently given rise to much of whey's bad press recently especially to protein sources of casein variety which are absorbed much slower and have great anti-catabolic properties. From this argument it has arisen in some theories that protein sources, especially whey should be combined. It should be noted that whey protein concentrate enters the system a little slower than isolate but is not of as high a quality protein nor is it filtered as much and so can contain higher levels of lactose, fat and possibly cholesterol.
