I was wondering what everyone's take on this is: is it more beneficial to use--in general--a straight whey protein, or a whey + casein mixed protein?
The reason I pose this question is that opinions on this subject seem to be somewhat contradictory. I remember when it was widely advocated that one should use a mixed protein so as to get the increase in MPS (muscle protein synthesis)rates from the rapid rise in amino acid levels from the whey portion, while maintaining a steady supply of aminos to take advantage of this increased MPS rate through the casein portion.
Then it seems that some began to advocate the use of straight whey and/or whey and casein hydrolysates. The idea being that the more rapid the rise in amino acid levels, certain ones in particular, the greater the increase in MPS rates, and that, in parrticular, the greater the difference between "resting" (or baseline) Leucine levels and the spiked level, the greater the increase in MPS rates.
So, allowing amino acid levels in the blood to drop and then spike very rapidly and very high would create the greatest increase in MPS rates. Whey and/or whey and casein hydrolysates would thus seem to be the logical choice.
However, I still see people advocating the use of mixed proteins. Their reasoning is that research that has now been replicated a half-dozen times or so seems to indicate that because whey is so rapidly absorbed and causes such a large increase in amino acid levels, the body attemps to counter this and maintain homeostasis by filtering out much of these amino acids through the liver. Thus, there are not enough amino acids left in the blood beyond a very transient spike for the muscles to be able to take advantage of the temporary increase in MPS rates.
I would love it if the powers to be here could bring this question to the attention of Dr. Lowery, or one of the many other very knowledgeable people here.