I have just started drinking casein right before bed about a month ago. It holds me over until morning fairly well. It is hard to tell if I'm making gains from it so far, but I feel better when I wake up.
To address your question Gymratn, yes, casein makes up about 80% and whey is the remaining 20% of milk. They both digest differently. Casein digests slowly, so it is ideal to drink when you will not be able to eat for long periods of time (i.e. before you go to sleep). Casein can help prevent your body from going into a catabolic state. Whey digests very quickly, so it is often taken after workouts. Whey taken after workouts can help increase mass and aid the recovery process. There's more to it, but that's the shorter response. If you use the search function, I'm sure you will get a more informative answer
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