The study first tested 40 grams of casein against a non-protein placebo and found MPS rates were approximately 22% higher in the group who consume 40 grams of protein during overnight.
The study also compares 30 g of protein to 40 g to see if there would be any differences in MPS rates and they found that 40 g was better than 30.
Having a slow digesting protein like casein can be beneficial to increasing your progress in the gym. If you can’t stand the taste of casein protein, then eating something like eggs, that has a full amino acid profile and slow digesting, can be use instead. Whey may not be as good because whey protein digests to quickly so you’re not getting a prolonged rise in plasma amino acid as you would by consuming casein.