Whey is a rapidly digesting protein found in milk. Casein is a slowly digesting protein that also comes from milk. Which one or combination is better for muscle building after weight training? A study published in the International Journal of Sport Nutrition and Exercise Metabolism put 3 options to the test with experienced weight lifters enrolled in a 9-week resistance training program.
After each workout, subjects got a protein shake made with all whey protein, half whey and half casein or 20% whey and 80% casein. Body composition and strength measurements taken before and after the 9-week program showed similar increases across all groups. The only difference was in blood tests that showed higher leucine bioavailability after consuming the all when and 50% whey shakes. Leucine is one of the three Branched Chain Amino Acids (BCAAs).