Help build lean muscle with Optimum Nutrition Gold Standard 100% Casein. This faster digesting protein is desirable immediately before and after exercise to help you refuel your recovering muscles. Protein that can be slowly digested and absorbed may be more beneficial at other times including bedtime. Casein products are acid sensitive and will thicken in the stomach. Compared to some other proteins, it can take longer for our Gold Standard 100% Casein to be broken down into its amino acid subcomponents. By using only premium micellar casein as a protein source, we've created a formula that sets the standard for slow digesting protein support. Optimum Nutrition is part of the Glanbia global nutrition group and has been setting the Gold Standard in sports nutrition for more than 30 years — helping performance-focused athletes achieve their goals. We are proud to say that we are one of the few sports nutrition companies who own and operate our own production facilities. We take as much pride and care in crafting our award-winning supplements as our consumers do with crafting their fitness accomplishments.