To be effective, protein must be broken down into a smaller particle size within approximately 90 minutes of consumption. This transit time represents the time from which the whey powder passes from the stomach through the small intestine where digestion/absorption primarily occurs; from there it will be assembled into muscle protein (a bio-usable form). To visualize this process, think of a large table being moved into a room through a door that is too small. The table must first be broken down to pass through the doorway before it can be reassembled and used. Undigested whey protein will simply be excreted from the body, resulting in wasted amino acids.

Furthermore, when whey protein is not broken down into the smallest composition, it creates large peptides that can cause discomfort such as bloating, nausea and cramping. These symptoms should not be confused with lactose intolerance. Lactose is not present in whey isolates; therefore, the underlining cause of the discomfort is peptide sensitivity.