Casein is well known as a “time-release” protein because of its slow absorption rate in the gut.
This means that it feeds your cells with amino acids at a low level over a long period of time.
For this reason, it’s called “anti-catabolic” and helps reduce muscle breakdown (7).
One study tested digestion speed by providing participants with either a casein or whey protein shake. Researchers monitored the blood amino acid content, specifically the key amino acid leucine, for seven hours after ingestion (8).