For older guys around 74, drinking a shake with 20 grams of whey protein helps their muscles build new protein better after a meal than the same amount of casein or broken-down casein.

After drinking whey protein shakes every day for a week, older women’s muscles kept building up new protein even on days they didn’t exercise—collagen protein didn’t do this at all.

When older women drink whey protein shakes, their muscles start repairing and growing faster—especially if they also do leg exercises—while collagen protein shakes don’t do much unless they exercise, and even then, it’s much weaker.

One scoop of whey protein has over five times more of the key muscle-building amino acid (leucine) than one scoop of collagen protein—even though both have the same total protein.

If a young guy drinks a shake with 25 grams of whey protein, his body absorbs more essential amino acids over 6 hours compared to drinking the same amount of casein protein.

When older guys drink a whey or pre-digested casein protein shake, the protein shows up in their blood faster than when they drink regular casein — meaning it gets absorbed more quickly.