Even though both protein shakes had the same amount of protein, the whey one made the key muscle-building amino acid (leucine) in the blood much higher than the collagen one.

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.

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.

Collagen peptide consumption results in improved nitrogen balance relative to whey protein in elderly populations.

If you lift weights and drink a protein shake after your workout, one made only with fast-digesting whey might give your body a quicker boost of key muscle-building amino acids than a mix with mostly slow-digesting casein.

When rats ate a larger dose of regular whey protein, their blood had more leucine than when they ate the same amount of hydrolyzed whey protein an hour later.