Nothing you swallow reaches your skin as collagen; the gains are real
It is broken into amino acids and short peptides before absorption. Across 113 trials the gains in skin elasticity, hydration and joint pain are real anyway.
What the study found
Collagen is digested to fragments before it ever reaches skin
Nothing you swallow arrives at your face as collagen. It is broken into amino acids and short peptides, one turning up intact in blood hours later and thought to signal your own cells to build collagen. Across 113 trials the gains are real anyway: skin elasticity, hydration, joint pain.
The caveat · Signalling rests on animal studies
Finding the fragment in blood shows it survives digestion; it does not show it did anything afterwards. The signalling step rests on animal and cell-dish work rather than on the human trials the reviews cover. That headline pools 113 trials through 16 earlier reviews, so its precision is theirs rather than its own, and several outcomes within it, including skin roughness and two joint sub-scores, came out flat. The peptide work came from a research institute owned by a collagen manufacturer.