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What actually happens to the collagen you drink

Swallowed collagen is broken down before it reaches skin, yet 113 trials find gains in elasticity, hydration and joint pain. The signal thought to explain that rests on animal and cell-dish work.

Collagen Peptides

Collagen is sold as though the scoop travels intact to your face. It is broken into amino acids and short peptides first, one of which turns up in blood hours later and is thought to signal your own cells to build collagen. Across 113 trials the gains are real anyway, in skin elasticity, hydration and joint pain, though that signalling step rests on animal and cell-dish work. Amounts spanned 0.4g to 12g a day, with no recommended figure. What is bought is a signal, not a building material.

The findings behind this

1↕
Physical & bodyNothing 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.

★★☆Single study — solid evidence, such as one good trial or a large observational dataset, but not replicated at the top tier.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.Click to keep this openCare for skin and hairCollagen Peptides
2
Physical & bodyMarker fragments peak within 2 hours and last up to a day

Collagen is digested into free amino acids and short peptides. The marker fragments peak in blood 1 to 2 hours after a dose and stay detectable for up to 24.

★★☆Single study — solid evidence, such as one good trial or a large observational dataset, but not replicated at the top tier.These are absorption curves for a few marker fragments, not a clearance time for the ingredient as a whole. Collagen from different animal sources may behave differently. And finding the tough fragment in blood shows it lasts, not that it does anything while it is there.Click to keep this openCare for skin and hairCollagen Peptides
3∿
Physical & bodyShort courses of collagen probably understate what a full one does

The trials ran 4 to 16 weeks at daily amounts spanning 0.4g to 12g, and no recommended figure falls out of them. One 160-person trial used 10g a day.

★★☆Single study — solid evidence, such as one good trial or a large observational dataset, but not replicated at the top tier.The joint trial tested one branded product, and two of its authors work for the manufacturer and for the contract firm that ran it, so an independent repeat is still missing. Several outcomes in the largest synthesis, skin roughness among them, came out flat.Click to keep this openCare for skin and hairCollagen Peptides
4
Physical & bodyNo one has set an upper limit for collagen; the trials stop at 35g

Regulators handle hydrolyzed collagen peptides as an ordinary food protein. The largest dose in the trials, 35g, went to ten men on one occasion, as an absorption test.

★★★Well replicated — this finding’s sources average out to meta-analyses, systematic reviews or high-powered trials.That 35g went to ten men on one occasion, with no long-term follow-up. All ten were men, so nothing here speaks to anyone else. And no formal ceiling means nobody has set one, which is not the same as evidence that any dose is safe indefinitely.Click to keep this openCare for skin and hairCollagen Peptides

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