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Open WellbeingWhat the studies actually measured

Skin, hair and nails

Collagen peptidesand Skin moisture content

Only one source here so far, and it measured higher skin moisture content.

How sure anyone can be

Moderate certainty, level 3 of 4

Further research may change this.

The numbers reported

One source’s range, drawn against its own line of no difference and scaled to its own numbers.

0.771.25 standardised effect size1.74

This range stays on one side of the no-difference line.

Bar the confidence interval — the range the true effect is likely to sit inNotch the number the source reportedLine where there would be no difference at all

One source, newest first

What we read is the published abstract, not the full paper, so a blank below may still be printed in the paper itself. A fixed rule worked this out from the source’s own fields. Nobody checked this rating by hand.

  • Systematic review, 2025

    Moderate certainty, level 3 of 4

    Effects of collagen-based supplements on skin's hydration and elasticity: A systematic review and meta-analysis.

    Indian J Dermatol Venereol Leprol. 2025;91(6):730-740. doi:10.25259/IJDVL_1165_2023. PMID:40826844.

    Number reported
    1.25 standardised effect size
    Which way it went
    Higher
    Likely range
    0.77 to 1.74
    Source’s own words
    standardized mean difference in skin hydration vs placebo
    Who was studied
    Adult
    Compared with
    placebo
    Amount taken
    1 to 10 g/d
    For how long
    Not in the abstract
    Disagreement between studies
    Moderate heterogeneity (I2 = 55.5-56.5%)
    Kind of record
    Journal article
    How this rating was reachedstarts at High, one step down: imprecision
    1. Starts at High
    2. Imprecision brought it down to Moderatethe abstract does not state how many participants were pooledNot in the abstract
    3. Ends at ModerateOne step down.
    Checked, nothing to step it down for
    risk of bias and indirectness
    Inconsistency
    No disagreement reported, and no count of studies behind it

    Imprecision stops at the first check that applies; others may apply too.

    AI-reviewed & signed — an AI agent re-read this finding against the saved source and checked that the quote, the numbers, the units and the direction match it. No person read it. The owner authorised the agent to sign the batch with the owner's key, and every build rechecks that signature against these exact bytes.

    Read the abstract on PubMed

What is still missing from these readings

  • One do not say how many people took part.
  • For how long — Not in the abstract.

Something nobody wrote down is never a zero and never a guess.

Still to read for Collagen peptides

Two of the seven things on our list for Collagen peptides have no reading here yet:

  • Heart Rate (Continuous)
  • Interleukin-6

Still to read means nobody here has got to it, not that it was tried and did nothing or that no research exists. A pairing on no list is not a gap: we never set out to read it.

Read next

This is a library, not advice. No recommendation, no dose, no diagnosis, no ranking. We never ask about your symptoms, and nothing here is tailored to you.