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Randomized trial · measured the question itself

A 12-week collagen trial in 99 Japanese women: more moisture, no elasticity change

Miyanaga and colleagues · Skin pharmacology and physiology · 2021

Original title: Oral Supplementation of Collagen Peptides Improves Skin Hydration by Increasing the Natural Moisturizing Factor Content in the Stratum Corneum: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial.

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What the study found

Mixed

Collagen raised skin water content and cut water loss. Skin elasticity and skin thickness did not change.

The study at a glance

Type of study
Randomized trial
Who or what was studied
99 people · 99 healthy Japanese women aged 35 to 50
What was tested
1 g or 5 g of collagen peptides a day for 12 weeks, vs placebo
What it measured
The question itself: skin wrinkles, elasticity and hydration
Daily amount
5 g a day
How long
12 weeks
Who has a stake
No disclosure in PubMed
No disclosure in PubMed.
Journal
Skin pharmacology and physiology, 2021
Source
PubMed record 33774639. This page is based on the abstract only.

How much this study counts

  • ✓Randomized: people were put into groups by chance, so the groups start out alike.
  • ✓Compared with a placebo, a dummy treatment.
  • •Medium size: 99 people.
  • •Lasted 12 weeks.
  • ✓Measured the question itself: skin wrinkles, elasticity and hydration.
  • •The PubMed record has no conflict-of-interest statement.
  • •Summarized from the PubMed abstract only. The full paper may hold details the abstract leaves out.

✓ Strength– Limit• Note

These points come from fixed rules about the type of study, its size and length, what it measured, and who has a stake. Every study on Digestery gets the same rules.

Where this study sits

Each dot is one on-topic paper on this question. Steps near the top answer the question more directly.

↑ Stronger evidence

  1. Trials in people: wrinkles, skin elasticity and moisture

    15

    13 benefit, 2 mixed

    ↑ This study is the ringed dot

  2. Trials in people: other measures

    1

    1 benefit

  3. Trials in people: lab tests or safety

    0

    None among the papers we read.

  4. Population studies

    0

    None among the papers we read.

  5. Blood levels and genes

    0

    None among the papers we read.

↓ Weaker evidence

  • Points to benefit
  • Mixed
  • No difference
  • No direction
  • Points to harm

How it fits with the other research

The short answer to “Does collagen reduce skin aging?”

Unclear; higher-quality trials found no effect.

Confidence: low. Based on 22 on-topic papers.

Read the full answer

Of the other 14 papers on the same step: 13 benefit, 1 mixed. This one found mixed. It differs from most of them.

  • Quoted in “What we found”: Not every trial agreed. In 99 women, collagen raised skin water content but not elasticity. A trial lasting 16 weeks saw no change in elasticity or hydration.
  • Part of the finding “Some trials found no change in key measures”.
  • Open item for a person: Miyanaga 2021 and Kim 2022 name trial registrations in the abstract that are missing from trialreg; Miyanaga 2021 was registered retrospectively.

Other papers on the same step

See all 22 studies on this question

How this page was made

Label

First read of the abstract
Claude Sonnet
Independent second read
Claude Haiku
Differences settled
The two reads differed. The reviewer checked the abstract and kept the first read. Claude Opus 5.5.
Headline
Claude Sonnet, from the checked study record. A script checked its numbers and wording.
Numbers
Checked against the abstract by a script
“How much this study counts”
Fixed rules, the same for every study
Source check by a person
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