A brand-new analysis just made a striking claim:
"There is no clinical evidence to support the use of collagen supplements to prevent or treat skin aging" [1].
Table of Contents
The Study
Why is this claim about collagen supplements so striking?
It directly contradicts the findings of a previous meta-analysis. That one included 26 randomized controlled trials and was published in 2023. It examined the effects of collagen supplements on skin hydration and elasticity—two key aspects of skin health that decline with age [2].
The statistical analysis showed that collagen peptide supplements significantly improved both metrics:
"The overall pooled effect size of 0.63 (95% CI 0.38, 0.88) indicated that HC supplementation significantly improved skin hydration (z = 4.94, p < 0.00001)...
...HC supplementation significantly improved skin elasticity (z = 4.49, p < 0.00001) compared with the placebo group at a pooled effect size of 0.72 (95% CI 0.40, 1.03)" [2].
And the latest meta-analysis found the same thing when taking all included studies together. Collagen peptide supplements significantly improved skin hydration and elasticity. They also improved wrinkles [1].
But then the authors conducted some subgroup analyses. And that's where they ultimately reached a very different conclusion.
One subgroup they considered was just those studies that weren't funded by pharmaceutical companies. The logic here is that these would be less likely to give a biased result. So how do the numbers look for this subgroup?
There is no longer any statistically significant impact on hydration, elasticity, or wrinkles [1].
A similar thing happened when looking at just high-quality studies. And there were also no statistically significant benefits when considering only studies that were both high quality and not funded by pharmaceutical companies [1].
This looks concerning—because it sounds like what the researchers discovered is this: low-quality studies funded by pharmaceutical companies find benefits for collagen peptide supplements. But high-quality, non-funded studies don't. That raises serious doubts about whether collagen peptides really have the benefits previously reported.
But the story isn't quite so simple.
Digging Deeper
The meta-analysis gives pooled results when taking all studies together. When examining the individual studies that this meta-analysis identified as high quality, a surprisingly different picture emerges.
The meta-analysis uses two common measures of study quality. There are 9 studies total that receive the highest marks on both measures. When the authors looked at just these 9 studies, they concluded there was no benefit overall.
One might expect that none—or at most 1 or 2—of these 9 studies showed benefits. But the data tell a different story: out of these 9, only 1 found no benefit. Another found mixed results. The other 7 all showed positive impacts from collagen supplements.
And when focusing only on the highest-quality studies that aren't funded by pharmaceutical companies?
There are just 5 of these. Of those, four found positive results.
In other words, almost all of the best studies found positive results. So how, then, do the authors wind up with such a deflating conclusion?
It has to do with how the statistics behind a meta-analysis work. They can actually lead to a result that's misleading. There are two reasons why.
1. Standard Mean Differences
There is a challenge when trying to add together the results of several different studies: they don't measure precisely the same things in the same ways.
For instance, one study might describe improvements in skin moisture by measuring how much water is lost through the skin. Another might use electric current to measure moisture content within the skin. Both of these metrics are relevant to improved moisture. But the results cannot be directly combined.
What researchers do is convert specific measures into what's called a standard mean difference (SMD). It's a way to capture the size of an effect on a standard scale. Once that's done, the effect sizes of different studies can be compared and pooled to calculate an overall effect size.
The challenge is that when results are standardized this way—especially when the studies themselves are very different—important context can be lost. The pooled result can end up seeming to contradict the individual findings.
2. Confidence Intervals
The second part of the pooling process that can yield a misleading outcome relates to confidence intervals. These are useful in statistics because they indicate how confident researchers are in the results.
When researchers combine studies where the results are fairly different, the final confidence interval gets larger. It's possible to have a situation where all studies show a positive result, but the size of those results varies a lot. That can produce a conclusion of, in effect, "The study results are so different that there is not enough confidence in what the true effect is."
And here's how this issue shows up in the new study.
For skin hydration, the SMD is 0.33, and the confidence interval is -0.06 to 0.73. That confidence interval means the true impact is estimated to fall somewhere between these numbers. But the fact that it drops below zero is why the result isn't statistically significant—it means it's possible the true impact is no impact [1].
This is technically correct from a statistical point of view. But almost the whole range of possible effect sizes is positive. That means a moderate positive effect is entirely plausible.
It's the same story for elasticity when looking at just the high-quality studies. The confidence interval just barely crosses 0, so the authors declare no significant effect [1].
This approach misses the forest for the trees—especially when the vast majority of high-quality studies, before their measurements were converted into standard mean differences, showed a benefit.
There is an additional reason to think positive effects are likely.
Studies give us a mechanism for how collagen peptides work to affect the skin.
For example, one study investigated how fibroblast cells grown in the lab respond to collagen peptides. Fibroblast cells make collagen and elastin. What researchers saw under the microscope confirmed that skin improvements seen with collagen peptide supplements are driven by positive cellular changes.
The fibroblasts exposed to collagen peptides increased production of collagen, elastin, and another molecule called proteoglycan, which is crucial for skin hydration [3].
A key question remains: when collagen peptides are ingested, do they actually reach the skin?
Numerous human trials show that collagen peptide supplements boost the levels of relevant peptides in the blood. As blood circulates throughout the body, those peptides reach the skin.
A study using both mice and humans confirmed this: the collagen peptides consumed orally do indeed make their way to the skin [4].
But one big limitation of most collagen peptide studies is that they compare collagen peptides to a placebo rather than directly against a protein supplement.
Ideally, protein intake would be matched between groups. That way, any effects on skin can be attributed to collagen peptides specifically—not just to increased protein intake generally.
Currently, there's only one study that directly compares collagen peptides to protein supplements for skin outcomes. The researchers were looking at wound healing rather than skin aging, and they examined burn patients. One group took protein. The other took a matching amount of collagen peptides.
The collagen peptide group experienced a significantly higher wound healing rate compared to the protein group [5].
While that's encouraging, a study on skin aging that directly compares collagen peptides to a matched protein supplement is still needed.
Implications
There are 3 takeaway points from this new meta-analysis.
1. Read the Full Study
It's critical to read the full study and not just rely on the abstract. The abstract of this meta-analysis led many outlets to report that collagen supplements "don't work." The actual data inside the paper tell a more nuanced story—one where the majority of even the highest-quality, independently funded studies found meaningful positive results.
2. Statistical Significance Isn't Everything
More study data may be needed to hit certain thresholds of statistical significance when focused on just the highest-quality trials. But even so, the combined analysis just barely touched the 0 mark. The overall picture may be missing the forest for the trees—especially when almost all the individual studies show positive results, including the highest-quality trials not funded by collagen peptide manufacturers.
New studies continue to emerge. For example, a study published in April looked at the impact of collagen peptides on fibroblasts. Like many others, it found positive impacts on wrinkles, elasticity, and hydration [3].
3. Mechanism of Action
Beyond the many high-quality studies showing that collagen peptides appear to help, laboratory experiments also illuminate the underlying mechanism—providing biological plausibility that reinforces the clinical data. Fibroblast studies show that collagen peptides actively stimulate the production of collagen, elastin, and proteoglycan. Human pharmacokinetic data confirm that orally ingested peptides enter the bloodstream and accumulate in skin tissue. Together, these mechanistic findings provide a coherent explanation for why clinical benefits are observed across so many independent trials—even when the pooled statistical picture falls just short of conventional significance thresholds.
And importantly, there are no known health risks associated with taking collagen peptides.
From the MicroVitamin range
MicroVitamin+ Powder includes collagen peptides as one of its core ingredients, formulated alongside creatine, taurine, and other evidence-based compounds. MicroVitamin+ Powder.
References
1. https://doi.org/10.1016/j.amjmed.2025.04.034
2. https://www.mdpi.com/2072-6643/15/9/2080
3. https://www.mdpi.com/2079-9284/12/2/79
