Supplements, Honestly: Collagen, Biotin, and What the Research Says
Collagen and biotin are marketed harder to women in midlife than almost anything else. Here is what the research actually shows, including who funded which studies.
Hair, skin and nail supplements are among the most aggressively marketed products aimed at women in midlife, and the marketing is effective because the underlying concern is real. Collagen genuinely does decline. Hair genuinely does thin. The question is whether the products sold in response do anything about it.
This guide covers what the evidence shows on collagen and biotin, why the funding behind a study turned out to matter more than usual, and where supplements are actually worth taking. It is meant to sharpen your conversation with a clinician, not replace it.
Collagen: what the largest recent analysis found
In 2025, the American Journal of Medicine published a meta analysis by Myung and Park pooling 23 randomized controlled trials covering 1,474 participants. Its conclusion was direct: there is currently no clinical evidence to support the use of collagen supplements to prevent or treat skin aging.
That is a stronger statement than the usual academic hedge, and it is worth understanding how the authors got there, because the path is the interesting part.
Why the funding source turned out to matter
The pooled analysis initially did show improvements. Hydration, elasticity and wrinkles all appeared to benefit when every trial was combined.
Then the authors separated the trials by funding. Studies without industry funding showed no benefit. Studies backed commercially reported positive effects. When the analysis was restricted to higher quality studies only, no significant effect appeared in any outcome. The elasticity benefit, the most commonly cited claim in collagen marketing, was concentrated in the low quality studies.
This is the finding that matters for anyone deciding whether to spend money here, and it is almost never included in product copy.
What the supplement industry says back
Bloomly's position is that you should see the disagreement rather than only our side of it.
Industry bodies including BioCell Technology, the Collagen Stewardship Alliance and GROW publicly disputed the analysis. Their arguments: that it lumped meaningfully different collagen formulations together as though they were interchangeable, that it misclassified some funding sources, and that it disregarded other meta analyses that reached more favorable conclusions.
Those are not unreasonable objections in principle. Formulation differences are real in supplement research generally. Whether they explain away a funding split this clean is a different question, and one the industry response does not fully answer. Our read is that the burden sits with the products to demonstrate benefit in independently funded, higher quality trials, and that has not happened yet.
There is also a safety point that gets little attention. AAD notes that most collagen supplements lack third party verification, and that marine sourced collagen carries uncertainty about heavy metal content including mercury, because you cannot confirm what is not tested for.
Biotin: useful for a deficiency, and it can distort your lab results
Biotin, sometimes labeled vitamin H or B7, is the other headline ingredient in hair and nail supplements. The evidence picture here is narrower than the marketing but not empty.
The core issue is that biotin deficiency is rare. AAD's guidance is that biotin supplements should be taken only if you actually have a deficiency, which most people do not. Supplementing beyond a deficiency has not been shown to grow hair in people who were not deficient to begin with.
The part that is genuinely worth knowing, and that many women taking these products have never been told, is that high dose biotin can interfere with laboratory testing, thyroid tests in particular. That has practical consequences. If you are taking a hair and nail supplement and your thyroid results come back unexpected, the supplement is a plausible explanation, and it is worth telling whoever ordered the test that you are taking it. Given how often thyroid function is checked as part of a hair loss workup, this specific interaction lands right in the middle of the situation these products are bought for.
Where supplements are actually worth taking
None of this means supplements are pointless. It means the useful case is a specific one: correcting a deficiency that has been identified.
Iron is the clearest example. Iron deficiency is a real and correctable cause of hair shedding, and it is one of the standard blood tests in a hair loss workup for exactly that reason. Harvard Health's guidance on female pattern hair loss is that iron supplementation is appropriate when a deficiency has been identified, not as a default. Thyroid dysfunction follows the same logic: worth testing, worth treating if present, and not addressed by an over the counter supplement.
The distinction is between replacing something you are measurably short of, which works, and supplementing something you have enough of in the hope of a cosmetic effect, which is where the evidence runs out.
AAD's summary is the practical one: most people get the vitamins and nutrients they need from a well balanced diet, and it is worth talking to a dermatologist before starting a supplement rather than after.
What this does not mean
A few clarifications, because this topic invites overcorrection.
It does not mean your hair or skin concern is imaginary. The changes are real, and this article is about one category of response to them, not about whether the problem exists.
It does not mean nothing works. Sunscreen and retinoids have real evidence for skin, and topical minoxidil has real evidence for pattern hair loss. We cover those in What Actually Works for Aging Skin and Which Kind of Hair Loss Is It?.
And it does not mean collagen is harmful. The finding is an absence of demonstrated benefit, which is a different claim, alongside a verification gap worth knowing about.
Want a quick starting point?
If you are trying to sort out which of these questions applies to you, our Find Your Care quiz can point you toward the right next step in a couple of minutes.
Frequently asked questions
Should I stop taking collagen if I think it is helping?
That is a reasonable conversation to have with a clinician rather than a decision this article should make for you. What the evidence supports is that you should not expect a measurable skin benefit, and should weigh the cost accordingly. If you continue, third party verified products address at least the contamination question.
Is biotin dangerous?
Not in the sense of toxicity. The practical risk is the lab interference, particularly with thyroid testing. Tell whoever orders your blood work that you are taking it.
What about hair, skin and nail multivitamins generally?
The same logic applies to each ingredient individually. Where a deficiency exists and has been identified, replacement helps. Where it does not, the evidence for a cosmetic effect is weak. Combination products also make it harder to know what you are actually taking and at what dose.
Does any of this change if I am on a GLP-1 medication?
Rapid weight loss can produce genuine nutrient shortfalls, so deficiency becomes more plausible rather than less. That makes testing more useful, not supplementing blindly. Adequate protein intake is the more consistently recommended step.
The bottom line
The largest recent analysis found no clinical evidence that collagen supplements prevent or treat skin aging, and the apparent benefits in the pooled data disappeared once independently funded and higher quality trials were isolated. The industry disputes that, and the dispute is worth knowing about. Biotin helps if you are deficient, which is uncommon, and can distort thyroid testing, which is worth flagging to your clinician.
The supplements that reliably earn their place are the ones correcting a shortfall someone has actually measured. That is a smaller category than the shelf suggests, and it is the one worth spending on.
This article is for general education and is not medical advice.