A popular longevity supplement may have a new use: your hair. In what appears to be the first human trial of NMN (nicotinamide mononucleotide) for hair, growing-phase hair density rose from about 56 to about 88 hairs per square centimeter in 12 weeks. That is roughly a 57% jump. But there was no placebo group, and that changes how much weight the number can bear.
What the study actually did
The paper, published in Cosmetics in 2025 (12(5):204), comes from Fukumoto and colleagues. The authors are linked to Mitsubishi Corporation Life Sciences, which makes an NMN ingredient.
The design was simple:
- Type: single-arm, pre-post pilot (everyone got NMN; there was no comparison group)
- Participants: 15 healthy Japanese women aged 40-50
- Duration: 12 weeks
- Intervention: oral NMN made by Torula yeast fermentation, reported at 500 mg per day
- Measurements: TrichoScan analysis of the hair growth cycle, scanning electron microscopy (SEM) of the hair shaft and cuticle, hair metabolites and hormones, and visual analog scale (VAS) questionnaires
The 500 mg figure comes from an interview the company gave to trade press. The same company's consumer product reportedly recommends 250 mg per day, so the trial dose is not the same as the retail dose.
The headline numbers
| Measure | Before | After | Significance |
|---|---|---|---|
| Anagen (growth-phase) hair elongation density | 55.9 hairs/cm² | 87.7 hairs/cm² | p = 0.03 |
| Hair diameter | 75.3 µm | 78.8 µm | p < 0.01 |
The density change is large on paper. The diameter change is much smaller, about 3.5 µm or roughly 5%, but it was statistically stronger. Thicker strands and more hairs in the growth phase would point the same way if they held up in a controlled trial.
The researchers also reported:
- Better cuticle condition on SEM imaging
- Metabolomic shifts in amino acids and energy metabolism in hair
- No marked change in hair hormone levels
- Subjective gains in elasticity, gloss and volume, along with less perceived fatigue and less perceived hair loss
Why NMN, and why hair?
NMN is a precursor to NAD+, a molecule involved in cellular energy metabolism. NAD+ levels decline with age, which is the main reason NMN has become a staple of the longevity-supplement world. Hair follicles are metabolically busy and cycle through growth, regression and rest. The idea is that supporting follicle energy metabolism could favor the growth phase.
The metabolomic changes in amino acids and energy pathways fit that story. They do not prove it. The paper reports associations in a small group, not a demonstrated mechanism. The absence of hormone changes does suggest the effect, if real, is not working through the hormonal routes targeted by conventional hair-loss drugs.
The big caveat: no placebo
This is the part to take seriously before spending money.
- No control group. Without a placebo arm, there is no way to separate the effect of NMN from seasonal variation in hair shedding and growth, regression to the mean, measurement variability, or expectation effects.
- Tiny sample. Fifteen people is a pilot, not a verdict.
- Industry link. The authors are tied to an NMN supplier. That does not invalidate the data, but it is a reason to wait for independent replication.
- Narrow population. Healthy women aged 40-50 only. The study did not test men, older or younger women, or people with diagnosed hair-loss conditions.
- Not a baldness trial. It did not examine male-pattern baldness, and nothing here supports claims about reversing it.
- Subjective outcomes. The VAS improvements in gloss, volume and fatigue are self-reported and open to placebo effects, especially since participants knew they were taking the supplement.
- Short duration. Twelve weeks says little about whether gains persist or what happens after stopping.
Hair counts can also shift for reasons unrelated to any treatment, so a 57% change in a single-arm study should be read as a signal worth testing, not a measured treatment effect.
Practical takeaways
Dose: The trial used 500 mg per day of Torula yeast-fermented NMN. The sponsor's consumer product reportedly suggests 250 mg per day. No study has established a hair-specific optimal dose, so the trial dose is the only human reference point.
Timing: The study ran 12 weeks, so any realistic evaluation would need at least that long, given hair's slow growth cycle. The paper as summarized here does not establish a best time of day.
Who it might interest: Healthy women in their 40s who are curious about hair quality and already comfortable with NMN as a general supplement. Treat it as an experiment, not a proven treatment.
Who should skip it, or ask a clinician first:
- Anyone looking for a proven fix for pattern baldness or medically diagnosed hair loss, because this trial does not address those conditions
- Anyone whose hair loss is sudden or patchy, which warrants a medical workup for thyroid, iron and other causes
- Pregnant or breastfeeding women, and people on medications or with chronic conditions, who should get medical advice first, since this study did not evaluate those groups
- Anyone expecting dramatic results based on one uncontrolled pilot
The bottom line
The first human NMN hair trial produced eye-catching numbers: denser growth-phase hair, slightly thicker strands, healthier-looking cuticles and happier participants. It is also a 15-person, single-arm, industry-linked pilot with no placebo. The honest reading is that NMN for hair is an interesting hypothesis that now has a first human data point. A randomized, placebo-controlled trial with a larger and more varied group is needed before anyone can say it works.
