Writing in Cosmetics, the researchers reported significant improvements in both anagen hair elongation density and hair diameter.
Anagen is the phase of active hair growth which can last about two to eight years and determines the length of hair growth.
An increase in anagen hair elongation density refers to the increase in hair growth length.
However, contrary to the researchers hypothesis, there was also a significant decrease in total hair count post-NMN supplementation.
A total of 15 healthy Japanese women aged between 40 and 50 years took part in the single-arm, pre-post intervention study.
They orally ingested 500mg of a NMN supplement provided by Mitsubishi Corporation Life Sciences around the breakfast time for 12 weeks.
The NMN supplement used was a torula yeast-fermented NMN produced in Japan.
To evaluate the effects of NMN on hair health, hair density was examined using TrichoScan, SEM imaging analysis, as well as via a subjective questionnaire.
Key findings
A key finding was that NMN supplementation has led to a significant increase in hair length growth at the anagen phase, based on TrichoScan analysis.
Three days after shaving, anagen hair elongation density - or hair length growth - had significantly increased from 55.9 ± 43.5 hairs/cm2 at baseline to 87.7 ± 21.9 hairs/cm2 post-supplementation.
Terminal hair density three days after shaving also increased significantly from 38.6 ± 33.7 to 66.2 ± 15.1hairs/cm2.
Terminal hair refers to hair with a diameter of at least 40 µm, based on TrichoScan’s definition of hair types.
Aside from anagen hair and terminal hair, there are two other hair types: telogen hair which refers to non-growing hair and vellus hair which refers to fine hair with a diameter of less than 40 µm.
On the other hand, mean hair diameter also grew significantly from 75.3 ± 7.6 μm at baseline to 78.8 ± 9.7 μm post-supplementation.
However, total hair density saw a significant reduction where it dropped from 190.8 ± 34.0 to 167.9 ± 35.8 hairs/cm2.
“Contrary to our hypothesis, a significant decrease in hair count was observed after taking NMN.
“Although we cannot deny the possibility that the decrease in hair count is due to taking NMN, we speculate that it is due to seasonal hair loss.
“Previous studies among Japanese populations have confirmed seasonal variations in hair shedding, peaking in September due to summer UV damage,” the researchers wrote.
This study took place during 12 September to 5 December last year.
NMN’s potential
Still, the researchers noted that the significant improvements in anagen hair elongation indicated that NMN supplementation may enhance follicle maturation and nutrient supply to dermal papilla cells.
This could in turn promote the growth of existing terminal hairs, rather than stimulating new vellus hair - or fine hair - formation.
“This could lead to improved hair volume and texture through strengthening and thickening existing hair, potentially attributable to enhanced scalp conditions and follicular cell functions.
“SEM analysis revealed thicker hair shafts and improved cuticle conditions, consistent with TrichoScan findings,” the researchers wrote.
Subjective findings
Based on self-administered visual analog scale (VAS) questionnaire findings, significant improvements were observed for fatigue and gray hair perception post-supplementation.
There were also significant improvements in hair parting concerns, hair loss upon waking and shampooing, as well as hair elasticity, combing ease, gloss, and volume.
Energy metabolism
In addition, NMN intake had led to significantly increased levels of metabolites related to energy metabolism - a process which could be related to hair health.
The metabolites that were increased include isovalerylcarnitine, creatine, creatinine, leucine, and isoleucine.
The findings suggest that NMN supplementation could support mitochondrial ATP production and amino acid metabolism.
Mitochondrial ATP production is noteworthy when it comes to hair health as mitochondrial dysfunction has been reported in the pathogenesis of androgenetic alopecia (AGA), the researchers wrote.
“In line with a previous animal study, the TricoScan analysis in this study demonstrated an increase in terminal hair density following NMN supplementation.
“These findings indicate that NAD+, through its ability to enhance the sirtuin pathway and mitochondrial function, plays an important role in hair growth and the prevention of hair loss.
“Therefore, oral NMN supplementation may represent a promising strategy for maintaining healthy hair,” they wrote.
