Oral Supplementation of Nicotinamide Mononucleotide (NMN) Improves Hair Quality and Subjective Perception of Hair Appearance in Middle-Aged Women

Background: Nicotinamide mononucleotide (NMN) has gained attention as an anti-aging compound due to its ability to replenish NAD+ levels, which typically decline with age and stress. While improvements in skin conditions have been reported, clinical studies on human hair remain lacking. In this study, we evaluated the effects of NMN supplementation on hair conditions in middle-aged women and explored its association with quality-of-life (QOL) factors such as fatigue. Methods: Torula yeast-fermented NMN was evaluated in this clinical trial. A single-arm, pre-post intervention study was conducted involving 15 healthy Japanese women aged between 40 and 50 years who orally consumed NMN for 12 weeks. Hair growth cycles and hair shaft diameters were assessed using TrichoScan (TrichoGrabV3B) analysis and scanning electron microscopy (SEM). Hair metabolites and hormone levels were also measured. Subjective indices, including fatigue and hair texture, were evaluated using a visual analog scale (VAS) questionnaire. Results: Following NMN supplementation, anagen hair elongation density (hairs/cm2) significantly increased from 55.9 to 87.7 (p = 0.03). Hair diameter (µm) also significantly increased from 75.3 to 78.8 (p < 0.01), with improvements in hair cuticle condition. Metabolomic analyses revealed significant changes in amino acids and energy metabolism-related compounds. No marked changes were observed in hair hormone concentrations. The VAS questionnaire indicated improvements in subjective hair characteristics such as elasticity, gloss, and volume, as well as reductions in fatigue and perceived hair loss, suggesting enhanced QOL. Conclusions: Oral supplementation with NMN may be a beneficial strategy for promoting hair growth and improvement in hair cuticle condition in middle-aged women, thus potentially enhancing overall hair care and quality of life.