Nicotinamide Adenine Dinucleotide (NAD+) is an essential coenzyme found in every cell, playing a central role in numerous biological processes. This molecule is fundamental to energy production and the maintenance of cellular health and function. Because NAD+ levels naturally decline with age, it has garnered significant attention in longevity and aging research. This interest has extended to its potential effects on highly regenerative processes, leading to investigations into the relationship between NAD+ and hair growth.
The Role of NAD+ in Cellular Energy
NAD+ is widely recognized for its participation in redox reactions, cycling between its oxidized form (NAD+) and its reduced form (NADH) to carry and donate electrons. This electron transfer is a foundational step in cellular respiration, where NAD+ acts within the mitochondria to convert nutrients into adenosine triphosphate (ATP), the primary energy currency of the cell. Without sufficient NAD+, cells cannot function efficiently, leading to an energy deficit.
Tissues with high metabolic demand, such as the constantly dividing cells of the hair follicle, require a substantial supply of ATP to maintain rapid turnover. The decline of NAD+ levels observed with aging is linked to reduced cellular repair and compromised function. This reduction suggests that energy-intensive processes, like hair growth, may become impaired due to an inability to meet the high metabolic requirement.
NAD+ Influence on the Hair Growth Cycle
The hair follicle is one of the most metabolically active tissues, cycling through distinct phases: the growth phase (anagen), the regression phase (catagen), and the resting phase (telogen). NAD+ supports this cycle by acting as a required cofactor for specialized enzymes, particularly sirtuins and Poly(ADP-ribose) polymerases (PARPs). These NAD+-dependent enzymes regulate cellular stress response and DNA repair, processes highly active in the rapidly dividing hair follicle stem cells (HFSCs).
Sirtuins, such as Sirt1 and Sirt7, are activated by NAD+ and regulate the lifespan and regeneration of these stem cells. Maintaining high NAD+ levels protects HFSCs from oxidative stress and accumulated DNA damage that can lead to premature aging of the follicle. When DNA damage occurs, PARPs rapidly consume NAD+ to facilitate repair. This consumption can deplete NAD+ reserves and compromise the energy needed for growth. By supporting these protective mechanisms, sufficient NAD+ may help prolong the active anagen phase and prevent the follicle from prematurely shrinking or entering the telogen phase.
Scientific Findings and Current Research
Research exploring the effects of NAD+ on hair growth focuses on NAD+ precursors, such as Nicotinamide Mononucleotide (NMN) and Nicotinamide Riboside (NR), which the body converts into NAD+. Preclinical studies, primarily in mouse models, have shown promising results. Boosting NAD+ levels can reverse hair follicle atrophy and reduce hair thinning. In some animal studies, NMN administration helped restore hair follicle size and reduced thinning caused by dihydrotestosterone (DHT), a hormone associated with common hair loss.
These animal findings suggest that enhanced NAD+ levels may promote the growth of existing terminal hairs by enhancing follicle maturation and nutrient supply to the dermal papilla cells. A small-scale human clinical trial involving middle-aged women who took 500 mg of NMN daily for 12 weeks provided preliminary evidence of a benefit. The study reported a significant increase in both hair diameter and the elongation density of hairs in the active growth (anagen) phase, suggesting a positive impact on hair quality and thickness.
While these results suggest that NAD+ enhancement may be a strategy for maintaining healthy hair, the current evidence is preliminary and limited in scope. Larger, double-blind, placebo-controlled studies are necessary to confirm the efficacy of NAD+ precursors as a treatment for common forms of hair loss, such as androgenetic alopecia.
Practical Applications and Usage Considerations
People aiming to increase their NAD+ levels typically use oral supplements containing precursors like Nicotinamide Mononucleotide (NMN) or Nicotinamide Riboside (NR). These precursors are efficiently converted into the functional NAD+ molecule. For NMN, dosage in clinical studies and common consumer use ranges from 250 mg to 900 mg per day.
For Nicotinamide Riboside (NR), the typical daily dosage is between 250 mg and 500 mg, though studies have safely used up to 1000 mg. Topical formulations are also being developed to deliver the compound directly to the scalp and hair follicles, but data on their efficacy is still emerging. These precursors are generally well-tolerated, but side effects can occasionally include mild gastrointestinal issues.
Before starting any new supplement regimen, it is important to consult with a healthcare professional. A physician can help determine the appropriate dosage based on individual health status and ensure that supplementation does not interfere with existing medications or health conditions.