NAD+ shows genuine biological promise for hair growth, but the honest state of the science is this: almost all the positive evidence comes from lab dishes and mice, with only a single small human trial published so far. The connection between NAD+, cellular energy, and hair follicle health is real and well-supported at the molecular level. What remains unproven is whether raising your NAD+ levels through supplements actually translates into thicker or more abundant hair on a human scalp. The gap between “biologically plausible” and “clinically demonstrated” is wide here, and the supplement market has comfortably leapt across it without waiting for the research to catch up.
Why Hair Follicles Are Energy Hungry
Hair follicles rank among the most metabolically active structures in the human body. Each follicle cycles through phases of rapid growth, regression, and rest, and the growth phase (called anagen) demands intense cell division and differentiation. All of that activity requires a steady supply of ATP, the molecule cells use as fuel. Mitochondria, the organelles that produce ATP, are central to keeping follicles running. Research has established that mitochondrial activity is especially critical during the transition from the resting phase into active growth, when follicle cells need a burst of energy to kick-start the process.
When mitochondria underperform, follicles struggle. Studies on dermal papilla cells, the specialized cells at the base of each follicle that orchestrate hair growth, show that boosting mitochondrial energy production promotes follicle activity. One study demonstrated that activating a mitochondrial enzyme in these cells significantly increased ATP production, and the follicles responded with enhanced growth.1Journal of Advanced Research. Activation of mitochondrial aldehyde dehydrogenase 2 promotes hair growth in human hair follicles This energy dependence is why NAD+ enters the conversation: it is a coenzyme that sits at the heart of mitochondrial energy production. Without adequate NAD+, mitochondria cannot efficiently convert nutrients into ATP.
The NAD+ Connection to Hair Follicle Health
NAD+ does not act on hair follicles the way a drug like minoxidil does, by directly widening blood vessels or extending growth phases. Instead, it works upstream, fueling the cellular machinery that keeps follicles healthy. NAD+ participates in hundreds of metabolic reactions, but two roles matter most for hair: energy production and the activation of proteins called sirtuins.
Sirtuins are enzymes that depend on NAD+ to function. They regulate a wide range of cellular housekeeping tasks, from repairing DNA damage to managing oxidative stress to maintaining mitochondrial health. In the context of hair, sirtuin activity has been shown to protect hair follicle stem cells from inflammatory damage. When researchers exposed hair follicle stem cells to an inflammatory signal, the cells lost viability and stopped dividing. But when Sirtuin-1 was overexpressed, it reversed these effects by restoring mitochondrial energy metabolism, reducing harmful reactive oxygen species, and blocking the cell-death pathway.2PubMed. Sirtuin‑1 protects hair follicle stem cells from TNFα-mediated inflammatory stress via activating the MAPK-ERK-Mfn2 pathway Broader research on stem cell biology confirms that NAD+-dependent sirtuins, including SIRT2, SIRT3, and SIRT7, govern a protective program in stem cells that prevents age-related decline.3Trends in Cell Biology. Mitochondrial regulation of stem cell aging and tissue degeneration
Separately, research on hair follicle mesenchymal stem cells found that when SIRT1 was knocked down, cells accumulated more oxidative stress, sustained more DNA damage, and showed increased signs of aging and cell death, all accompanied by drops in both NAD+ and ATP levels.4Springer Link / Stem Cell Reviews and Reports. PBX1-SIRT1 Positive Feedback Loop Attenuates ROS-Mediated HF-MSC Senescence and Apoptosis The pattern across these studies is consistent: when NAD+ or sirtuin activity drops, hair follicle cells suffer. When they are restored, the cells recover.
What Goes Wrong in Androgenetic Alopecia
Pattern hair loss, the most common type of thinning in both men and women, has traditionally been understood as a hormone-driven process where DHT (dihydrotestosterone) miniaturizes follicles over time. That hormonal story is accurate but incomplete. Research increasingly points to mitochondrial dysfunction as a key pathological feature of the condition. Dermal papilla cells from balding scalp tissue show reduced mitochondrial respiratory activity, higher levels of reactive oxygen species, and altered expression of mitochondrial regulators, including SIRT3.5Genetics and Molecular Research. MITOCHONDRIAL DYSFUNCTION OXIDATIVE STRESS AND THE NAD/SIRTUIN AXIS IN ANDROGENETIC ALOPECIA: EMERGING MECHANISMS AND THERAPEUTIC IMPLICATIONS
DHT appears to actively damage mitochondria in these cells. In a mouse model of androgenetic alopecia, DHT markedly reduced CYP19A1 (aromatase) expression and increased inhibitory factors, while also impairing mitochondrial respiratory capacity and morphology. A mitochondria-targeted antioxidant called MitoQ reversed these effects, reducing mitochondrial reactive oxygen species and improving respiratory function.6PubMed. MitoQ upregulates CYP19A1 to protect dermal papilla cells from DHT-induced mitochondrial dysfunction and apoptosis in androgenetic alopecia This suggests that the hormonal damage and the energy damage are intertwined, and that approaches targeting mitochondrial health could address a dimension of hair loss that conventional anti-androgen treatments like finasteride do not touch.
That said, while NAD+ precursors and sirtuin-regulating agents have shown positive outcomes in preclinical models, the causal role of NAD+ depletion in human pattern hair loss is not fully demonstrated.5Genetics and Molecular Research. MITOCHONDRIAL DYSFUNCTION OXIDATIVE STRESS AND THE NAD/SIRTUIN AXIS IN ANDROGENETIC ALOPECIA: EMERGING MECHANISMS AND THERAPEUTIC IMPLICATIONS We know the cells are energy-starved. We know NAD+ is involved in the pathways that protect them. But proving that replenishing NAD+ in a living human scalp actually rescues miniaturizing follicles requires evidence that does not yet exist.
What the Lab and Animal Studies Show
The preclinical results are genuinely encouraging, which is part of why the hype has outpaced the evidence. A study testing NMN (nicotinamide mononucleotide, a direct NAD+ precursor) on mice with DHT-induced hair loss found that it reversed follicle atrophy, hair thinning, and hair sparsity, with results compared favorably to minoxidil.7PubMed Central. β-Nicotinamide Mononucleotide Promotes Cell Proliferation and Hair Growth by Reducing Oxidative Stress The mechanism appeared to involve reduced oxidative stress and promotion of cell proliferation, fitting neatly into the NAD+-sirtuin-mitochondria framework.
In cell culture experiments, a “Mito-Activator Complex” containing nicotinamide, nicotinamide riboside, and NAD+ itself (combined with a green tea compound called EGCG) increased ATP levels, mitochondrial content, and the expression of hair-growth-related proteins in human dermal papilla cells. The researchers confirmed the mitochondrial link by using an inhibitor that suppresses mitochondrial homeostasis: the complex rescued the inhibitor’s negative effects, establishing that its pro-growth activity ran through the mitochondrial pathway.8PubMed Central. Hair growth enhancement via mitochondrial activation by Mito-activator complex An earlier study found that an herbal extract stimulated dermal papilla cell proliferation at least partly by increasing NADH and ATP generation through improved mitochondrial membrane potential.9Biological and Pharmaceutical Bulletin. Hair Growth Promoting Effect of Hottuynia cordata Extract in Cultured Human Hair Follicle Dermal Papilla Cells
These results are consistent and they point in the same direction. But cells in a dish and shaved mice are not the same as a human scalp with years of progressive thinning. Mouse skin is structurally different, mouse hair cycles are faster, and the doses and delivery methods used in animal studies often do not translate directly to what a person can achieve by swallowing a capsule.
The Human Evidence So Far
As of mid-2025, only one published human study has directly examined NAD+ precursors for hair outcomes, and it is extremely small. Researchers gave fifteen middle-aged women 500 mg per day of NMN in tablet form for twelve weeks and measured hair diameter before and after. The results showed that hair diameter increased from roughly 75 micrometers to 79 micrometers. Two participants were excluded as statistical outliers, leaving the analysis based on just thirteen people with no control group taking a placebo. That is far too small and methodologically limited to draw firm conclusions from, though the direction of the finding aligns with what the preclinical work predicts.
A separate clinical trial took a somewhat different approach, testing a topical antioxidant regimen on scalp health. While not specifically an NAD+ study, this 24-week randomized, double-blind, placebo-controlled trial found that the antioxidant treatment significantly reduced hair shedding and increased total hair count compared to placebo.10PubMed. Scalp application of antioxidants improves scalp condition and reduces hair shedding in a 24-week randomized, double-blind, placebo-controlled clinical trial This matters because one of the key proposed mechanisms by which NAD+ would help hair is through reducing oxidative stress. The trial supports the idea that targeting oxidative damage at the scalp can improve hair outcomes, even if it does not confirm NAD+ specifically.
What the field lacks is the kind of large, well-controlled trial that would settle the question: a randomized study with hundreds of participants, a placebo arm, standardized photography, and hair counts over at least six to twelve months. Until that exists, any claim that NAD+ supplements grow hair in humans is getting ahead of the data.
Why NAD+ Drops With Age and Why That Matters for Hair
One reason the NAD+ story resonates with people experiencing age-related hair thinning is that NAD+ levels genuinely decline as you get older, and the mechanism behind this decline is well-characterized. An enzyme called CD38 is a major player. Research has shown that CD38 expression and activity increase with aging, and that CD38 is required for the age-related decline in NAD+ and the mitochondrial dysfunction that follows, working through a pathway that involves reduced SIRT3 activity.11PubMed Central. CD38 Dictates Age-Related NAD Decline and Mitochondrial Dysfunction through an SIRT3-Dependent Mechanism CD38 also degrades NMN itself, which complicates supplementation: if the enzyme that is depleting your NAD+ is also breaking down the precursor you are taking to replenish it, the efficiency of supplementation may be lower than expected, especially in older individuals.
This creates a plausible chain of events for age-related hair thinning. As CD38 rises, NAD+ falls. Lower NAD+ means less fuel for sirtuins like SIRT1 and SIRT3, which protect follicle stem cells from oxidative damage and keep mitochondria healthy. Mitochondrial function declines. Follicle cells lose their ability to produce enough energy for the demanding anagen phase, and hair gradually thins. Each link in that chain has experimental support, but the chain has not been tested end-to-end in human hair specifically.
Oral Supplements Versus Topical Application
Most people interested in NAD+ for hair are thinking about oral supplements, specifically NMN or NR (nicotinamide riboside). These are widely available and have been shown in human studies to raise blood NAD+ levels. But blood NAD+ levels and scalp tissue NAD+ levels are not the same thing. Whether orally consumed NMN or NR meaningfully increases NAD+ in the dermal papilla cells at the base of your hair follicles is an open question. The molecule has to survive digestion, enter the bloodstream, and then reach a specific tissue compartment in the skin in sufficient concentrations to affect follicle metabolism.
Topical delivery offers a more direct route. The Mito-Activator Complex tested in cell culture contained NAD+ and its precursors applied directly to the cells, and several cosmetic companies are now marketing scalp serums with nicotinamide or NMN as active ingredients.8PubMed Central. Hair growth enhancement via mitochondrial activation by Mito-activator complex The challenge is that NAD+ is a large, charged molecule that does not easily penetrate the skin barrier. Nicotinamide (the simpler vitamin B3 form) penetrates skin more readily, which is why it is a common ingredient in skincare. Whether enough of it converts to NAD+ at the follicle level to replicate the results seen in cell cultures remains unclear. Some newer formulations use nanoparticle delivery or dissolving microneedle patches to try to overcome the absorption barrier, but these are mostly in early development.
Safety of NAD+ Precursors
NR has been studied in controlled human trials at doses up to 1,000 mg per day and has generally been well-tolerated. In one randomized, double-blind, placebo-controlled trial of healthy overweight adults, the type, frequency, and severity of side effects were similar across the NR and placebo groups, with no serious adverse events and no reports of flushing (a common side effect of niacin, a different form of vitamin B3).12Scientific Reports. Safety and Metabolism of Long-term Administration of NIAGEN (Nicotinamide Riboside Chloride) in a Randomized, Double-Blind, Placebo-controlled Clinical Trial of Healthy Overweight Adults NMN has a shorter track record in human trials but has shown a similar safety profile in the studies completed so far.
The concern is not short-term side effects but long-term unknowns. NAD-boosting interventions are pharmacologically active, meaning they genuinely change cellular metabolism. But the benefits observed in human trials have been largely limited to changes in blood biomarkers rather than outcomes that directly matter to patients, and long-term safety, including cancer risk and cardiovascular outcomes, has not been established.13PubMed Central. NAD⁺ Injections and “NAD Boosters”: Public Health Risks, Adverse Effects, and Regulatory Implications in the Context of Rapid Consumer Adoption Some researchers have raised theoretical concerns that boosting NAD+ could fuel the growth of existing tumors, since cancer cells are also metabolically hungry. This has not been demonstrated in human supplementation studies, but the possibility underscores why long-term data is needed before treating NAD+ precursors as categorically safe for years of daily use.
Common Misconceptions About NAD+ and Hair
The marketing around NAD+ supplements tends to conflate different levels of evidence in ways that mislead consumers. A few points worth clarifying:
- Lab results are not clinical results. When a product page says “shown to promote hair growth,” check whether the study involved human heads or cells in a petri dish. Most of the positive NAD+ hair data comes from cell cultures and mice, which is a meaningful starting point for research but not evidence that the product works on your scalp.
- NAD+ and niacin are not interchangeable. Standard niacin (nicotinic acid) and nicotinamide are inexpensive vitamin B3 forms that participate in NAD+ metabolism, but they raise NAD+ less efficiently than NMN or NR and come with different side-effect profiles. The flushing associated with niacin does not occur with NR or NMN.
- Higher doses do not necessarily mean more hair benefit. Because CD38 also degrades NAD+ precursors, simply increasing the dose may hit diminishing returns. The dose-response relationship for scalp tissue specifically has not been studied at all.
- NAD+ is not a substitute for proven hair loss treatments. Minoxidil and finasteride have decades of large-scale clinical trial data behind them. NAD+ precursors do not. If you are experiencing significant hair loss, starting with unproven supplements while skipping established treatments means losing time during which follicles may continue to miniaturize irreversibly.
Where the Research Is Headed
Several research threads are converging that could accelerate progress. The identification of CD38 as both the driver of age-related NAD+ decline and a degrader of NMN has made it a target for combination therapy: some researchers are exploring whether CD38 inhibitors given alongside NAD+ precursors could dramatically improve the effectiveness of supplementation.11PubMed Central. CD38 Dictates Age-Related NAD Decline and Mitochondrial Dysfunction through an SIRT3-Dependent Mechanism Others are investigating whether mitochondria-targeted antioxidants like MitoQ could be combined with NAD+ boosters to hit both the energy production and oxidative stress pathways simultaneously in androgenetic alopecia.6PubMed. MitoQ upregulates CYP19A1 to protect dermal papilla cells from DHT-induced mitochondrial dysfunction and apoptosis in androgenetic alopecia
The cosmetics industry is also investing heavily in topical delivery systems for NAD+ and its precursors, with formulations specifically designed for the scalp entering the market well before the clinical data justifies their claims. This is a pattern familiar from the broader anti-aging supplement space: the commercial applications outrun the science, consumers become unpaid test subjects, and researchers struggle to fund the controlled trials that would answer the basic questions because the products are already being sold without regulatory approval for hair-loss claims. Whether a well-designed, adequately powered human trial of NAD+ precursors for hair growth will emerge in the next few years depends largely on whether a supplement or pharmaceutical company sees enough commercial potential to fund one, since academic grants for hair research remain relatively scarce compared to the scale of consumer demand.