The core NAD+ biology — the mechanisms of decline, the sirtuin pathways, the DNA repair and mitochondrial functions that NMN supports — is the same in men as in women. What differs are several aspects of male physiology that intersect specifically with NAD+ metabolism and the downstream effects of sirtuin activation: the gradual decline in testosterone that characterizes male aging, the cardiovascular risk profile that makes men particularly vulnerable to certain age-related outcomes, and the fact that several of the most-cited NMN clinical trials enrolled predominantly or exclusively male populations, providing the most direct evidence base for NMN efficacy in men.
This article covers the considerations most relevant to men when thinking about a NAD+ supplementation protocol — not because NMN works differently for men, but because understanding the sex-specific context helps prioritize and interpret the evidence most directly applicable.
Contents
Testosterone Decline and the NAD+ Connection
Men experience a gradual decline in testosterone production from their late 20s onward — typically around 1–2% per year, with more pronounced effects becoming apparent by the 40s and 50s. This decline, sometimes called andropause or late-onset hypogonadism, contributes to reduced muscle mass and strength, increased visceral fat, lower energy and libido, impaired cognitive function, and mood changes. While less abrupt than female menopause, the cumulative effect of testosterone decline over decades is substantial.
NAD+ and testosterone metabolism intersect through several pathways. SIRT1 activation — downstream of elevated NAD+ — modulates the hypothalamic-pituitary-gonadal (HPG) axis that regulates testosterone production. Animal research has shown that SIRT1 activation in hypothalamic neurons supports LH (luteinizing hormone) pulsatility, which drives Leydig cell testosterone production in the testes. Whether NMN supplementation meaningfully supports testosterone production through this mechanism in aging men has not been studied in human trials — the research is primarily animal-based — but the mechanistic pathway is coherent.
Testosterone itself supports NAMPT expression in muscle tissue, creating a reciprocal relationship: adequate testosterone supports NAD+ synthesis capacity, and adequate NAD+ supports the sirtuin activity that influences testosterone regulation. As both decline in aging men, each deficit compounds the other. NMN cannot replace testosterone where true hypogonadism exists, but supporting the NAD+ system that modulates the HPG axis may help maintain testosterone at the higher end of the range consistent with the individual’s age-related trajectory.
For men with clinically low testosterone who are considering testosterone replacement therapy (TRT), NMN is a complementary rather than competing consideration — the two address different aspects of the hormonal and metabolic changes of male aging. Discussing both with a prescribing physician is appropriate for men managing testosterone decline medically.
Cardiovascular Risk: Where Men Face the Greatest Urgency
Men develop cardiovascular disease on average a decade earlier than women — the loss of estrogen’s cardiovascular protection at menopause brings women’s risk closer to men’s in later life, but men face elevated risk earlier and for longer. The specific cardiovascular changes most relevant to middle-aged men — arterial stiffening, endothelial dysfunction, elevated inflammatory markers, and increasing blood pressure — are precisely the domains where NAD+ precursor supplementation has some of its strongest human evidence.
The Martens et al. (2018) NR trial enrolled both men and women but found particularly clear effects in participants with elevated baseline arterial stiffness and blood pressure — a population predominantly represented by middle-aged men in cardiovascular risk cohorts. The NAD+-eNOS-nitric oxide pathway that supports endothelial vasodilation is directly relevant to the endothelial dysfunction that precedes cardiovascular disease in men.
The Yi et al. (2023) GeroScience physical performance trial enrolled middle-aged and older adults with a mixed-sex population, finding significant improvements in grip strength, walking endurance, and fatigue reduction at 1,000 mg/day NMN alongside exercise. The functional improvements in this trial — directly relevant to the sarcopenia and physical performance decline that accelerates in middle-aged men — represent some of the strongest human evidence for NMN’s functional benefits.
For men with established cardiovascular risk factors — elevated blood pressure, dyslipidemia, metabolic syndrome, or a family history of early cardiovascular disease — the cardiovascular evidence for NAD+ supplementation provides specific and directly applicable rationale beyond the general longevity argument. The complete cardiovascular evidence is covered in the article on NAD+ and cardiovascular health.
Muscle Mass, Strength, and Physical Performance
Sarcopenia — the age-related loss of muscle mass and strength — begins earlier in men than is commonly recognized, with meaningful muscle mass decline occurring from the late 30s onward and accelerating after 60. Muscle is one of the highest NAD+-demand tissues in the body, and the relationship between NAD+ decline and sarcopenia runs through multiple mechanisms: reduced mitochondrial efficiency in muscle cells, impaired PGC-1α-driven mitochondrial biogenesis, and declining insulin sensitivity that impairs amino acid uptake and muscle protein synthesis.
The Yoshino et al. (2021) trial’s demonstration of improved skeletal muscle insulin sensitivity in response to NMN is relevant for men as well as women — insulin resistance in muscle is a mechanism of sarcopenia that accelerates with age regardless of sex. The Yi et al. trial’s physical performance findings specifically support NMN’s utility for maintaining functional physical capacity in aging men.
For men who exercise regularly — which the research strongly supports as the foundation of any muscle preservation strategy — NMN may augment the exercise-driven AMPK and PGC-1α activation through the NAD+-SIRT1 pathway, potentially producing more robust mitochondrial biogenesis than exercise alone. The article on exercise and NAD+ covers how these mechanisms interact.
Metabolic Health and Insulin Resistance
Men are disproportionately affected by central obesity and visceral fat accumulation, which is a primary driver of the insulin resistance and metabolic syndrome that accelerates NAD+ depletion through CD38 upregulation and chronic inflammation. The metabolic case for NMN is therefore often more immediately applicable in middle-aged men with metabolic risk factors than in women of equivalent age, where the metabolic transition tends to be more gradual until the menopause-associated shift.
For men with elevated fasting glucose, HbA1c trending upward, unfavorable lipid profiles, or growing waist circumference, NAD+ precursor supplementation at 500–1,000 mg/day is a mechanistically well-grounded addition to a metabolic health protocol. Berberine — as an AMPK activator with established clinical evidence for blood glucose and lipid improvement — is a particularly relevant complementary addition for this population, covered in the article on berberine.
The Male-Predominant Trial Evidence
Several of the most-cited NMN and NR human trials enrolled predominantly male populations, which is worth noting when evaluating evidence relevance:
The Irie et al. (2020) foundational pharmacokinetics and safety trial enrolled only healthy adult men. The Elhassan et al. (2019) NR muscle biopsy trial enrolled older men. The Dollerup et al. (2018) NR metabolic trial enrolled obese men. The Martens et al. (2018) NR cardiovascular trial enrolled both sexes but skewed older and male in its cardiovascular risk subgroup.
This male predominance in the early trial literature means that for men, the evidence base is arguably more directly applicable than it is for women, where the Yoshino trial stands out as the primary female-specific evidence. The general NMN clinical evidence reviewed in the article on what human clinical trials on NMN actually show is, in substantial part, evidence in male populations.
Prostate Health Considerations
Prostate health is a specific concern for men as they age, and the relationship between NAD+ supplementation and prostate biology warrants mention. The theoretical concern about NAD+ supporting cancer cell metabolism applies to prostate cancer as it does to other cancers — men with active prostate cancer or men in active surveillance for low-grade prostate cancer should discuss NAD+ supplementation with their urologist or oncologist before starting.
For men without prostate disease, the SIRT1-mediated DNA repair and anti-inflammatory effects of NAD+ elevation are consistent with a cancer-protective rather than cancer-promoting role in normal prostate tissue. Whether NMN meaningfully affects prostate cancer risk in either direction in healthy men has not been studied in human trials. The cancer-related considerations for NMN generally are covered in the article on NMN and cancer: what the research says.
Dosing for Men
The general age-adjusted dosing framework applies to men:
- Under 40: 250–500 mg/day as a reasonable starting point; the deficit being corrected is smaller at this age and the functional improvement at higher doses is correspondingly less pronounced.
- 40–55: 500 mg/day as a solid standard dose; meaningful NAD+ decline is occurring and 500 mg has clinical trial support for functional effects in this age range.
- 55–65: 500–750 mg/day; NAD+ decline is more substantial and the case for higher doses strengthens.
- Over 65: 750–1,000 mg/day; the population where the Yi trial’s functional improvements were most pronounced, and where the CD38-driven NAD+ deficit is likely most significant.
For men with significant metabolic risk factors — central obesity, elevated fasting glucose, hypertension — starting at the higher end of the age-appropriate range is more appropriate than the conservative lower bound, given that metabolic dysfunction accelerates NAD+ depletion beyond what age alone predicts.
Frequently Asked Questions
The mechanistic pathway from NAD+ to testosterone through SIRT1-HPG axis modulation is coherent and supported by animal data, but human clinical evidence directly demonstrating that NMN supplementation raises testosterone in aging men is limited. NMN is not a testosterone replacement and should not be pursued as a primary treatment for clinically diagnosed hypogonadism. For men with symptoms of testosterone decline, a comprehensive evaluation by a physician — including testosterone blood testing — is the appropriate first step, with NMN as a potentially complementary addition to whatever treatment approach is indicated.
Does NMN affect sexual function in men?
No human clinical evidence specifically addresses NMN’s effects on sexual function in men. The mechanisms through which NMN might indirectly support sexual function — testosterone pathway support, improved endothelial NO production and vascular function, enhanced mitochondrial energy in reproductive tissue — are plausible but unconfirmed as clinically meaningful at supplemental doses. Some men taking NMN report subjective improvements in energy and vitality that they associate with better sexual function, but these reports are anecdotal and cannot be attributed specifically to NMN.
Is NMN more important for men or women?
The question cannot be answered definitively — both sexes experience NAD+ decline with age and both have strong mechanistic reasons to benefit from NAD+ precursor supplementation. The relative urgency differs by circumstance: women at menopause experience an acceleration of NAD+ decline that creates particular urgency in that transition period; men face earlier and more sustained cardiovascular risk that makes the cardiovascular NAD+ evidence particularly applicable. The most accurate answer is that NMN is relevant for both sexes across their respective aging trajectories, with different aspects of the evidence being most directly applicable to each.
Should men take NMN differently if they are also on TRT?
No established protocol exists for combining NMN with testosterone replacement therapy. The two interventions address different biological systems — NMN supports the NAD+/sirtuin pathway, TRT corrects hormonal deficiency — and there is no known negative interaction between them. However, TRT is a medically managed intervention, and adding NMN alongside it is a decision to discuss with the prescribing physician as part of an overall hormonal and metabolic health strategy rather than self-directing without medical awareness.