As men get older, changes in energy metabolism, muscle function and overall physical performance can become more noticeable. At the same time, scientists have become increasingly interested in NAD+, a molecule involved in cellular energy metabolism and several processes associated with healthy aging.

NMN (nicotinamide mononucleotide) is a naturally occurring compound and a precursor to NAD+. Because NAD+ levels and metabolism change with age, NMN has attracted attention as a potential nutritional approach to supporting healthy aging.

But what does current research actually tell us about NMN and men's health?


1. Supporting Energy Metabolism and Daily Vitality

NAD+ plays an important role in the way cells convert nutrients into usable energy. It participates in metabolic reactions that help cells produce ATP, the primary energy currency used by the body.

As we age, NAD+ metabolism changes, which has led researchers to investigate whether NAD+ precursors such as NMN could help maintain cellular energy metabolism.

Human studies have shown that NMN supplementation can increase NAD+-related metabolites in the blood. Some clinical trials in older adults have also reported improvements in selected measures related to physical function, sleep or fatigue, although results have not been consistent across all studies.

This means NMN is an interesting area of research for men who want to maintain energy metabolism and an active lifestyle as they age, but it should not be considered a treatment for persistent fatigue.


2. Supporting Muscle Function and Physical Performance

Maintaining muscle function becomes increasingly important with age. Muscle strength and physical performance can influence mobility, exercise capacity and independence in later life.

NAD+ is involved in cellular energy production and mitochondrial function, while NAD+-dependent enzymes such as sirtuins are involved in a variety of cellular processes related to metabolism and stress responses.

Some human research has specifically examined NMN in older men. In one randomized, placebo-controlled study, daily NMN supplementation increased NAD+-related metabolites and was associated with changes in certain measures of physical performance, including walking speed and grip strength. However, the researchers also noted that larger and longer studies are needed to confirm these findings.

Therefore, current evidence is better described as support for research into healthy muscle function and physical performance, rather than proof that NMN can prevent muscle loss or treat age-related muscle disorders.

Regular resistance exercise, adequate protein intake, sufficient sleep and overall nutrition remain fundamental for maintaining muscle health.


3. NAD+ and Healthy Aging

One reason NMN has attracted so much scientific interest is its relationship with NAD+.

NAD+ is involved in several cellular processes beyond energy metabolism. It participates in reactions involving mitochondrial function, cellular stress responses and DNA damage responses. NAD+-dependent proteins, including the sirtuin family, are also being studied for their role in cellular metabolism and healthy aging.

Another important NAD+-dependent enzyme family is PARP, which participates in cellular responses to DNA damage.

These mechanisms provide a scientific basis for studying NAD+ metabolism during aging. However, it is important to distinguish biological mechanisms from proven human outcomes.

Increasing NAD+ levels with NMN does not automatically mean that DNA repair, longevity or other aspects of aging will improve in humans. Researchers are still investigating how changes in NAD+ metabolism translate into meaningful long-term health outcomes.


4. NMN and Cardiometabolic Health: An Area of Ongoing Research

NAD+ metabolism is also being studied in connection with vascular and metabolic function.

Laboratory and animal research has suggested that NAD+-dependent pathways may interact with mechanisms involved in endothelial function, mitochondrial activity and cellular stress responses. Early human studies have explored whether NMN supplementation can influence markers related to vascular or metabolic health.

However, the clinical evidence is still limited. Current research does not establish NMN as a treatment for high blood pressure, cardiovascular disease, diabetes or other medical conditions.

For older men, the most established ways to support cardiovascular and metabolic health remain regular physical activity, a balanced diet, healthy body weight, adequate sleep and appropriate medical care.


What About Testosterone?

Testosterone naturally changes with age, which is one reason men's hormonal health often becomes a topic of interest after 40.

NAD+ and sirtuin-related pathways are involved in cellular and metabolic processes that may interact with hormone-related biology. However, there is currently not enough high-quality human evidence to conclude that NMN supplementation increases testosterone or improves male fertility.

For this reason, NMN should not be promoted as a testosterone booster.

Men experiencing symptoms such as persistent low libido, erectile difficulties, unexplained loss of strength or other significant changes should discuss them with a healthcare professional rather than assuming that they are simply a result of aging.


What Do We Know About NMN So Far?

Research into NMN and NAD+ metabolism is developing rapidly. Human studies have demonstrated that NMN can increase NAD+-related metabolites, but whether these biochemical changes consistently translate into meaningful improvements in health or physical performance remains an open question.

For men over 40, the most reasonable way to view NMN at present is as an emerging area of healthy-aging research, particularly in relation to NAD+ metabolism, cellular energy and physical function.

It is not a replacement for exercise, a balanced diet, adequate protein, quality sleep or appropriate medical care.


The Bottom Line

NMN is attracting attention because of its role as an NAD+ precursor and the important functions of NAD+ in cellular metabolism.

Current human research provides interesting evidence for further investigation, particularly around NAD+ metabolism, energy-related processes and physical function in older adults. At the same time, evidence remains insufficient to claim that NMN can prevent aging, increase testosterone, prevent muscle loss or treat cardiovascular and other diseases.

As research continues, larger and longer-term clinical trials will help clarify which potential benefits of NMN are meaningful for healthy aging in men.