NAD⁺ has become one of the most discussed molecules in longevity science.
It is essential for cellular energy production and is involved in DNA repair, cellular stress responses and other processes that become increasingly important as we age.
This has led to a simple and appealing idea:
If NAD⁺ changes with age, could increasing it help us age more slowly?
The biology is promising. But what has actually been proven in humans?
What Is NAD⁺?
NAD⁺ stands for nicotinamide adenine dinucleotide.
It is present in cells throughout the body and plays a central role in converting nutrients into cellular energy. It is also required by enzymes involved in DNA repair, cellular signaling and responses to metabolic stress.
Changes in NAD⁺ metabolism have been associated with aging, although the relationship is complex. NAD⁺ levels can differ between tissues, and age-related changes are not identical throughout the body.
This makes NAD⁺ an important target in aging research — but not yet a proven measure or treatment of aging.
How Can NAD⁺ Be Increased?
One approach is to provide compounds the body can use to produce NAD⁺.
Two of the most widely studied are:
NMN — nicotinamide mononucleotide
and
NR — nicotinamide riboside.
Both are NAD⁺ precursors.
NAD⁺ itself is also offered intravenously by some longevity and wellness clinics.
These approaches should not be treated as equivalent. They have different routes of administration and, importantly, very different levels of clinical evidence.
Do NMN and NR Actually Increase NAD⁺?
This is where the human evidence is relatively clear.
A 2026 systematic review examined 33 human intervention studies, including 28 randomized trials.
Across the studies, oral NMN and NR consistently demonstrated biochemical target engagement. In practical terms, supplementation increased circulating or cellular NAD-related metabolites.
So there is good evidence that these precursors can influence NAD⁺ biology in humans.
But this answers only the first question.
Changing NAD⁺ biology is not the same as slowing aging.
Do Higher NAD⁺ Levels Improve Health?
Here the evidence becomes much less consistent.
Human studies have investigated outcomes including physical function, metabolic health, vascular function and other measures potentially relevant to healthy aging.
Some studies have reported positive effects.
Others have found little or no meaningful difference.
Overall, the results remain heterogeneous and often specific to individual outcomes or populations.
This means that a measurable increase in NAD-related biomarkers should not automatically be interpreted as evidence that a person is aging more slowly.
What About the Animal Research?
Preclinical research is considerably more encouraging.
In animal models, increasing NAD⁺ availability has been associated with improvements in metabolic function, mitochondrial biology, inflammation and some measures of physical function.
These findings are an important reason why NAD⁺ remains such an active area of longevity research.
But animal studies answer a different question from human clinical trials.
An intervention can improve aging-related biology in laboratory animals without ultimately producing the same clinical benefits in people.
Does Increasing NAD⁺ Slow Human Aging?
We do not yet know.
Current human evidence demonstrates that NMN and NR can influence NAD⁺ biology.
There are also promising signals for particular health and functional outcomes that deserve further investigation.
But we do not yet have evidence demonstrating that increasing NAD⁺:
slows the overall biological aging process,
delays multiple age-related diseases,
extends healthspan,
or increases human lifespan.
That distinction is fundamental.
A successful longevity intervention ultimately needs to do more than change a biomarker. It needs to produce meaningful and reproducible improvements in human health and function over time.
