Whole-Blood NAD Did Not Decline With Age in Healthy Adults, Study Finds

On November 4, 2026, Vilnius University researchers and collaborators published “Whole-blood NAD levels track cardiovascular disease but not chronological age” in Nature Metabolism. The research was conducted in Lithuania between 2023 and 2025.

What did the study find about aging?

Among healthy participants, whole-blood NAD did not significantly decline with age in men and increased modestly with age in women. The researchers also found lower whole-blood NAD associated with cardiovascular disease, particularly hypertension. For longevity research, the central finding challenges the assumption that healthy aging necessarily involves a declining blood NAD measurement. It shifts the question toward what that measurement reflects across different people and health states rather than treating it as a simple indicator of age-related depletion.

Was this NAD study conducted in humans?

This was a human study, not an animal experiment or an in vitro study.

The Nature Metabolism paper reports 1,340 measurements from 1,068 adults in its main cohort. That cohort included 636 women and 432 men. The central age findings concerned healthy participants and were reported separately for women and men. Those distinctions matter because the headline result brings together several different comparisons within the same research project.

The authors used dried blood spots to measure total whole-blood NAD, meaning NAD+ plus NADH. That is the laboratory measurement behind the findings about age and cardiovascular disease. It is also the measurement reported in the supplement observations. Keeping that definition consistent makes it easier to follow the paper without changing the meaning of “NAD” between one result and the next.

Why did the findings differ between women and men?

In healthy women, the researchers estimated an increase of about 0.07 μM per year. They described the increase as subtle. Healthy men showed no statistically significant age-associated decline. These are separate findings rather than a single pattern that applies identically to everyone in the cohort.

In Vilnius University's account of the research, lead researcher Dalius Ratautas said the increase in women was unexpected. He emphasized the importance of adequately representing women and analyzing results separately by sex. For readers assessing longevity research, this is a useful example of why a study's overall headline should be read alongside its subgroup findings.

The editorial lesson is to preserve those distinctions when discussing the result. “No decline in healthy men” and “a modest increase in healthy women” describe the evidence more accurately than a blanket statement that NAD is unaffected by age. The finding makes sex-specific analysis part of the scientific question rather than a secondary detail.

What did the cardiovascular comparison show?

The researchers reported lower whole-blood NAD in participants with cardiovascular disease, particularly hypertension. This finding concerned health status rather than chronological age alone. It therefore raises a different research question from the comparison between younger and older healthy participants.

Keeping those questions separate helps explain the paper's significance. A blood measurement might differ between groups defined by disease even when it does not show the expected pattern across age groups. The study places both observations in view without requiring them to be treated as the same biological story.

What happened among people using NAD supplements?

The paper discusses NMN and nicotinamide riboside (NR) as NAD precursors. In its real-world comparison, 22 people reported using NAD boosters: 10 men and 12 women. The authors found higher NAD among users than among non-users. Among those users, 6 had measured concentrations between 38 and 58 μM.

The authors also reported a separate observation involving two people using NMN. After a five-day baseline, measured NAD rose during 14 days of self-administered use. Their measurements increased from about 19 to 20 μM at baseline to 51 to 56 μM during use. This observation was distinct from the comparison of supplement users within the main cohort.

These results give readers several findings to keep separate: the age comparison among healthy participants, the cardiovascular disease comparison and the supplement observations. Each addresses a different question. Interpreting them requires matching the conclusion to the particular comparison that produced it.

What limits the conclusions?

• The age analysis was cross-sectional. Participants in the main age analysis were sampled once, so the researchers compared people of different ages rather than following the same people over decades. The estimated slope in women describes an association across participants, not an observed annual increase within each woman. Read it as a population pattern rather than an individual aging trajectory. For broader context, AgeAmaze's guide to assessing biomarker study designs provides a framework for distinguishing these questions.
• Whole blood does not directly represent every tissue. The authors explicitly say their findings do not contradict reports of age-related NAD decline in particular tissues such as muscle, brain or skin. A result from blood and a result from another tissue need not follow the same pattern. The practical boundary is to keep “whole-blood NAD” in the conclusion rather than replacing it with a claim about NAD throughout the body.
• The assay has measurement limits. Total NAD combines NAD+ and NADH without preserving the blood's native ratio between them. The authors also identify limitations in the blood-spot method and possible effects of differences in hematocrit. These details matter when deciding exactly what the reported concentration represents. Treat the result as a finding from this measurement approach rather than assuming that all NAD tests provide interchangeable information.
• The cardiovascular association does not establish cause and effect. The study could not determine whether disease lowers NAD or whether lower NAD contributes to disease. The authors also identify medication as a possible contributor to differences between disease groups. The finding therefore supports further investigation rather than using NAD supplements to prevent or treat hypertension or cardiovascular disease. Personal decisions about blood pressure or supplement use belong with a qualified clinician.
• Disease-free adults over 70 were represented only to a limited extent. The authors identify this as a weakness when interpreting patterns in healthy aging. Results from the available participants should not be extended automatically to the oldest healthy adults. Better representation of that group would help test how broadly the observed age patterns apply.
• The supplement observations were not controlled efficacy tests. The main-cohort comparison relied on self-reported use and was observational, so it cannot establish that supplements caused the difference between users and non-users. The separate NMN observation involved only two people and was self-directed rather than a clinical efficacy trial. Keep these designs separate from a controlled study intended to establish an intervention's effects.
• A higher blood NAD result is not a demonstrated healthspan benefit. The study did not test whether supplementation improves health, slows aging or extends lifespan. The authors say the findings do not provide a broad rationale for NAD-boosting interventions in healthy adults. When considering a supplement claim, separate evidence that a blood measurement changes from evidence that a meaningful health outcome improves. That distinction also guides interpretation of the broader human evidence on NAD supplements.
• Long-term consequences remain unresolved. The paper notes that the consequences of sustained high NAD in humans remain unknown. As broader context, The Conversation's review reports that NR and NMN can raise blood NAD while meaningful long-term health and lifespan benefits remain unestablished. It also describes inconsistent human results on healthy-aging outcomes. A changed laboratory value therefore needs to be judged separately from long-term safety and clinical benefit.

What research should come next?

The next phase should follow people over time, distinguish blood measurements from tissue-specific biology and use controlled trials with clinical outcomes to test whether changing NAD improves healthspan.

How AgeAmaze helps

Deciding whether a whole-blood NAD result justifies a supplement claim is an evidence question, and AgeAmaze addresses it through clear reporting on biomarkers and emerging interventions. For adults facing overstated biological-age and supplement claims, the publication explains mechanisms and study quality so that established findings remain separate from promising or speculative ideas.

Read the research

Sources

1. A Study by VU Researchers Reveals Unexpected Results
2. Can NAD+ supplements help us age more healthily? Here's what ...
3. Whole-blood NAD levels track cardiovascular disease but not chronological age - Nature Metabolism