Human Study Finds Blood NAD+ Levels Do Not Decline in Older Adults, Challenging Key Claims

In coverage updated October 16, 2026, the New Zealand Herald highlighted a 2026 study reporting stable blood NAD+ levels in old age. The report paired that finding with a warning from Aladdin Shadyab of the University of California, San Diego: no drug or supplement has been shown to extend human lifespan.

The Central Result

According to NutraIngredients, the NAD+ study involved more than 300 people across independent cohorts and found no meaningful association between whole-blood NAD+ and age. The report also described no major changes after the diet or exercise interventions studied. For longevity research, this challenges a common marketing premise: that aging predictably produces low blood NAD+ that should routinely be replenished. Its immediate relevance is to the rationale behind that claim rather than evidence of longer life or better health.

Human Evidence

The NAD+ study was conducted in humans using whole-blood samples across independent cohorts.

NutraIngredients describes participants spanning younger and older adults as well as elite athletes. The cohorts also included frail older adults taking part in diet or exercise interventions and people receiving nicotinamide riboside, or NR. These groups brought different ages and intervention backgrounds into the research. The reported headline finding concerned the relationship between whole-blood NAD+ and age across the cohorts studied.

That detail matters when reading the coverage. “NAD+ levels” sounds like a single universal measurement, but the reported result refers specifically to whole blood. Keeping the sample type attached to the finding makes the scientific question clearer: did this blood measurement show a meaningful relationship with age? NutraIngredients reports that it did not.

The lifestyle findings address another question. In the interventions described by NutraIngredients, whole-blood NAD+ showed no major changes after diet or exercise interventions. Those observations belong alongside the age comparison rather than being merged into a general verdict about every intervention. Each result should retain the population and measurement to which it refers.

The Herald placed the study within a broader discussion of longevity marketing. Its coverage identified peptides and growth hormone alongside resveratrol and NAD+ among products promoted as ways to extend life. Shadyab's statement addressed the strength of demonstrated human lifespan evidence. That makes the promised endpoint central to interpreting the claim.

A lifespan claim asks whether people live longer. A healthspan claim asks whether they spend more time in good health. A biomarker claim concerns a measured biological feature. Keeping these questions separate helps prevent a result about a blood measurement from quietly becoming a claim about healthy years or survival.

Steven Austad told the Herald that extending healthspan is the primary aim for many aging researchers. Extra years of life may follow as a side effect rather than being the main objective. This distinction gives readers a more useful way to assess research than treating every aging-related result as a step toward longer life. AgeAmaze's discussion of years lived versus years lived well provides further context for that distinction.

The Herald also offered a historical illustration. It reported that U.S. life expectancy increased by about six months between 2009 and 2019 even as healthy life expectancy declined. The comparison shows why the two endpoints deserve separate attention. A discussion focused only on survival can leave the quality and health of those additional years out of view.

Sofiya Milman of the Albert Einstein College of Medicine added another concern in the Herald's coverage: much of what circulates in the longevity space is not science-based. Her warning places the burden on the evidence behind a particular promise. For readers, the useful question is not whether a product sounds connected to aging biology. It is whether the research addresses the outcome being advertised.

Where Evidence Stops

• Clinical outcomes were not established. The reported NAD+ finding concerns blood measurements and their relationship with age and specified interventions. It does not demonstrate that supplementation extends lifespan or healthspan. A change in a biomarker would also need evidence connecting it to a meaningful benefit before supporting that broader claim.
• Whole blood is a defined boundary. The result does not establish that NAD+ remains stable in every tissue or that every NAD+ measurement behaves the same way. The defensible conclusion stays attached to whole-blood NAD+ in the cohorts studied. It is not a finding that NAD+ is unimportant throughout the body.
• Association does not supply a mechanism. The reported absence of a meaningful age relationship does not explain every biological process involving NAD+. Nor does it establish why the measurements remained stable. The finding tests a proposed age pattern in blood rather than supplying a complete account of NAD+ and aging.
• Methods require closer scrutiny. The Herald's account does not provide study methods or limitations. The participant total reported by NutraIngredients gives useful context but is not enough on its own to assess how the result was obtained. Evaluating the original analysis would be necessary for a fuller judgment of the study's strength.
• An NR cohort is not an efficacy conclusion. NutraIngredients reports that the research included people receiving nicotinamide riboside. That inclusion alone does not establish a particular supplement benefit or lack of benefit. The reported absence of major changes after lifestyle interventions should not be reassigned to the NR group without a corresponding result.
• Resveratrol received no separate trial assessment. The Herald names it among products promoted for life extension but does not provide resveratrol-specific human trial evidence. Shadyab's statement about unproven human lifespan extension should not be expanded into a claim that resveratrol has no effects on any measured health outcome.
• Animal results remain a separate evidence category. The Herald notes that some compounds have extended lifespan in worms and mice. Those findings do not establish human lifespan extension. A product claim aimed at people needs evidence appropriate to people rather than a substitution of animal survival results for human outcomes.
• The coverage is not a safety review. The Herald's expert discussion does not provide a comprehensive assessment of supplement safety or indications. It therefore cannot serve as a basis for an individual regimen. Decisions about personal supplement use belong with a qualified healthcare professional who can assess the individual's circumstances.

The practical reading strategy is to identify the promise first. Is the claim about a blood measurement, a health outcome or longer survival? Then check whether the research actually measured that outcome. This keeps the assessment focused on evidence rather than the appeal of the product category.

For NAD+ coverage, retain the words “whole blood” when summarizing this result. For a life-extension claim, look for demonstrated human lifespan evidence. AgeAmaze's guide to assessing human findings behind NAD+ products offers a related reading framework without turning the distinction into a supplement recommendation.

The same discipline applies when a marketing explanation begins with an appealing biological pathway. The pathway is part of the argument to examine rather than the conclusion to accept. A useful companion is the distinction between a biological rationale and a clinical result. Keeping those stages separate allows an interesting finding to remain interesting without assigning it a benefit that has not been demonstrated.

The Next Test

The next useful phase is independently replicated human research connecting clearly defined NAD+ measurements with meaningful healthspan outcomes, with direct human lifespan evidence required wherever longer life is the claim.

How AgeAmaze helps

A stable blood NAD+ finding can become another overstated supplement message if its measurement is detached from the outcome being promised. AgeAmaze explains biomarkers and emerging interventions for research-minded adults, helping them assess longevity claims while keeping experimental findings separate from established health benefits and personal treatment advice.

Read the research

Sources

1. 6 things longevity experts wish people would stop saying
2. Catching up with healthspan and lifespan supplements