Blood NAD doesn't fall with age: what two new studies mean for NMN and NR

Does blood NAD fall with age? Two 2026 papers in Nature Metabolism measured NAD in human blood across the adult lifespan. Neither found a decline in healthy adults.

NAD (nicotinamide adenine dinucleotide) is a coenzyme that every cell uses in energy metabolism. NMN (nicotinamide mononucleotide) and NR (nicotinamide riboside) are related to vitamin B3, and cells convert them into NAD. A 2021 review in Nature Reviews Molecular Cell Biology describes ageing as accompanied by a gradual decline in tissue and cellular NAD in several species, including humans.

The short answer: in 1,068 adults in Lithuania, whole-blood NAD did not decline with age in healthy people. It stayed flat in men and rose slightly in women, and lower levels tracked cardiovascular disease and high blood pressure instead. That does not make NMN and NR pointless, because blood is not muscle, brain or skin. It does remove the simplest argument for taking them and puts the burden back on trials that show a benefit.

What the Lithuanian study measured

The study, with Diana Romenskaja-Avgul as first author and Dalius Ratautas as corresponding author, was published on 4 November 2026. The cross-sectional arm measured 1,068 adults (636 women and 432 men) in Lithuania between 2023 and 2025, once each, with a morning finger-prick blood spot after an overnight fast. Repeat samples in a small exploratory arm brought the total to 1,340 measurements. The laboratory measured total whole-blood NAD (NAD+ plus its reduced form, NADH). "Healthy" meant no self-reported chronic disease, no chronic-disease medication and no NAD or vitamin B3 supplement use. Pregnant or breastfeeding adults and people with blood-clotting disorders were excluded.

• Healthy men: no significant link between age and whole-blood NAD. The youngest men, aged 18 and 19, had higher levels than the rest, but there was no progressive decline.
• Healthy women: NAD rose with age, by about 0.07 µM a year in the main analysis (sensitivity analyses gave slopes such as 0.043). The authors call it a subtle effect that needed a large cohort to detect and say it had not been reported before.
• Sex: men had higher whole-blood NAD than women across the cohort.
• Disease: NAD was lower in people with cardiovascular disease and in people with hypertension, in both sexes. For women the comparison was adjusted for age. Dyslipidaemia showed no reduction, and the thyroid-disease group did not differ from healthy people. Type 2 diabetes, asthma, immune-mediated inflammatory disease and cancer groups had fewer than 15 people of each sex and were not analysed.
• Medication: everyone classified in a disease group was taking medication for that condition. In cardiovascular disease and hypertension, NAD was still lower.

The authors conclude that whole-blood NAD "tracks cardiovascular disease rather than chronological age". They also state that the study was not designed to show causation and that its findings should not be used to support NAD supplementation as a treatment for hypertension or cardiovascular disease.

A second study points the same way

Maria Trętowicz and colleagues at Amsterdam UMC published a separate study in Nature Metabolism in May 2026. Using mass spectrometry across seven human cohorts, they found that whole-blood NAD+ stayed stable with age and across lifestyle interventions, but did change with nicotinamide riboside supplementation. Its dedicated ageing comparison set 20 adults under 30 against 20 adults over 60. The Lithuanian authors describe their own result as replicating that finding at larger scale, with a different method and population. The Amsterdam work was funded by EU and national research grants, with one cohort supported by Nestlé Health Science, and its authors declare no competing interests.

What blood NAD can and cannot tell you

Whole-blood NAD comes almost entirely from red blood cells, so a blood result does not map neatly onto muscle, brain or skin. Earlier work reported lower NAD in those tissues, and the Lithuanian authors say their data do not contradict it. A comment on the paper by Stephen Gardell and Joseph Baur, published the same day, makes the same point: blood NAD gives an incomplete view of the body's NAD metabolism and misses differences between blood and solid tissues. It also says the blood data challenge the idea that lower systemic NAD causes age-related disease.

That leaves two separate questions. Does NAD fall with age in blood? In healthy adults, apparently not. Does it fall in the tissues people care about? That has been reported for some tissues, with far less human data.

The disclosures matter too. Several Lithuanian authors are or were employees of SensoLife, whose dried-blood-spot NAD kit was used, and of LifeLab1, the laboratory that ran the analysis; the study reports no specific funding, and Bloodo supplied the dried-blood-spot collection kits at no cost. Joseph Baur reports research funding and materials from Eli Lilly, Pfizer, Elysium Health and Metro International Biotech, consulting fees from Cytokinetics, and is an inventor on a patent on NAD precursors for liver regeneration. Stephen Gardell reports consulting fees from Sironax and Cytokinetics and is an inventor on a patent on NAMPT activators.

The main arm measured each person once. The paper lists its own limits: total NAD rather than NAD+ alone, no direct haematocrit measurement, possible medication effects, and few disease-free adults over 70.

What supplements do to blood NAD

Raising blood NAD is not the hard part. In an eight-week randomised trial in overweight adults, 100, 300 and 1,000 mg of NR a day raised whole-blood NAD+ by 22%, 51% and 142% within two weeks, with no significant difference in adverse events against placebo. Two authors, at Chromadex Spherix Consulting, are ChromaDex employees, Charles Brenner is the company's chief scientific adviser and an inventor of intellectual property it licenses, and ChromaDex funded the trial. In a randomised, open-label trial run by Nestlé researchers, 14 days of NR or NMN, but not nicotinamide, raised circulating NAD+ by a comparable amount in 65 healthy participants analysed.

The Lithuanian programme saw the same thing in real-world use. Six of 22 self-reported supplement users (27%) had whole-blood NAD of 38 to 58 µM, roughly two to three times the unsupplemented range, a level reached by only one of more than 1,000 unsupplemented people. In two volunteers who took 1,000 mg a day of self-purchased NMN, NAD rose from about 19 to 20 µM to about 51 to 56 µM, with a half-time of 3.2 to 4.3 days. Those are small, uncontrolled observations, and the authors label that part of the study exploratory.

Does a higher blood number do anything?

That is the question the trials have to answer, and so far the answers are modest. In the 24-week npj Aging trial, adults aged 65 and over took 1,250 mg of NMN or placebo every day. NMN raised NAD+ and related metabolites, but there was no significant improvement in the primary endpoint, auditory function, or in physical performance measures. Nominal changes in body composition, lipids and dietary behaviour did not survive correction for multiple testing. The supplement was generally well tolerated, although the authors say careful safety monitoring is warranted. The trial was funded by MIRAILAB BIOSCIENCE, which also supplied the NMN, and three authors are its employees.

The metabolic result comes from a 10-week randomised trial in 25 postmenopausal women with prediabetes who were overweight or obese: 13 took 250 mg of NMN a day and 12 took placebo. Insulin-stimulated glucose disposal and muscle insulin signalling increased after NMN and did not change after placebo. Muscle NAD+, blood pressure and physical function did not change. It is one small trial in one population, and two authors disclose NMN-related patent or licensing interests.

On blood pressure, a 2018 crossover trial of NR in healthy middle-aged and older adults concluded only that future trials should assess blood pressure and arterial stiffness.

Long-term safety is the open question

The Lithuanian authors write that the long-term consequences of sustained high NAD levels in humans are unknown, that most trials last weeks to months and are too small to detect rare or delayed effects, and that the largest long-term trial enrolled just ten patients. They add that NAMPT is an established cancer driver in laboratory research, that CD38 is raised in inflammatory disease and that NAD metabolism can drive pro-inflammatory changes in neuro-inflammation. They stress that these findings do not show high NAD is harmful, but raise safety questions that current research cannot answer.

Their overall conclusion is that the data "provide no broad rationale for NAD-boosting interventions" in healthy adults. They allow that condition-specific use in defined patient groups may retain a rationale, and they say adequately powered trials and long-term safety data are needed before broader conclusions can be drawn.

How to read NMN and NR marketing now

• "Your NAD declines with age" is not supported by blood data in healthy adults. A seller who uses the line should be able to cite a human measurement, not only an animal study.
• "Raises NAD" is true and is not the same as "works". The trials above show blood NAD rising on doses from 100 mg of NR upwards. They do not show better hearing, physical performance or vascular health in healthy older adults.
• Check who ran and paid for the trial a brand cites. Several of the human trials above were run or co-authored by company staff (ChromaDex employees, Nestlé researchers, MIRAILAB employees), so read the disclosures.
• A single blood-NAD result is a weak guide. Within-person readings varied by about 2 to 3 µM over a week in the Lithuanian data, and the study found no age-related deficit to correct.

The reasonable position is neither that NAD is a myth nor that NMN is proven. NAD matters, precursors raise blood levels dependably, and whether that helps healthy people is unproven. Pregnancy and breastfeeding were exclusion criteria in the Lithuanian study, and anyone pregnant, breastfeeding or taking regular medicines should speak to a doctor or pharmacist before starting any supplement.

Questions to ask before buying

• Which compound is it (NMN, NR, nicotinamide or NAD+ itself), and what is the daily dose?
• Does that dose match a dose used in a published human trial, and did that trial measure anything beyond blood NAD?
• Is the product authorised or registered in your country (see the section below)?
• Does the brand publish batch analysis from an accredited laboratory?

UAE rules

In Dubai, no health supplement may be manufactured, imported, advertised, sold or distributed unless it is registered in Dubai Municipality's Montaji system, and shoppers can check a product by scanning the barcode in the Montaji app. Federally, product registration has moved from the Ministry of Health and Prevention (MOHAP) to the Emirates Drug Establishment (EDE), which regulates food supplements. A registered supplement is still a supplement: registration does not mean it slows ageing or corrects NAD levels.

Tell your doctor or pharmacist about any supplement you take. If you have chest pain, severe breathlessness or collapse, call 998 for an ambulance, or 999 for the police.

FAQ

Does NAD decline with age?

In whole blood from healthy adults, a 1,068-person study found no decline: levels were flat in men and rose slightly in women. Declines have been reported in some tissues, such as muscle, brain and skin, and blood tests do not measure those.

Do NMN and NR raise NAD?

Yes, in blood. An NR trial showed dose-dependent rises within two weeks, and NMN trials show a rise within about two weeks at the doses used. Whether that translates into a health benefit in healthy adults has not been shown.

Does any trial show NMN slows ageing?

None of the trials above shows that. In the 24-week trial in adults aged 65 and over, 1,250 mg of NMN a day produced no significant improvement in the primary endpoint, auditory function, or in physical performance measures.

Is low blood NAD a sign of heart disease?

In the Lithuanian study, lower whole-blood NAD was associated with cardiovascular disease and hypertension. The study cannot show that low NAD causes either condition or that supplements treat them.

How do I check an NMN or NR product in Dubai?

Scan the barcode in Dubai Municipality's Montaji app to see whether the supplement is registered. Registration is a check on the product, not evidence that it works.