Can an NAD+ precursor move a biological-age measure? On NR, muscle clocks read lower

In human studies, three biological-age measures came out in the NAD+ precursor’s favor. Five months of nicotinamide riboside (NR) was associated with lower skeletal-muscle epigenetic age, in data from three independent human studies (Heikkinen 2026). In a 60-day randomized trial of 80 adults, a blood biological-age score held steady on NMN while it rose on placebo (Yi 2023), and in a 10-week pilot of 20 older adults with mild cognitive impairment, NR raised blood NAD+ 2.6-fold alongside lower epigenetic age on two clocks (Orr 2024). These studies lasted five months or less, and none tested lifespan.

Where the number comes from

The leading result comes from skeletal muscle in three independent human studies. Measured with seven epigenetic clocks, five months of NR supplementation was associated with reduced muscle epigenetic age acceleration, most clearly on the PCHannum, MEAT and DunedinPACE clocks, while four to six weeks of high-intensity interval training (HIIT) moved some clocks the other way, notably raising pace of aging on DunedinPACE (Heikkinen 2026). Changes in muscle mitochondrial content correlated with changes on the MEAT clock after NR, and after six weeks of HIIT (Heikkinen 2026).

Epigenetic clocks turn DNA-methylation patterns into a measure of biological age (Duan 2022).

The abstract reports an association, gives no participant numbers and does not describe a randomized design, and the authors say further studies are needed. That is the main limit on this number.

What it means for you

A 2021 systematic review of 156 publications shows why these clocks get attention: faster blood-based clocks were linked with mortality, cardiovascular disease, cancer and diabetes, and a higher body mass index, male sex and HIV infection were linked with faster clocks (Oblak 2021). The four clocks with enough data for statistical analysis, Horvath, Hannum, Levine and GrimAge, tended to agree in the direction of effects but varied in size. So the direction of a change is more consistent across clocks than its size.

The precursor trials that measured biological age point the same way. In a 60-day randomized, double-blind, placebo-controlled trial of 80 healthy middle-aged adults on 300, 600 or 900 mg of NMN a day, blood NAD+ rose in every NMN group at day 30 and day 60 versus placebo and baseline. Blood biological age, on the Aging.Ai 3.0 calculator, rose significantly on placebo and stayed unchanged in every NMN group at day 60, a significant difference from placebo; insulin resistance (HOMA-IR) did not differ (Yi 2023).

In a 10-week randomized, placebo-controlled pilot in 20 older adults with mild cognitive impairment, NR escalated to 1 g a day raised blood NAD+ 2.6-fold. In an exploratory analysis of blood cells, it was associated with a modest rise in DNA methylation and a reduction in epigenetic age on the PhenoAge and GrimAge clocks, while cognitive scores, the trial’s primary outcome, stayed stable (Orr 2024).

In a twin study, 20 BMI-discordant identical-twin pairs took an escalating 250 to 1000 mg of NR a day for five months. NR improved systemic NAD+ metabolism, muscle mitochondrial number and gut microbes, and modulated the epigenetic control of gene expression in muscle and fat; body fat and metabolic health did not improve (Lapatto 2023).

The rest of the evidence

Two reviews set the context. One notes that, as of 2023, most NMN studies had been done in cells or animals and a dozen human NMN trials were underway (Song 2023). Another describes the classic clocks, Horvath, Hannum, PhenoAge and GrimAge, as practical tools for evaluating interventions, and names the lack of higher-quality information as a major challenge (Duan 2022).

On the biology, DNA methylation is the most studied epigenetic mark, and prediction models using a small number of age-linked sites can accurately predict a person’s chronological age; a third review names this pattern the epigenetic clock, alongside “epigenetic drift” (Jones 2015). In mice, 12 months of oral NMN mitigated age-associated physiological decline during normal aging (Mills 2016); that is mouse data, not evidence in people.

The human studies, by grade

Study	Design	People	Dose / Duration	Result	Grade
Heikkinen 2026	Analysis of 3 human studies	Skeletal muscle from three independent studies; n not given	NR, dose not given, 5 months; HIIT 4-6 weeks	Muscle epigenetic age lower with NR (PCHannum, MEAT, DunedinPACE); HIIT moved some clocks the other way	B
Lapatto 2023	Twin study	20 BMI-discordant identical-twin pairs	NR 250-1000 mg/day, escalating, 5 months	NAD+ metabolism, muscle mitochondria and gut microbes improved; body fat and metabolic health did not	B
Yi 2023	RCT	80 middle-aged healthy adults	300/600/900 mg NMN, 60 days	Blood NAD+ rose; blood biological age held on NMN, rose on placebo	A
Orr 2024	Pilot RCT	20 older adults with MCI	NR escalated to 1 g/day, 10 weeks	Blood NAD+ up 2.6-fold; PhenoAge/GrimAge age down; cognition stable	B
Oblak 2021	Systematic review	156 publications; 57 relationships analyzed	Not applicable	Four blood clocks agree in direction, vary in size; faster clocks linked with higher mortality	A

Put together: every trial here that measured blood NAD+ found it rose, and the biological-age readings came out in the precursor’s favor in muscle, in blood cells and on a blood biological-age calculator. Among the biological-age results, only the NMN one is reported as a significant difference from placebo; the nicotinamide riboside clock results are an association across three studies and an exploratory outcome in a 20-person pilot.

Next step

If these clocks and this NAD+ finding have you comparing precursors, our piece on how NMN and NR both raise NAD+ in people keeps it to the human trials: https://healthspanpost.com/articles/how-do-nmn-and-nr-become-nad-in-human-trials-both-raised-blood-nad/