NAD precursors: exposure and training function
In this investigation
- A positive runner trial measured cycling thresholds
- A newer athlete trial raised NAD but missed its primary outcome
- Higher exposure did not deliver better lifting tests
- An insulin-clamp null remains a useful counterexample
- A 2026 combination result did not isolate an NR benefit
- What would resolve the young-training question?
Nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) help make nicotinamide adenine dinucleotide (NAD), a cellular coenzyme. Do they improve function alongside training?
A positive runner trial measured cycling thresholds
A six-week study randomized 48 recreational runners aged 27–50, all completing, to NMN at 300, 600 or 1,200 mg/day or matching powder placebo. Everyone followed running/cycling training: 40–60 minutes, 5–6 times weekly.
Selected ventilatory-threshold results during cycling favored NMN, particularly the higher exposures. VO₂max and peak workload did not improve relative to placebo. These physiological thresholds are distinct from a faster running race, better sprints or increased lifting strength. NAD was not measured, and the muscle mechanism was inferred. Statistical methods included post-hoc comparisons, without an identified correction across the full outcome collection.
A Chinese government grant funded the work; GeneHarbor supplied powders. Authors declared no conflicts. Original runner trial, 2021
A newer athlete trial raised NAD but missed its primary outcome
The 2025-online/2026-issue collegiate-athlete trial randomized 219 men to placebo, 500 mg/day NMN, paprika xanthophyll extract, or both for eight weeks. Only 139 entered the per-protocol analysis, with smaller measurement-specific samples.
Blood NAD increased with NMN. The reported primary eight-week NMN-versus-placebo lactate-threshold, lactate-accumulation and heart-rate outcomes were null. Four-week and lower-baseline-NAD combination findings were exploratory and uncorrected; the primary analysis used a step-down procedure. They do not establish an effective combination or a personal NAD threshold. The extract also differs from my bell pepper.
Training volume changed during camps, and diet changes were not measured. Ezaki Glico funded the work; all authors were employees and disclosed a related patent application. Original athlete trial
Higher exposure did not deliver better lifting tests
A 28-day trial randomized 30 overweight/obese adults aged 45 or older, 21 to a microcrystalline β-NMN product, MIB-626, and nine to placebo. The research exposure was 1,000 mg twice daily; usual activity continued. Two did not complete; imaging had additional technical losses.
Blood NAD increased, while muscle NAD and phosphocreatine recovery measurements did not significantly improve. Chest/leg-press strength, repetitions to failure, stair-climbing power and aerobic performance did not differ significantly. Selected weight, lipid and blood-pressure changes were nominal findings. The short, small study was powered around exposure and safety, so it cannot rule out smaller or longer-term effects.
Metro International Biotech funded it; several authors held company employment, consulting or equity interests. Original physiologic trial, 2023
An insulin-clamp null remains a useful counterexample
A twelve-week trial assigned 40 sedentary men aged 40–70 with obesity to 1,000 mg NR twice daily or matching placebo. All completed, but two final clamps failed technically.
The primary insulin-sensitivity result was null (interaction P=.71), despite increased urinary NAD-related metabolites. Body composition and measured glucose/lipid oxidation did not improve. A changed excretion measurement therefore does not establish useful metabolism or training gains.
Research grants supported the work; ChromaDex supplied capsules. One author disclosed advising the supplier, stock and research support. This NR result need not match every NMN experiment. Original clamp trial, 2018
A 2026 combination result did not isolate an NR benefit
In Friedreich’s ataxia, 66 people aged 10–40 were randomized across NR/placebo and exercise/attention-control combinations for twelve weeks; 65 supplied the primary exercise outcome. NR exposure was weight-based, 300–900 mg/day. Training included three aerobic and two resistance sessions weekly.
NR plus exercise increased peak oxygen uptake versus inactive control: 0.21 L/min, 95% CI 0.05–0.36, Holm-adjusted P=.0299. Crucially, adding NR did not significantly outperform exercise alone: 0.05 L/min, CI −0.10 to 0.21, P=.49. NR alone was also null versus control. This tests disease-specific low fitness, not healthy lifting or cognition.
Adverse events were mild/moderate. NIH and FARA supported it; ChromaDex donated product and could check the manuscript for proprietary information. Authors disclosed industry relationships. Original factorial trial, 2026
What would resolve the young-training question?
A completed MIB-626 exercise study in healthy, highly fit adults aged 19–40 directly targets this gap, including physical and cognitive outcomes. Its current official record has no posted results. Completion and planned cognitive testing cannot establish benefit.
These findings establish no reliable supplement benefit for my present routine. Research exposures are study descriptions.
The longevity frontier develops other clinical populations; the niacin dossier explains ordinary intake references.