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Research

NAD+ Precursors

Nicotinamide riboside and NMN reliably alter NAD-related biomarkers, but human trials have not established broad improvements in function, disease prevention, or longevity.

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Emerging
Evidence rating
Evidence review

What the evidence says

Nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) are vitamin B3-related precursors intended to raise nicotinamide adenine dinucleotide, a cofactor involved in energy metabolism and cellular signaling. Raising a blood metabolite is target engagement, not proof of rejuvenation.[1]

A six-week crossover trial in 24 healthy middle-aged and older adults found that NR raised NAD-related metabolites and was generally tolerated, with exploratory blood-pressure and arterial-stiffness signals. The sample was too small and short to establish cardiovascular protection.[1]

In insulin-resistant men with obesity, 12 weeks of NR raised NAD metabolites but did not improve insulin sensitivity, glucose metabolism, lipid accumulation, or body composition. A small mild-cognitive-impairment trial found biochemical changes without a significant improvement in cognition.[2][3]

Meta-analyses of NR and NMN trials do not show a consistent improvement in muscle mass, strength, physical function, glucose control, or lipid outcomes. Different compounds, doses, assays, and enrolled populations should not be collapsed into a single proven anti-aging effect.[4][5]

Potential benefits

  • Reliably raises selected NAD-related metabolites, confirming oral bioavailability and biological activity.[1]
  • Provides a useful human research tool for testing whether NAD biology translates into clinical benefit.[3][5]

Side effects and cautions

  • Short trials report mostly mild gastrointestinal symptoms, headache, fatigue, or no clear excess, but are underpowered for rare harms.[2][5]
  • Long-term high-dose safety, medication interactions, and effects in cancer or major organ disease remain uncertain.[4]
How we scored it

Evidence breakdown

Short randomized trials demonstrate bioavailability and generally acceptable near-term tolerability, while clinical outcomes are inconsistent, small, and product-specific.

Read our full methodology
Clinical relevanceLow

Most studies prioritize NAD metabolites and short-term surrogate outcomes rather than disability, disease, or survival.

Study qualityModerate

Randomized placebo-controlled trials exist, but they are usually small and brief.

Safety dataLow

Near-term trial safety is reassuring; chronic high-dose use and diverse older populations remain under-studied.

References

Full source list

  1. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults

    Nature Communications · 2018

  2. Nicotinamide riboside supplementation is not associated with altered methylation homeostasis or insulin sensitivity in obese men

    American Journal of Clinical Nutrition · 2018

  3. Nicotinamide riboside supplementation in mild cognitive impairment: a randomized controlled trial

    GeroScience · 2024

  4. The Effect of Nicotinamide Mononucleotide and Riboside on Skeletal Muscle Mass and Function: A Systematic Review and Meta-Analysis

    Journal of Cachexia, Sarcopenia and Muscle · 2025

  5. Effects of Nicotinamide Mononucleotide on Glucose and Lipid Metabolism in Adults: A Systematic Review and Meta-analysis of Randomised Controlled Trials

    Current Diabetes Reports · 2024

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