NAD+: what it does, why it falls with age, and what the trials actually found

Before you read onResearch and educational information for adults, not medical advice. This entry explains one longevity term — what it means, why it matters and what the evidence says — and nothing here diagnoses, treats, cures or prevents any condition. Baseline labs come before anything, and your own physician has the final word. Longevity Bros offers coaching and written research protocols only — we do not sell, supply, source or ship any compound.

What it means

Nicotinamide adenine dinucleotide is a coenzyme found in every cell. In its oxidised form (NAD+) it accepts electrons from fuel; as NADH it hands them to the mitochondria to make ATP. It is also consumed by enzymes that repair DNA (PARPs), by the sirtuins, and by CD38, an enzyme that rises with inflammation and burns through NAD+ faster as we age.

Tissue NAD+ falls with age — by perhaps half between twenty and eighty in skin and muscle, though the human data are thinner than the claims. Precursors that the body converts into NAD+ include NMN, nicotinamide riboside (NR), niacin and tryptophan.

Why it matters for longevity

Lower NAD+ means less efficient mitochondria, slower DNA repair and quieter sirtuins — three of the hallmarks of ageing in one molecule. Restoring it in old mice improves muscle, vascular function and metabolic markers, which is why NAD+ became the most heavily marketed longevity molecule of the last decade.

What the evidence says

Precursors raise blood NAD+ reliably: NR 1 g/day raised it by about 60% in six weeks (Martens 2018). The downstream results are modest. Martens found no change in blood pressure, arterial stiffness or exercise capacity. Dollerup 2018 (NR 2 g/day, 12 weeks, obese men) found no change in insulin sensitivity or mitochondrial respiration. Yoshino 2021 (NMN 250 mg/day, 10 weeks, prediabetic women) found improved muscle insulin sensitivity and nothing else. A 2023 trial of NMN 900 mg/day reported a small gain in walking distance.

NAD+ infusions have no published controlled trial. The reported "energy" effects are uncontrolled, and infused NAD+ is largely broken down before it enters cells. The CD38 mechanism suggests that lowering inflammation may do more for NAD+ than taking a precursor.

How to measure or use it

Whole-blood NAD+ is measurable through specialist labs; reference ranges are wide and the relationship to tissue NAD+ is loose.
The levers with evidence for raising the NAD+/NADH ratio: exercise, an overnight fast, body-fat reduction and lower chronic inflammation (hs-CRP).
If a precursor is trialled, the honest endpoints are the ones the trials used — insulin sensitivity, walking distance, subjective energy — over 8–12 weeks, then a decision.

NAD+ (research page) — what the research compound is studied for
NAD+ IV and injections — the infusion claims, graded
Mitochondria and energy — the trials, tabulated, and the exercise comparison

Frequently asked questions

NMN or NR — which is better?

Both raise blood NAD+. NR has more published trials; NMN has the Yoshino insulin-sensitivity result. Neither has outcome data that separates them.

Do NAD+ drips work?

They raise blood NAD+ transiently. No controlled trial has shown a benefit, and much of the infused molecule is degraded before it reaches cells.

Does exercise raise NAD+?

Yes — training raises NAMPT, the enzyme that recycles NAD+, in muscle, and improves the NAD+/NADH ratio. It is the best-evidenced lever.

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