NAD+ is the molecule that carries them. Research asks what happens when its supply changes with age, and whether that can be altered.
NAD+ · Redox coenzyme
Cells turn food into usable energy through chains of chemical reactions. Many of those steps involve moving electrons, tiny charged particles, from one molecule to another. NAD+ is the carrier that accepts and hands on those electrons. Tissue levels appear to fall with age, so researchers ask whether restoring them changes how cells work. The evidence comes mainly from cells, rodents and small human trials of precursor molecules.
Nicotinamide adenine dinucleotide, NAD+, is not a peptide. It is a coenzyme, a helper molecule that enzymes need in order to work, and it is present in every living cell. Its central job is electron transfer. NAD+ accepts electrons released when fuel such as glucose is broken down and becomes NADH. NADH then donates those electrons to the respiratory chain in the mitochondria, which uses the energy to make ATP, the cell’s energy currency, and NAD+ is regenerated for the next round. (NADH made outside the mitochondria hands its electrons across through shuttle systems; the molecule itself does not simply cross the inner membrane.)
NAD+ is also consumed, rather than recycled, by a second group of enzymes. Sirtuins, which help regulate metabolism, and PARPs, which take part in DNA repair, each break NAD+ apart as they act. Cells therefore rebuild it continuously from precursors such as nicotinamide, nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN). Most published work on raising NAD+ concerns those precursors, not NAD+ itself, and the distinction matters when reading any claim.
The background observation is a gradual decline in tissue NAD+ with age, reported in rodents and in human samples, and reviewed by Covarrubias and colleagues (2021). That review links the decline to age-associated conditions in animal models and states plainly that whether repletion helps ageing humans, and whether it is safe, remains to be learnt. Rajman, Chwalek and Sinclair (2018) summarise the animal evidence for NAD-boosting molecules.
Human studies have mostly used oral precursors. Trammell and colleagues (2016) showed that single oral doses of NR raised blood NAD+ metabolites in healthy volunteers, in a trial sponsored by the NR supplier. Yoshino and colleagues (2021) ran a ten-week randomised, placebo-controlled trial of oral NMN in postmenopausal women with prediabetes and measured muscle insulin sensitivity, which improved, without reporting broader clinical outcomes.
Direct administration of NAD+ itself has been studied far less. Grant and colleagues (2019) followed plasma and urine chemistry in a small pilot group during a six-hour intravenous NAD+ infusion. Plasma NAD+ did not rise for the first two hours, suggesting rapid removal and breakdown, and the study measured metabolites, not any health outcome. No medicine containing NAD+ is approved for an age-related indication in Australia or elsewhere.
Because NAD+ is essential does not mean that supplying more of it does anything useful; a molecule can be indispensable and also already sufficient. Findings for oral NR or NMN cannot be transferred to NAD+ given by another route, or the reverse, because the molecules are handled differently in the gut, blood and cell. The infusion pilot showed that NAD+ is broken down quickly in plasma, leaving open how much reaches cells intact. Human trials to date are short, small and measure blood or muscle chemistry rather than function or lifespan, and several are industry-funded. Long-term effects of sustained NAD+ elevation have not been established in people.
NAD+ is not listed by name in the current Poisons Standard (June 2026) and no NAD+ medicine is approved in Australia for an age-related or energy indication.
Sources and status checked 2026-09-22
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