NAD+

A coenzyme central to cellular energy metabolism (mitochondrial electron transport, glycolysis, fatty-acid oxidation) and substrate for sirtuin deacetylases, PARP DNA-repair enzymes, and CD38. NAD+ levels decline measurably with age across most tissues including skin, correlating with mitochondrial dysfunction and reduced repair capacity. Topical NAD+ aims to replenish the cutaneous pool — but the molecule is large (663 Da), polar, and notoriously poor at penetrating the stratum corneum. Many cosmetic NAD+ formulations actually deliver precursors (nicotinamide riboside, nicotinamide mononucleotide) that convert intracellularly, with their own penetration profiles.

1–5% (precursor or stabilised NAD+ form)

Often paired with peptides and exosomes in longevity-positioned formulas.

Topical bioavailability of NAD+ is still under active research — claims should be specific and clinical, not general.

The topical-bioavailability gap is the central scientific honesty issue — most peer-reviewed work supporting NAD+ benefits is oral/intravenous, and the assumption that topical application replenishes the same cellular pools is not yet established. 'NAD+' on a label often means a precursor or a stabilised analogue, rarely the molecule itself. The longevity-skincare category is currently the highest signal-to-noise ratio target for overclaim.

The flagship 'longevity skincare' active — sold by Augustinus Bader, Estée Lauder Re-Nutriv, and a cohort of biotech-clean brands as the bridge between metabolic-aging science and topical skincare. Real value depends entirely on the specific molecule used and its delivery system; current-generation formulations are largely first-attempt.