NAD+

NAD+ is a molecule every cell needs to turn food into usable energy, and whose measured levels in tissue fall with age — the observation the whole NAD-boosting supplement market rests on. It also serves as fuel for several repair enzymes, which is why a decline in it is an attractive explanation for several features of aging at once.

The commercial logic is a chain of three steps. Levels fall with age; a supplement can raise them; therefore raising them should undo some of what aging did. The first two steps have support. The third is the one being sold, and it is the one that has not been demonstrated.

Supplements do not contain NAD+ itself, which is poorly absorbed. They contain precursors, most commonly nicotinamide mononucleotide (NMN) or nicotinamide riboside (NR), which the body converts. Trials confirm that these raise NAD+ in blood, and that is a genuine pharmacological finding rather than a marketing claim.

Whether a higher reading changes anything a person would notice is a separate question with its own answer. A 2026 meta-analysis of 15 randomised trials of oral NMN found no significant effects on body weight, BMI, fasting glucose, HbA1c, lipid profiles or systolic blood pressure. The molecule goes up. Most of what people buy it for does not follow.