NAD+ (nicotinamide adenine dinucleotide)

What it is

Cells use NAD+ and its reduced form, NADH, to carry electrons in metabolism, and signalling enzymes consume NAD+. Levels fall with age and stress, but much about NAD+ biology remains poorly understood.

What it is studied for

Research asks whether raising NAD+ improves aging and metabolic health. Most human trials gave oral precursors such as nicotinamide riboside (NR) or NMN. A pilot at a clinic offering NAD+ infusions gave 8 men a 6-hour IV infusion of NAD+, with 3 men given saline, to track blood and urine levels.

What the evidence says

Limited human data; mostly precursor studies

In that pilot, blood NAD+ did not rise during the first 2 hours, and no adverse events were seen. Oral precursors raise NAD-related markers, but effects on function and metabolism have been mixed and often null. Claims that NAD+ products boost energy or slow aging lack human outcome evidence.

How it was studied

Human studies mostly used oral precursors, and NAD+ itself was given by IV infusion in a small pilot. Intranasal NAD+ was tested in a rat stroke model. Dissolving strips and nasal sprays were not the forms studied in people.