NAD+

NAD+ is a coenzyme rather than a peptide, and its role in cellular energy metabolism is fundamental and long established. Interest in it here follows from observations that tissue levels decline with age and from its role as a substrate for sirtuin and PARP enzymes.

Most of the credible research concerns precursors — nicotinamide riboside and nicotinamide mononucleotide — which raise NAD+ levels when taken orally and have been studied in human trials. Direct intravenous NAD+ infusion is a different intervention with a much thinner evidence base, and results from precursor trials should not be read as supporting it.

Cellular energy metabolism, sirtuin activity and age-related decline in NAD+ levels. Human trials exist mainly for oral precursors rather than for direct infusion.

Oral precursors are reported as well tolerated in the published trials. Intravenous infusion is commonly associated with flushing, chest tightness and nausea during administration, and rate-related discomfort is frequently described.

Available as oral precursor capsules, as sterile solution for intravenous infusion, and in subcutaneous preparations. These are not equivalent to one another.