Nicotinamide riboside reached ageing muscle and changed nothing in it
Twelve older men took 1,000 mg a day for 21 days. NAD-related metabolites rose in their thigh muscle and gene expression shifted, but mitochondria did not change.
What the study found
It reaches ageing muscle without changing how that muscle works
Twelve older men took 1,000 mg of nicotinamide riboside a day for 21 days, then had thigh muscle biopsied. Products of nicotinamide adenine dinucleotide metabolism rose there, including those of clearing the compound, and gene expression shifted. Mitochondrial performance did not change.
The caveat · Muscle NAD itself not shown to rise
Twelve men over 21 days is a mechanistic study, not an efficacy trial. What rose was the NAD metabolome, the family of related compounds including clearance products; the paper does not report that muscle NAD itself rose in proportion. The gene-expression changes ran downward in the energy and mitochondrial pathways, the opposite direction to the one the rationale predicts. One author invented the licensed patents behind the product and holds stock in the company selling it.