Safety assessment of nicotinamide riboside, a form of vitamin B₃

Nicotinamide riboside (NR) is a naturally occurring form of vitamin B₃ present in trace amounts in some foods. Like niacin, it has been shown to be a precursor in the biosynthesis of nicotinamide adenine dinucleotide (NAD+). The safety of Niagen™, a synthetic form of NR, was determined using a bacterial reverse mutagenesis assay (Ames), an in vitro chromosome aberration assay, an in vivo micronucleus assay, and acute, 14-day and 90-day rat toxicology studies. NR was not genotoxic. There was no mortality at an oral dose of 5000 mg/kg. Based on the results of a 14-day study, a 90-day study was performed comparing NR at 300, 1000, and 3000 mg/kg/day to an equimolar dose of nicotinamide at 1260 mg/kg/day as a positive control. Results from the study show that NR had a similar toxicity profile to nicotinamide at the highest dose tested. Target organs of toxicity were liver, kidney, ovaries, and testes. The lowest observed adverse effect level for NR was 1000 mg/kg/day, and the no observed adverse effect level was 300 mg/kg/day.