Stiff old arteries contribute to cardiovascular disease in the elderly, which is a leading cause of death. De Picciotto et al. report that age-related deterioration in the flexibility of the carotid artery in mice could be reversed when animals received dietary supplementation of nicotinamide mononucleotide (NMN). NMN is an intermediate in the synthesis of NAD+ (the reduced form of nicontinamide adenine dinucleotide), which improved metabolic function and stress responses in older animals. Treatment of mice with NMN for 8 weeks improved measures of elasticity in large arteries. NMN may act, at least in part, by activating sirtuin 1, an NAD+-dependent protein deacetylase. Dietary supplementation of NMN may thus provide a therapeutic strategy to reverse arterial dysfunction in the elderly.