Advances in nutrition (Bethesda, Md.)

The importance of nicotinamide adenine dinucleotide (NAD + ) in human physiology is well recognized. As the NAD + concentration in human skin, blood, liver, muscle, and brain are thought to decrease with age, finding ways to increase NAD + status could possibly influence the aging process and associated metabolic sequelae. Nicotinamide mononucleotide (NMN) is a precursor for NAD + biosynthesis, and in vitro/in vivo studies have demonstrated that NMN supplementation increases NAD + concentration and could mitigate aging-related disorders such as oxidative stress, DNA damage, neurodegeneration, and inflammatory responses. The promotion of NMN as an antiaging health supplement has gained popularity due to such findings; however, since most studies evaluating the effects of NMN have been conducted in cell or animal models, a concern remains regarding the safety and physiological effects of NMN supplementation in the human population. Nonetheless, a dozen human clinical trials with NMN supplementation are currently underway. This review summarizes the current progress of these trials and NMN/NAD + biology to clarify the potential effects of NMN supplementation and to shed light on future study directions.