I like others was skeptical, but I listen to 99% of what coach Greg says. He promotes this stuff harder than last time in every video, more than any other supplement he takes or sells. With reason… this stuff works. I took it straight for 6 months, decided to cycle off to see what would happen, I am 45 years old, I am extremely active, nothing has changed except both taking the stuff… results… I need to go back on, I saw a substantial drop in my cardio routine. It’s not placebo, I strive to push hard without taking any supplements except creatine. Bottom line, NMN works, been without it for 2 months, going back on and not stopping.