NAD+ Promotes Stem Cell Renewal and Regenerates Mitochondria. NAD+ has been shown to renew existing stem cells, repair broken DNA and extend lifespan. However NAD+ will not work, without your body having enough sirtuin proteins. After learning how to increase my sirtuin protein levels, I could then take Nicotinamide Riboside and NADH 20 mg, and have miraculous improvements in energy, mood and productivity, lasting 10 or more hours of the day.