In an 8-week week long, randomized, double-blind, placebo-controlled study involving 120 healthy adults between the age of 60 and 80-years-old, a 250mg daily dose of nicotinamide riboside and pterostilbene (a natural compound found in blueberries that activates sirtuin similar to resveratrol) increased participants' whole-blood NAD Levels by 40% compared to their baseline levels just after 4 weeks. Participants' whole-blood NAD levels increased by 90% when taking a double, dose which was 500mg.