NAD (nicotinamide adenine denucleotide) – NAD (or NAD+) is a coenzyme central to metabolism. It boosts memory, improves mental clarity, improves mood and concentration, boosts neurological function, reduce symptoms of depression, and facilitates DNA repair. By the time we’re in our forties, levels of NAD have fallen to half of what they were when we were young. They continue to decline as the years pass. We can raise NAD by fasting, taking saunas and cold showers, doing HIIT exercise, doing strength training, and/or by taking NAD boosters.