NAD (or nicotinamide adenine dinucleotide) is a vital resource found in all living cells. We use it every day. After over 100 years of studying this molecule, researchers are publishing more articles about NAD than ever before. Now we know NAD isn’t a constant resource. Things like overeating, staying in the sun too long, or drinking alcohol can stress our system and cause NAD to decline. Some scientists even think this NAD decline plays a major role in how we age.