Nicotinamide adenine dinucleotide (NAD) is a vitally important substance that is found in all cells of the body. Elevated levels of NAD are linked to health and well-being. The key objective of this pilot research study is to dose human volunteers with a heavy (non-radioactive) isotope derivative of nicotinamide to detect NAD synthesis in human skeletal muscle Our ultimate goal is to examine the impact of lifestyle choices, aging, nutraceuticals, and drugs on the rate of NAD synthesis in human subjects