Vitamin B3 obtained from the diet is converted in our body into its active form, NAD biomolecules. A biomolecule is a molecule that is essential for the structure and function of living organisms. NADs (nicotinamide adenine dinucleotides) are coenzymes that are essential for metabolism. NADs are found in every living cell. There are four different types of NAD: NAD+, NADH, NADP+, and NADPH.