Nicotinamide Mononucleotide (NMN) is a molecule derived from ribose, a simple sugar found in foods like mushrooms, beef, poultry, dairy and eggs, and nicotinamide, a form of Vitamin B3 occurring naturally in meat, and green vegetables. Inside the body, enzymes convert NMN to Nicotinamide adenine dinucleotide (NADH), which scientists believe plays a central role in activating cellular repair genes that promote longevity.