Coenzyme Q10 (CoQ10) is a substance similar to a vitamin. It is found in every cell of the body. Your body makes CoQ10, and your cells use it to produce the energy your body needs for cell growth and maintenance. It also functions as an antioxidant, which protects the body from damage caused by harmful molecules. Coenzymes help enzymes work to digest food and perform other body processes, and they help protect the heart and skeletal muscles.