Riboflavin, also known as Vitamin B2, has many functions in common with the other members of the B complex family. These include support of the immune and nervous systems and formation of healthy red blood cells. Riboflavin provides essential factors for the production of cellular enzymes that turn proteins, fats, and carbohydrates into energy. It also participates in cell reproduction, and keeps skin, hair, nails, eyes, and mucous membranes healthy. Folic acid (vitamin B9) and pyridoxine (vitamin B6) are activated by riboflavin.
Recent research has found that riboflavin is involved in the regulation of circadian (daily) rhythms in humans and other mammals. Riboflavin helps to activate certain light-sensitive cells in the retina of the eye that synchronize the animal's daily biological rhythms with the solar light/darkness cycle. (This is because riboflavin allows you to bind copper to it's carrier protein. Bound copper activates the pineal gland which regulates the circadian sleep cycle.)