Riboflavin, or vitamin B2, regulates red blood cell growth and helps maintain a strong immune system by protecting the body from free-radical damage. Riboflavin also promotes healthy hair, skin, nails, and vision.
Without riboflavin, the other B vitamins, especially niacin (vitamin B3) and pyridoxine (vitamin B6), cannot do their job, and a host of chemical processes necessary to keep the body alive would come to a grinding halt.
You also need riboflavin to produce flavin mononucleotide and flavin adenine dinucleotide, two enzymes that help the body convert fats, carbohydrates, and proteins into energy. Without enough riboflavin, these two enzymes are unable to work together to ensure your cells can both reproduce correctly and supply the body with the fuel it needs stay alive.