Vitamin & Mineral Guide Crucial Role of VitaminsVitamins are natural substances found in plants and animals and known as Essential nutrients for human beings. The body uses these substances to stay healthy and support its many functions.. There are 13 vitamins your body needs. They are vitamins A, C, D, E, K and the B vitamins. What Do They Do, and. Your body needs them to work properly, so you grow and develop just like you should. When it comes to vitamins, each one has a special role to play. Why? It’s a safe method of optimizing your dietary sources of nutrients.