What exactly are vitamins?

Vitamins are substances that our bodies require to function correctly. We have to get them from our diets because we can’t create most of them. There are 13 vitamins in all, and they are classified as micronutrients since humans only require little amounts of them every day, often milligrams (mg) or micrograms (mcg or g). 1 Vitamin D is an exception, as it is produced by the action of sunshine on our skin. Vitamin B3, commonly known as niacin, can be made from an amino acid called tryptophan, but we still need to receive it from foods like nuts, seeds, tofu, cheese, meat, fish, oats, beans, lentils, and eggs.