The body needs 13 vitamins: a-e, c-k, and b-b12. Minerals such as calcium, phosphorus, potassium, sodium, chloride, magnesium, iron, zinc, iodine, chromium, copper, fluoride, molybdenum, manganese, and selenium are present in meals. Some vitamins are best taken on an empty stomach, others after a meal. Experts believe most vitamin and mineral supplements aren't worth the effort to take. Magnesium is required for many bodily processes, including muscle and neuron function, as well as energy production.