Nitrogen is present in the proteins used to build up the muscle and collagen from which our bodies are constructed.
Calcium and phosphorus are essential to the structures of bones and teeth. Sodium and potassium are employed in the transmission, along the nerves, of electrical signals from the brain. Though we require only a few milligrams of iron, zinc and magnesium each day, our requirements are still large enough for our diets, sometimes, to be deficient in them.
At the lower end of the scale, a handful of elements are needed in such tiny amounts that we are never likely to be short of them. Indeed the opposite problem can occur. If we eat these to even slight excess, they become quite poisonous.