Calcium is the most abundant mineral in the body. It is needed for strength and structure of teeth and bones, blood clotting, nerve function, muscle contraction and relaxation, enzyme regulation, and membrane permeability.

Most of the calcium in the human body is found in teeth and bones. This amount is continually in flux, with various amounts being deposited and resorbed. Later in life, more calcium is resorbed than is replaced, leading to bone loss and potentially to osteoporosis if calcium intake is inadequate (or has been inadequate in the past).

Good sources of calcium are broccoli, legumes, fortified orange juice, dairy products, and fish. Many dairy products are also fortified with vitamin D, which plays an important role in calcium absorption.