Calcium is one of the complementary nutrients that is essential for musculoskeletal strength, vascular contraction and vasodilatation, muscle function, nerve transmission, intracellular signaling, and hormonal secretion, digestion and blood clotting. A calcium deficiency can cause spasms of the hands and feet (tetany), muscle cramps, abdominal cramps, overly active reflexes, and so on. Chronic calcium deficiency contributes to poor mineralization of bones, soft bones (osteomalacia) and osteoporosis and, in children, rickets and impaired growth.
Excessive intake of calcium can result in harmful side effects. The most common side effects of calcium supplements include nephrolithiasis and gastrointestinal effects (e.g., constipation, dyspepsia, nausea, vomiting).