Sufficient vitamin D in the diet is essential for calcium absorption.
Parathormone, a hormone produced by the parathyroid gland, controls the levels of calcium in the blood.
Oestrogen, a hormone in premenopausal women, promotes calcium absorption.
Phosphorus, which combines with calcium to form calcium phosphate, must be present in the correct proportions.
An acid enviroment aids calcium absorption. This can be enhanced by combining vitamin C with calcium foods.
Protein is necessary for calcium absorption - the calcium is absorbed into the blood stream by becoming bound to protein.