Calcium and Phosphorus

Calcium and phosphorus, two minerals found in abundance in the body, are involved in several vital physiological processes. Maintenance of homeostasis for both elements is fundamental to disease prevention in the aging adult with regards to musculo-skeletal health and other disorders. Calcium and phosphorus absorption occur via transcellular and paracellular pathways. Their regulation is maintained by interactions of three hormones: parathormone, vitamin D, and calcitonin. Parathormone and vitamin D enhance calcium and phosphorus absorption in the intestine; at the renal level parathormone helps absorb calcium but promotes phosphorus excretion, while vitamin D enhances both calcium and phosphorus renal absorption. The active form of calcium is the free or ionized calcium, but seldom measured. Over the years, in the USA, the intake of calcium has increased, largely as supplements. The most common cause of hypercalcemia is primary hyperparathyroidism (PHPT), followed by cancer; PHPT may be from hyperplasia of the glands, adenoma or a carcinoma. Hypocalcemia may result from removal of the parathyroid glands or from malabsorption of calcium (and vitamin D) in the gastrointestinal tract, due to several causes. Lactose intolerance is a common reason for inadequate calcium intake; affected individuals must use other means to meet requirements for calcium. The intake of phosphorus has also increased, with the sources largely from diet. Outcome studies have not demonstrated a consistent benefit from calcium intake as supplements or diet for the prevention of fractures and other health outcomes, and the prevention of gastrointestinal cancer. Deficiencies in both calcium and phosphorus are associated with several adverse consequences in older people, particularly with regard to bone health and in the case of phosphorus to several organ systems. The requirements of calcium are perhaps best met by dietary sources, with supplements in limited amount for those who do not meet requirements from the diet alone. A balanced diet is the best means to provide the RDA for both calcium and phosphorus.