Osteoporosis: calcium, fluoride, and aluminum interactions.

A gradual loss of bone occurs with age. There are indications in the literature that not only calcium but also fluoride may play an important role in maintaining the bone mass. In view of the high incidence of osteoporosis and its complications, and in view of the fact that fluoride is beneficial for the treatment of osteoporosis, studies have been carried out in this research unit to determine the retention and excretion of fluoride both during a normal dietary intake of fluoride and during fluoride supplementation. Another problem to be examined was to delineate whether certain substances interfere with the intestinal absorption of fluoride and of calcium. One such substance is aluminum contained in commonly used antacids. The use of small amounts of aluminum-containing antacids increased fecal fluoride significantly, thereby decreasing the intestinal absorption of fluoride. In addition, the small doses of aluminum-containing antacids also affected the metabolism of calcium and phosphorus, the primary effect being complexation of phosphorus in the intestine leading to phosphorus depletion. This change in phosphorus metabolism was associated with an increase of the urinary and fecal calcium excretion resulting in a negative calcium balance. The dual effect of aluminum, namely in causing calcium loss and inhibition of the intestinal absorption of fluoride, can result in adverse effects on bone which may contribute to bone loss.