ABSTRACT
For decades there has been a controversy about the relation of calcium deficiency to osteoporosis and the possibility of preventing bone loss by giving extra calcium16. In the background to this controversy, it is known that in postmenopausal women with oestrogen deficiency there is defective calcium absorption and negative calcium balance. Since there is also bone loss at the same time, it was reasonable to consider that the osteoporosis is due to the malabsorption of calcium and that increasing calcium intake should therefore reduce the rate of bone loss. Another possibility exists, however-namely, that the negative calcium balance is the result of the bone loss, in which case giving calcium would not be expected to have an effect on bone loss. Measurement of bone density by DXA has made it possible to show that additional calcium may increase peak bone mass and slow bone loss4,17; further, together with vitamin D in physiological amounts, it appears to reduce fracture rate18. Thus, studies on identical twins have shown that the rate of increase of BMD is greater in twins given additional calcium19, and similar results have been obtained in adolescent non-twin girls20. However, it is not clear how long this benefit is maintained.
