Abstract
Twenty-nine metabolic balance studies have been performed on seventeen patients with spinal and mixed osteoporosis. The patients went into strongly sustained positive balance when given calcium supplements. The mean calcium requirement of these patients with osteoporosis was significantly higher than that of normal subjects. This was largely due to their inability to vary their urine calcium with variations in their dietary intake. The results are compatible with the concept that osteoporosis is due to prolonged negative calcium balance occurring in subjects with a higher than normal calcium requirement or unable to adapt to an inadequate intake.