The effect of differing dietary calcium and phosphorus contents on mineral metabolism and bone histomorphometry in young vitamin D-replete baboons.

Young baboons were fed semisynthetic, vitamin D-containing diets differing in calcium and/or phosphorus content over a 16 month study period. Diets low in calcium alone or low in both calcium and phosphorus led to the development of radiologic rickets and histologic features of osteomalacia at both 8 and 16 months. The diet which was low in calcium but which had a normal phosphorus content was associated with histologic features of hyperparathyroidism at 16 months; such features did not develop in animals fed the low calcium, low phosphorus diet. Biochemically the low calcium, normal phosphorus diet was associated with a transient fall in serum calcium around 8 months, and a more persistent elevation in serum phosphorus and alkaline phosphatase values during the latter half of the study. These biochemical changes were not seen in the baboons on the low calcium, low phosphorus diet. These results confirm that histological changes can occur as a result of dietary calcium deprivation in vitamin D-replete animals.