Interrelations of calcium, fluorine and vitamin D in bone metabolism

The interrelationships between dietary calcium, fluorine and vitamin D were studied in young rats. 2. Rats maintained on a low-Ca diet gained less weight and had less ash in their bones. Their femurs incorporated more radioactive Ca than those of rats kept on a control diet. Supplementation of the diet with F slightly decreased growth and the content of bone ash without any effect on the content of Ca and phosphorus in the bone ash. The F supplement decreased uptake of radioactive Ca by bone. Addition of vitamin D to a low-Ca diet improved growth and, when added alone, increased uptake of radioactive Ca by bone without affecting the content in femurs of ash, Ca or P. Addition of F to a low-Ca diet supplemented with vitamin D diminished the uptake of radioactive Ca. 3. Decrease of bone ash in rats fed the low-Ca diet was accompanied by an increase in bone nitrogen. The bones of the unsupplemented rats contained less citric acid per unit of dry, fat-free mass. Addition of F decreased citric acid, whereas addition of vitamin D increased it. 4. The results are discussed and it is concluded that vitamin D added to a low-Ca diet does not exert a calcifying effect on bone, but rather increases Ca turnover. F, on the other hand, reduces the exchangeability of bone mineral.