The Effect of Calcium and Phosphorus on Fluoride Absorption

¹ Baylor University College of Dentistry, Dallas, Texas, and Indiana University Medical Center, Indianapolis, Indiana

When weanling rats were given 2 mg. calcium at 15, 30, and 60 minutes following the administartion of 2 mg. fluoride, a significant (p=<0.01) reduction in fluoride retention resulted, when compared with animals receiving fluoride alone. The degree of reduction in fluoride absorption, however, was not time-dependent.

The effect of phosphate given 15 and 60 minutes after fluoride ingestion was a significant (p=<0.01) increase in fluoride retention. The influence of phosphate was less pronounced when given after the longer time interval, possibly because of the rapid absorption of fluoride which had taken place before phosphate administration. When calcium and phosphate were given concurrently with fluoride, a reduction in absorption was obtained amounting to nearly 16 per cent of the fluoride given. The effect of calcium plus phosphate 15 minutes after fluoride ingestion was significantly less, suggesting that most of the fluoride had been absorbed during that time and was not available for interaction with the added calcium and phosphate. Interference with absorption may be the principal means by which dietary calcium and phosphorus interfere with fluoride utilization.