Influence of dietary chloride on fluoride bioavailability in the rat.

A factorial experiment was conducted with weanling rats fed a purified diet to determine the influence of dietary chloride (0.02, 0.10 and 0.50%) as sodium chloride on fluoride bioavailability (2 or 10 ppm as sodium fluoride). After 6 wk, rats fed the lowest chloride-containing diets had significant reductions of plasma chloride, urinary chloride excretion and growth rate compared to other chloride groups. Depressed growth occurred in rats fed chloride-deficient diets despite the fact that food intake was similar for all treatments. Fluoride retention was greatest in chloride-deficient rats, which was reflected in enhanced skeletal uptake of fluoride. Fluoride absorption was not inhibited by high chloride intake. We therefore conclude that emphasis on the effect of chloride on fluoride bioavailability should be directed towards an enhancement of fluoride retention by low salt (sodium chloride) diets rather than in terms of a possible negative effect of a high salt diet on fluoride absorption.