Effects of caffeine on fluoride, calcium and phosphorus metabolism and calcified tissues in the rat.

This 6-week study was designed to determine the effects of graded doses of caffeine intake (3, 25 or 100 mg/kg per day) on the metabolic balance and tissue concentrations of fluoride, calcium and phosphorus in Sprague-Dawley rats. Caffeine intake did not affect the absorption, urinary excretion or balance of fluoride, the plasma, bone or enamel concentrations of fluoride, nor the occurrence of incisor enamel fluorosis. Neither did it affect the metabolism of calcium or phosphorus except that the urinary excretion of calcium was increased. This effect, however, was not sufficient to influence significantly calcium balance. The ash content of the femur epiphysis and bone mineral content of the tibia were significantly reduced only in the group exposed to the highest dose of caffeine. These effects on bone were not significantly related to the balance of calcium or phosphorus. It was concluded that caffeine, even at an extremely high level of intake, has no detectable effect on the balance or tissue concentrations of fluoride, calcium or phosphorus in the rat.