Magnesium-fluoride interrelationships in man II. Effect of magnesium on fluoride metabolism.

The effect of magnesium on the fluoride balance was investigated in man by determining metabolic balances of fluoride and magnesium in control studies and during magnesium supplementation. The magnesium intake averaged 264 mg/day in the control studies and 825 in the experimental studies. The studies were carried out during four calcium intakes that ranged from 200 to 2,200 mg/day and during phosphorus intakes ranging from 800 to 2,000 mg/day. The studies were carried out during a fluoride intake of about 4 mg/day that was due to the dietary fluoride content and the intake of water and during a high fluoride intake of 25 mg/day that was due to the addition of sodium fluoride. During the high magnesium intake, both the urinary and fecal magnesium excretions increased and the magnesium balances became more positive. These changes were not associated with any significant changes of either the urinary or fecal fluoride excretions or of the fluoride balances during the different intakes of calcium phosphorus, or fluoride.