Intake and Excretion Patterns of Naturally Occurring Radium-226 in Humans

The dietary intake and the urinary and fecal excretion of naturally occurring²²⁶ Ra and²²⁶ Ra balances were determined in man under strictly controlled dietary conditions. These provided the basis for calculating the²²⁶ Ra balances. These balance studies were carried out during a low calcium intake, during the addition of different amounts of calcium given as calcium gluconate, and during the intake of milk.²²⁶ Ra balances were also determined during conditions which affect the metabolism of calcium: during intravenous infusions of stable strontium, during infusions of ACTH, and during total calorie starvation. During a low calcium intake of an average of 243 mg/day, the urinary²²⁶ Ra excretion averaged 0.016 pCi/day, during a calcium intake of 1300 mg or 2600 mg/day, given as calcium gluconate, the urinary²²⁶ Ra excretion did not increase, while during supplementation of the diet with milk the urinary²²⁶ Ra excretion increased. On all calcium intakes the urinary²²⁶ Ra excretion averaged 3% of the total excretion except that it was 12% on milk intake. The major pathway of²²⁶ Ra excretion was via the intestine and the²²⁶ Ra balances were in equilibrium under all study conditions. There was no correlation between the urinary²²⁶ Ra and the urinary calcium excretion.