Metabolic balances of 210 Po and 210 Pb were determined under strictly controlled dietary conditions in adult males. The intakes of the two nuclides were due to the dietary contents of these radioisotopes, inhalation from the atmosphere, and smoking of cigarettes. No additional radioisotope was given. The mean dietary intake of 210 Pb was 1.25 pCi/day and of 210 Po, 1.63 pCi/day. The major pathway of excretion of both nuclides is via the gastrointestinal tract and the urinary excretion is much lower. The total excretions of 210 Pb and 210 Po were greater than the dietary intake and the overall balances were -0.28 and -0.16 pCi/day for the two nuclides, respectively, during a low calcium intake. The 210 Pb balances did not change significantly when the calcium intake was increased 7- to 10-fold except for one patient in whom the balance became more negative. The 210 Po balance was more negative during calcium intakes of 800 and 2200 mg than during a low calcium intake of 200 mg/day. The urinary and fecal excretions of the two radionuclides were not affected by the intake of sodium fluoride, while the diuretic compound Hydrodiuril appeared to decrease the fecal 210 Pb excretion.
The dietary intake and the urinary and fecal excretion of naturally occurring 226 Ra and 226 Ra balances were determined in man under strictly controlled dietary conditions. These provided the basis for calculating the 226 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 urinary 226 Ra excretion averaged 0.016 pCi/day, during a calcium intake of 1300 mg or 2600 mg/day, given as calcium gluconate, the urinary 226 Ra excretion did not increase, while during supplementation of the diet with milk the urinary 226 Ra excretion increased. On all calcium intakes the urinary 226 Ra excretion averaged 3% of the total excretion except that it was 12% on milk intake. The major pathway of 226 Ra excretion was via the intestine and the 226 Ra balances were in equilibrium under all study conditions. There was no correlation between the urinary 226 Ra and the urinary calcium excretion.