THE EFFECTS OF ORAL ADMINISTRATION OF MAGNESIUM OXIDE ON RENAL CALCIUM EXCRETION IN CREW MEMBERS DURING A SUBMARINE PATROL by LCDR

Twenty-four urine specimens were collected from randomly selected members of the crew of the U.S. Navy Submarine NATHAN HALE, SSBN623, while at sea on a routine patrol mission. Specimens were collected three days after submergence, and again a few days before return to port. Twenty-one men received daily dosages of 310 mg of magnesium oxide orally, while nineteen served as controls. Urine specimens were examined microscopically, then measured for calcium, phosphorus, and routine factors. No urine specimen examined was found to contain bacteria or white blood cells, nor was there any alteration in the routine chemistries. Total urinary calcium excretion in the control group fell from a mean of 178 mg pre-patrol to 135 mg post-patrol, while the group ingesting magnesium oxide exhibited a sample mean of 162 mg calcium post-patrol, which is a significantly different mean value (p=0.05). Phosphorus excretion was not significantly variant. These data indicate that magnesium oxide does have an ionic effect on urinary chemical excretion and may explain the so-called "protective mechanism."