Effect of large intake of ascorbic acid on urinary and plasma oxalic acid levels.

Blood samples form ten healthy subjects, who had been ingesting 3-10 g of ascorbic acid for at least two years, were collected. The ascorbic acid and oxalic acid levels in the plasma of these subjects were measured. The concentrations of oxalic acid in these plasma samples are within the range of plasma oxalate levels of human subjects who were not ingesting ascorbic acid supplements. Large quantities of ascorbic acid (10 g/day) were administered to healthy human subjects. Daily urinary samples of these subjects were collected before and during treatment. Urinary ascorbic acid and oxalic acid levels of these samples were measured. Among the six subjects tested, five experienced no significant change on urinary oxalate excretion. Urinary oxalate level of one subject was significantly elevated upon the large intake of ascorbic acid. But the increased daily excretion of oxylate in this subject is within the changes in urinary oxalate content from consuming normal diets.