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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.

Large quantities of ascorbic acid or erythorbic acid were administered to Swiss mice over a period of seven months. Urinary ascorbic acid and erythorbic acid were determined two weeks before termination of the experiment. At the end of the experiment, ascorbic acid and erythorbic acid contents in plasma, liver and brain tissues were measured. In the ascorbic acid-treated mice, there was a marked elevation in plasma and urine ascorbate levels, and there was a 38% increase of ascorbate level in the liver but there was no substantial increase in ascorbate levels in the four brain regions studied, namely the cerebrum, cerebellum, medulla and brain stem, upon large intake of ascorbic acid. In the erythorbic acid-treated mice, erythorbic acid is well absorbed by the gastrointestinal tract, enters the blood stream, and is rapidly excreted in the urine. The results show that erythorbic acid is able to replace 45% of ascorbic acid in the liver and 28-39% of ascorbic acid in the brain tissues. Although erythorbic acid appears in the blood at significantly high level, it does not lower blood ascorbate levels.