Urinary oxalate excretion after large intakes of ascorbic acid in man

Abstract

The influence of high dose intake of ascorbic acid on the urinary excretion of oxalate was investigated in five healthy male volunteers. Oxalate was measured by a newly developed specific method using isotachophoresis. With intakes of 10 g ascorbic acid (5 X 2 g daily for 5 days; four subjects) mean urinary oxalate excretion was enhanced from about 50 mg to 87 mg (range 60 to 126 mg) per day. At least 25% of the ascorbic acid was absorbed and excreted with the urine. On discontinuing ascorbic acid administration, oxalate excretion returned to baseline values within 24 h. The time-course of oxalate excretion revealed that following the 3rd dose of 2 g ascorbic acid a plateau in urinary oxalate excretion was reached (0.6 microgram ml-1 min-1) which was not exceeded despite additional 2-g doses of ascorbic acid. On termination of ascorbic acid administration the oxalate excretion rate remained at this level for a further 6 h and then decreased to prestudy rates. No effect of high-dose ascorbic acid ingestion was found on the daily urinary excretion of creatinine, uric acid, and inorganic phosphate. Calcium excretion was slightly reduced. In comparison to the large amounts of ascorbic acid ingested, the increase in urinary oxalate excretion as measured by isotachophoresis in these healthy male volunteers was very low, and is thus similar to the change in urinary content of oxalate which results from consuming normal diets.

Nutritional Contribution of Some Senegalese Forest Fruits Running across Soudano-Sahelian Zone

“…From the later reference, we are leading researches on the antioxidant activities which can be improved by crudes fibers, total polyphenol content, total flavonoids in these forest fruits. However, the moderated consumption of S. latifolius has been suggested because, an exceed consumption of vitamin C engenders some gust intestine troubles [32], some oxalate crystal formation in the urinary system [33] and indeed red globulins hemophiliac [34].…”

Is it safe to prescribe ascorbic acid for urinary acidification in stone-forming patients with alkaline urine?

“…However, they used daily doses of 10 g AA whereas in the present study 2000 mg was the maximum dosage (Table 3). [14] In the current study, one patient had his AA supplementation discontinued due to de novo hyperoxaluria and another had his dose reduced for the same reason. However, there was no significant increase in mean 24-hour urinary oxalate excretion.…”

“…This is similar to what Takigushi et al [15] found. Finally, Schmidt et al [14] found that at least 25% of AA is excreted in the urine and most AA is excreted in the urine as reduced AA. Therefore, 24-hour urine collections could be used to monitor the development of hyperoxaluria in patients receiving AA supplementation.…”

Effect of ascorbic acid on calcium elimination in humans.

“…Human studies show that long-term large intake of ascorbic acid did not affect urinary calcium excretion (14)(15)(16)(17)(18). The addition of ascorbic acid to the diet increased calcium absorption in women (19) and in children (20).…”

“…Animal experiments have shown that ascorbic acid administration caused a mobilization of calcium from cultured embryonic chick tibias (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29) and an increase in urinary calcium excretion from chicks (30) during the initial time of treatment. After 24 hours this effect was lost and eventually normal levels were attained.…”