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Dietary oxalate and its intestinal absorption
R P Holmes1, H O Goodman, D G Assimos
1Department of Urology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem NC, 27157, USA. rholmes@isnet.is.wfu.edu
Scanning Microscopy
|January 1, 1995
Summary
Dietary oxalate significantly impacts urinary oxalate levels, contrary to previous beliefs. Reducing oxalate intake and increasing calcium, magnesium, and fiber can modify absorption, aiding in managing stone disease risk.
Area of Science:
- Nephrology
- Nutritional Science
- Biochemistry
Background:
- Current understanding suggests dietary oxalate contributes minimally (<20%) to urinary oxalate.
- Recent studies indicate dietary oxalate may be a significant risk factor for stone disease.
- Previous research faced limitations due to inaccurate food oxalate data and methods for assessing intestinal absorption.
Purpose of the Study:
- To re-evaluate the contribution of dietary oxalate to urinary oxalate excretion.
- To review factors influencing oxalate absorption.
- To examine new methods for measuring food oxalate and intestinal oxalate absorption.
Main Methods:
- Utilized capillary electrophoresis for accurate food oxalate analysis.
- Employed an oxalate-free formula diet for two individuals over 7 days.
- Restored oxalate to the formula diet to assess absorption modification.
Main Results:
- Urinary oxalate excretion decreased by an average of 67% (18.6 mg/24 hours) on the oxalate-free diet.
- Fecal oxalate was undetectable by day 6, suggesting minimal absorption on the formula diet.
- Restoring oxalate to the diet increased urinary oxalate excretion, validating the protocol.
Conclusions:
- Intestinal absorption of dietary oxalate significantly contributes to urinary oxalate levels.
- Dietary oxalate absorption can be modified by reducing intake or increasing calcium, magnesium, and fiber.
- The experimental protocol is suitable for studying oxalate absorption and its modulators.