The effect of oral administration of calcium and magnesium on intestinal oxalate absorption in humans

Abstract

Calcium oxalate (CaOx) urolithiasis is the most common urinary stone disease (70–75 % of all stones consist of CaOx in countries with western diet). Oxalate is the most lithogenic substance in CaOx crystallisation in urine. Oxalate is either synthesized within the body or absorbed from food. As oxalate is not metabolized in the human body, it appears unchanged in urine. Conventional analysis methods cannot distinguish between endogenous and exogenous oxalate. Our [¹³C₂]oxalate absorption test enabled measurement of intestinal oxalate absorption and quantification of the influence of Ca- and Mg-supplementation on it. The effects of the oral administration of these supplements were compared in order to obtain valid data for recommendations for CaOx urolithiasis patients. A 10mmol supplement of both ions decreased the oxalate absorption significantly, calcium being more than twice as effective.

Revised version of a paper presented at the 26^th Annual Meeting of the German Association for Stable Isotope Research (GASIR) October, 6 to 8, 2003, Cologne, Germany.

Keywords:

• Absorption test
• Carbon-13
• Ca-supplementation
• Magnesium-supplementation
• Oxalate absorption

Acknowledgements

Supported by Deutsche Forschungsgemeinschaft Grants Un 91/1-3. We thank M. Klöckner and B. Bär for skillful assistance.

Notes

Revised version of a paper presented at the 26^th Annual Meeting of the German Association for Stable Isotope Research (GASIR) October, 6 to 8, 2003, Cologne, Germany.