Dietary oxalate and calcium oxalate stones: A theoretical or real concern?

Abstract

Oxalate is the end product of several metabolic pathways in many life forms, including plants and humans. In humans and other animals, oxalate must be excreted because there is no biological need for oxalate. In humans, the ability to manage oxalate, which originates from both endogenous and exogenous sources, relies on control of its gastrointestinal absorption (in the case of exogenous oxalate), on the control of endogenous synthesis, and on renal oxalate handling. Because urinary oxalate excretion is a major cause of calcium oxalate urolithiasis, oxalate is of interest. Currently there are no pharmacologic agents designed to reduce oxalate biosynthesis, oxalate absorption, or renal oxalate excretion. While there are numerous nutrition-related strategies aimed at reducing high urine oxalate, there is debate about their effectiveness, largely due to lack of evidence in the biomedical literature. In this chapter, the chemistry of oxalate is elucidated. Current medical management practices and their respective rationales are outlined, specifically focusing on areas of controversy.