Does high-oxalate food cause oxalate stones? – Review of dietary factors affecting the risk of oxalate urolithiasis.

Abstract

Introduction: Oxalate urolithiasis is the most common type of kidney stones, accounting for 70-80% of cases. Under certain conditions, such as: high oxalic acid concentration, high calcium levels, damaged tubular epithelium, urinary tract infections and oxidative stress, calcium oxalates may precipitate and initiate the formation of kidney stones. The aim of the study is to review the available literature on the possibility of dietary factors to modify the risk of oxalate urolithiasis. State of knowledge: Oxalates are found in most plant foods. Sorrel, rhubarb, chard, soy and cocoa are examples of high-oxalate foods. However, only 10% of oxalic acid which circulates in the bloodstream come directly from food, and 90% is a product of hepatic metabolism, and its main precursor is hydroxyproline, the amino acid typical for animal proteins: collagen and elastin. The increase in the risk of oxalate urolithiasis is also affected by too low fluid intake, excessive vitamin supplementation, as well as high levels of simple sugars and sodium consumption. Although plant products are a source of oxalic acid, they also contain antioxidants, especially polyphenols and vitamins, as well as citric acid and potassium, which reduce the risk of calcium oxalate formation. Conclusions: Changing nutritional habits into the diet rich in vegetables, fruits and herbs, parallel with reducing the consumption of animal proteins, as the main source of hydroxyproline, should form the basis for prophylaxis of oxalate kidney stones.

Keywords

• oxalic acid
• oxalate urolithiasis
• vegetable diet
• glyoxylic acid
• hydroxyproline