High animal protein intake is a risk factor for calcium oxalate stone disease. The effect of dietary protein on the urinary excretion of calcium, acid and citrate is well established. However, its effect on oxalate excretion is unclear, due in part to an inadequate control of dietary oxalate intake in previous studies. This relationship warrants clarification due to the proposed important role of the metabolism of amino acids in endogenous oxalate synthesis. In this study, 11 normal subjects consumed controlled oxalate diets containing 0.6, 1.2 and 1.8 g protein/kg body weight/day. The analysis of 24 h urine collections confirmed that as protein intake increased, urinary calcium and glycolate increased and urinary pH and citrate decreased. The increased glycolate excretion was due in part to an increased hydroxyproline, but not glycolate consumption. Total daily urinary oxalate excretion did not change. When indexed to creatinine there was a small but significant decrease in oxalate excretion. This is most likely due to hyperfiltration. These results indicate that as dietary protein intake increases, the catabolism of diet-derived amino acids is not associated with an increased endogenous oxalate synthesis in normal subjects.
Dietary protein Oxalate excretion Oxalate synthesis Glycolate Hydroxyproline
Giannini S, Nobile M, Sartori L et al (1999) Acute effects of moderate dietary protein restriction in patients with idiopathic hypercalciuria and calcium nephrolithiasis. Am J Clin Nutr 69:267–271PubMedGoogle Scholar
Butz M, Hoffmann H, Kohlbecker G (1980) Dietary influence on serum and urinary oxalate in healthy subjects and oxalate stone formers. Urol Int 35:309–315PubMedCrossRefGoogle Scholar
Conyers RA, Need AG, Bracken A et al (1985) The effect of short-term dietary changes on biochemical values in blood and urine and on some urinary risk factors for calcium oxalate stone formation in humans. Int J Vitam Nutr Res Suppl 28:135–152PubMedGoogle Scholar
Juillet B, Fouillet H, Bos C et al (2008) Increasing habitual protein intake results in reduced postprandial efficiency of peripheral, anabolic wheat protein nitrogen use in humans. Am J Clin Nutr 87:666–678PubMedGoogle Scholar
Tiselius HG (1991) Aspects on estimation of the risk of calcium oxalate crystallization in urine. Urol Int 47:255–259PubMedGoogle Scholar
Wagner EA, Falciglia GA, Amlal H et al (2007) Short-term exposure to a high-protein diet differentially affects glomerular filtration rate but not acid–base balance in older compared to younger adults. J Am Diet Assoc 107:1404–1408. doi:10.1016/j.jada.2007.05.003PubMedCrossRefGoogle Scholar