Increased protein intake on controlled oxalate diets does not increase urinary oxalate excretion |
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Authors: | John Knight Linda H Easter Rebecca Neiberg Dean G Assimos Ross P Holmes |
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Institution: | (1) Department of Urology, Wake Forest University School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157, USA;(2) GCRC Bionutrition Unit, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA;(3) Department of Public Health Sciences, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA |
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Abstract: | 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. |
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Keywords: | Dietary protein Oxalate excretion Oxalate synthesis Glycolate Hydroxyproline |
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