RELATIONSHIP OF PROTEIN-INTAKE TO URINARY OXALATE AND GLYCOLATE EXCRETION

The relationship of protein intake to urinary oxalate and glycolate ex cretion was examined in a large cohort (N = 101) of normal individuals on self-selected diets and in 11 individuals on controlled protein di ets. On self-selected diets no correlation was detected between protei n intake and urinary oxalate or glycolate excretion. A moderate but si gnificant correlation (r = 0.45; P < 0.001) of oxalate with urea excre tion was observed in males but not females, suggesting that there may be a link between urea and oxalate synthesis in males. On controlled p rotein diets mean oxalate excretion in females on days 7 to 10 of a hi gh protein diet (1.8 g/kg body wt) was 20% higher than on a low protei n diet (0.6 g/kg body wt; P = 0.02), but there was no difference in ma les. Glycolate excretion was significantly higher (P < 0.001) on the h igh protein diet than on the low protein diet in both sexes. Only a we ak precursor-product relationship was observed between glycolate and o xalate. A gender effect was apparent on both self-selected and control diets with females excreting more oxalate and glycolate relative to c reatinine than males. A pronounced inter- and intra-individual variabi lity in the excretion of oxalate was observed, even on controlled diet s. This suggests that genetic factors and physiological changes such a s hormonal fluctuations may contribute more to the variability in oxal ate excretion than the dietary intake of protein.