Increase in urinary calcium and oxalate after fructose infusion.

We have previously shown that an oral glucose load increased both calciuria and oxaluria while the ingestion of fructose induced a rise in calciuria and a decrease in oxaluria. This latter effect remains unclear and might be linked to the reduced intestinal oxalate absorption subsequent to digestive intolerance in some subjects. Such a hypothesis could be enlightened by the study of a parenteral fructose load. Therefore in 7 healthy subjects, we compared the effects of fructose infusion (F) (15 min iv infusion at 0.185 mmol/kg BW/min) to a control glucose infusion (G) on urinary calcium and oxalate. In this study, glycemia and insulinemia increased less after (F) than after (G) (respectively + 21% vs + 216%, p < 0.001 and + 230% vs + 402%, p < 0.05) and phosphatemia decreased less after (F) than after (G) (-7% vs -14%, p < 0.05). Urinary calcium and oxalate increased only after (F) (respectively + 64%, p < 0.01 and + 60%, p < 0.05). Urinary uric acid, another urolithiasis factor, increased after both (F) and (G) (respectively + 45%; p < 0.01 and + 42%; p < 0.01) but uricemia increased only after (F) (+ 25%; p < 0.01). Our results suggest an additional reason to avoid the use of fructose in parenteral nutrition, particularly in individuals with a known history of either calcium oxalate or urate urolithiasis.