Inositol hexakisphosphate in urine: the relationship between oral intake and urinary excretion

Objective  To study the relationship between the oral intake of inositol hexakisphosphate ( Ins P 6 , phytic acid, an inhibitor of urinary crystallization) and its urinary excretion, to establish their possible mutual influence. Materials and methods  Two groups of male Wistar rats (six animals each) received either; tap water and normal rat food pellets (controls); or a liquid diet in which Ins P 6 was absent and which then received gradually increasing amounts of Ins P 6 . The urinary levels of Ins P 6 were then assessed regularly in both groups. Results  When Ins P 6 was absent from the diet, urinary excretion declined to undetectable levels after 22 days. The addition of increasing amounts of Ins P 6 to the liquid diet caused an increase in its urinary excretion after about 10 days. Adding Ins P 6 in amounts > 425 mg/L caused no further increases in urinary excretion. Adding inositol (with no Ins P 6 ) to the liquid diet caused only a slight increase in the urinary excretion of Ins P 6 . Conclusion  These results showed that Ins P 6 urinary levels were related to its oral intake; consequently, a low consumption of Ins P 6 would cause a urinary deficit of this crystallization inhibitor and thus an increase in the risk of developing urinary calcium stones. Although urinary excretion was dose‐dependent, there was an ingested amount (20.9 mg/kg) above which there was no increase in the amount excreted. This intake is easily obtained by consuming a normal diet (rich in Ins P 6 ) indicating that to maintain appropriate urinary levels of Ins P 6 , the consumption of Ins P 6 supplements is only necessary when the diet is particularly poor in Ins P 6 .