Dietary style and acid load in an Italian population of calcium kidney stone formers

- A specific algorithm measures the acid load of diet as potential renal acid load (PRAL).
- Calcium stone formers showed a lower fiber and potassium intake and a higher PRAL.
- Dietary acid load was associated with a decrease in citrate excretion.
- An imbalance between animal and vegetal protein intake may increase PRAL.
- An imbalance between animal and vegetal protein intake may predispose to stones.

Background and aimsAnimal protein intake may cause an acid load that predisposes individuals to stones by influencing calcium and citrate excretion. These associations were not confirmed in recent studies. Therefore the present study was aimed to compare acid load of diet in stone formers and controls.Methods and resultsParticipants to the study were 157 consecutive calcium stone formers and 144 controls. Diet was analyzed in these subjects using a software that evaluated nutrient intake from a three-day food intake diary. This software also estimated the potential renal acid load (PRAL, mEq/day). Twenty-four-hour urine excretion of ions and citrate was measured in stone formers.Stone former diet had lower intake of glucose, fructose, potassium and fiber and higher PRAL in comparison with controls. The multinomial logistic regression analysis showed that stone risk decreased in association with the middle and the highest tertiles of fiber intake and increased in association with the highest tertile of PRAL. The linear multiple regression analysis showed that calcium excretion was associated with the sodium excretion and that citrate excretion was associated with the PRAL and animal protein intake in stone formers.ConclusionOur findings suggest that stone formers may undergo a greater dietary acid load sustained by a low vegetable intake and base provision. Dietary acid load does not appear as the main determinant of calcium excretion, but may promote stone risk by decreasing citrate excretion. Sodium intake may predispose to stones by stimulating calcium excretion.