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


RESULTS
Participants 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.


CONCLUSIONS
Our 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.
Nephrology and Dialysis Unit, Postgraduate School of Nephrology, Vita Salute University, San Raffaele Scientific Institute, 20132 Milan, Italy. Electronic address: vezzoli.giuseppe@hsr.it.
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Vezzoli
Department of Health Sciences, Università degli Studi di Milano, San Paolo Hospital, 20142 Milan, Italy.
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Dogliotti
Department of Health Sciences, Università degli Studi di Milano, San Paolo Hospital, 20142 Milan, Italy; Sidra Medical and Research Center, Doha, Qatar.
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Terranegra
Nephrology and Dialysis Unit, Postgraduate School of Nephrology, Vita Salute University, San Raffaele Scientific Institute, 20132 Milan, Italy.
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Arcidiacono
Nephrology and Dialysis Unit, Postgraduate School of Nephrology, Vita Salute University, San Raffaele Scientific Institute, 20132 Milan, Italy.
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Macrina
Department of Health Sciences, Università degli Studi di Milano, San Paolo Hospital, 20142 Milan, Italy.
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Tavecchia
Department of Health Sciences, Università degli Studi di Milano, San Paolo Hospital, 20142 Milan, Italy.
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Pivari
Nephrology and Dialysis Unit, Postgraduate School of Nephrology, Vita Salute University, San Raffaele Scientific Institute, 20132 Milan, Italy; Department of Health Sciences, Università degli Studi di Milano, San Paolo Hospital, 20142 Milan, Italy.
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Mingione
Department of Health Sciences, Università degli Studi di Milano, San Paolo Hospital, 20142 Milan, Italy.
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Brasacchio
Department of Clinical Sciences, University of Parma, Parma, Italy.
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Nouvenne
Department of Clinical Sciences, University of Parma, Parma, Italy.
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Meschi
Department of Health Sciences, Università degli Studi di Milano, San Paolo Hospital, 20142 Milan, Italy.
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Cusi
Nephrology and Dialysis Unit, Postgraduate School of Nephrology, Vita Salute University, San Raffaele Scientific Institute, 20132 Milan, Italy.
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Spotti
Urology, Department of Health Sciences, Università degli Studi di Milano, San Paolo Hospital, 20142 Milan, Italy.
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Montanari
Department of Health Sciences, Università degli Studi di Milano, San Paolo Hospital, 20142 Milan, Italy.
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Soldati
D000328:Adult; D015415:Biomarkers / Q000652:urine; D002118:Calcium / Q000652:urine*; D016022:Case-Control Studies; D002951:Citrates / Q000652:urine; D004043:Dietary Fiber; D004044:Dietary Proteins / Q000009:adverse effects*; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007558:Italy; D007669:Kidney Calculi / Q000175:diagnosis / Q000209:etiology* / Q000652:urine; D016014:Linear Models; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D015596:Nutrition Assessment; D009752:Nutritional Status; D016017:Odds Ratio; D065840:Protective Factors; D065667:Renal Elimination; D012307:Risk Factors; D012964:Sodium / Q000652:urine; D012982:Sodium, Dietary / Q000009:adverse effects; D016482:Urinalysis; D014675:Vegetables
D015415:Biomarkers; D002951:Citrates; D004043:Dietary Fiber; D004044:Dietary Proteins; D012982:Sodium, Dietary; D012964:Sodium; D002118:Calcium
Acid load; Calcium excretion; Citrate excretion; Kidney stones; Vegetable intake