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UROSCAN
Year : 2006  |  Volume : 22  |  Issue : 4  |  Page : 386-387
 

Dietary modifications for preventing recurrent stones


Department of Urology, All India Institute of Medical Sciences, New Delhi, India

Correspondence Address:
Rajiv Yadav
Department of Urology, All India Institute of Medical Sciences, New Delhi
India
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Source of Support: None, Conflict of Interest: None


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How to cite this article:
Yadav R, Kumar R. Dietary modifications for preventing recurrent stones. Indian J Urol 2006;22:386-7

How to cite this URL:
Yadav R, Kumar R. Dietary modifications for preventing recurrent stones. Indian J Urol [serial online] 2006 [cited 2019 Jun 24];22:386-7. Available from: http://www.indianjurol.com/text.asp?2006/22/4/386/29139

Borghi L, Schianchi T, Meschi T, Guerra A, Allegri F, Maggiore U, et al. Comparison of two diets for the prevention of recurrent stones in idiopathic hypercalciuria. N Engl J Med 2002;346:77-84.



   Summary Top


This prospective randomized study was performed to evaluate the role of a calcium restricted diet in preventing stone recurrence in patients with urolithiasis and hypercalcuria. One hundred and twenty men with recurrent urolithiasis and idiopathic hypercalciuria (urinary calcium excretion, > 300mg/day [7.5 mmol/day]) on unrestricted diet, were randomly assigned one of the two dietary regimens and followed for five years. Inclusion criteria included the absence of predisposing conditions for stone disease and no current treatment for the prevention of recurrent stones except for the advice to increase water intake. One group of 60 men was placed on a low-calcium diet (10 mmol/day) and the second group of 60 men consumed a diet with normal to high calcium (30 mmol/day), low proteins (52 g/day), particularly animal proteins and low salt (50 mmol of sodium chloride/day). Both groups were advised to avoid oxalate-rich foods. Twenty-four-hour urine specimens were obtained at baseline (before randomization), one week after randomization and at yearly intervals during the five years of the study. The primary outcome measure was the time to the first recurrence of a symptomatic renal stone or the presence of a radiographically identified stone. If there were no recurrences, patients were followed until the fifth annual visit (Month 60). Secondary outcome measures included changes in calcium and oxalate excretion, the calcium oxalate product and the relative calcium oxalate saturation.

Twenty-three out of the 60 men on the low-calcium diet and 12/ 60 on the normal-calcium, low-protein, low-salt diet had recurrences. The relative risk (RR) of a recurrence among the men in the normal calcium, low-protein, low-salt group, as compared with the men in the low-calcium group, was 0.49. Significant difference in stone recurrence was observed only late in the follow-up period signifying that early recurrence may be observed in higher risk patients regardless of the dietary modification. The 24h urinary volume was similar in the two groups. Patients with low-calcium diet showed no change in urinary excretion of sodium, urea nitrogen and sulfate. All three parameters decreased with the normal-calcium, low-protein and low-salt diet reflecting dietary compliance. Calcium excretion decreased with both diets (by approximately 170 mg /day [4.2 mmol / day]). The main difference between the two diets was oxalate excretion, which increased with the low-calcium diet but decreased with the normal-calcium, low-protein, low-salt diet. There was no difference in dietary compliance between the men with or without recurrence, irrespective of diet.


   Comment Top


The need for dietary modification is a valid concern in the minds of both the patients and the treating physician following a stone episode. High urinary calcium is a risk factor for recurrent stone disease.[1] This has traditionally been extrapolated into dietary calcium restriction for preventing recurrence. However, dietary calcium restriction has been questioned due to potential risk of hyperoxaluria resulting from the low level of calcium available to form a complex with oxalate in the intestinal lumen. Calcium oxalate saturation of urine increases rapidly with small increases in the oxalate concentration.[2] This study compares the effect of dietary calcium on the incidence of stone recurrence in patients with calcium oxalate stone and proved hypercalciuria. Apart from modification of calcium content, patients were instructed not to indulge in oxalate-rich food in both the dietary regimens. The decrease in calcium oxalate product and the relative calcium oxalate saturation was observed with both calcium-restricted and normal-calcium diets. The reduction was greater with the normal-calcium, low-protein and low-salt diet. The main difference between the two diets was oxalate excretion, which increased with the low-calcium diet but decreased with the normal-calcium, low-protein, low-salt diet.

This randomized study provides evidence supporting the efficacy of normal amount of calcium but with reduced amounts of animal protein and salt in comparison to the traditional low-calcium diet in the prevention of stone recurrence. A low-calcium diet has additional detrimental effects in the form of osteoporosis and the simplification of dietary advice to good fluid intake, low salt and low proteins may also increase the compliance. However, the beneficial effect may be observed after a prolonged period, especially in patients with higher risk of recurrence.

 
   References Top

1.Ettinger B. Recurrence of nephrolithiasis. A six-year prospective study. Am J Med 1979;67:245-8.  Back to cited text no. 1    
2.Borsatti A. Calcium oxalate nephrolithiasis: Defective oxalate transport. Kidney Int 1991;39:1283-98.  Back to cited text no. 2  [PUBMED]  




 

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