A case-control study of dietary intake of renal stone patients. II. Urine biochemistry and stone analysis.

The dietary intakes of 88 renal stone cases and 88 age and sex matched controls were assessed by dietary history using a standardised questionnaire. The stone cases were divided into six subgroups established on the basis of urine biochemistry (calcium, oxalate and uric acid) and stone composition. The average intake of each group was then compared with that of their controls using standard statistical procedures. Cases with idiopathic calcium oxalate stones had significantly lower intakes of dietary fibre, non-cellulose polysaccharide, phytate, magnesium, phosphate and thiamine than controls. No significant difference in dietary intake was found between cases with high urinary calcium and uric acid and their respective controls. All cases with a high urinary oxalate had a significantly higher intake of vitamin C than controls. Our results support the belief that dietary intake is an important pre-urinary risk factor of idiopathic renal stone disease.