Objectives: To examine the relationship between 12 macro- and micro-nutrients and the risk of recurrent calcium stone formation by comparing the diets of a large outpatient clinic-based group of patients who had formed calcium-based urinary tract calculi with that of a population-based control group matched for age, gender and body mass index.
Patients, subjects and methods: The dietary intake of 500 patients (cases) randomly selected from the adult population attending an outpatient renal-stone clinic and being evaluated and/or treated for biochemically or radiologically diagnosed calcium-based upper urinary tract calculi were compared with those of 500 control subjects selected to match for age, sex and body mass index from a stratified probability sample of 2212 adults (not institutionalized) living in the same geographical area.
Results: Comparing the mean nutritional intakes showed a statistically higher consumption of energy, carbohydrates, sodium, fibre, vitamin C, fat and folic acid among cases than in controls. The intake of calcium, alcohol and vitamin A was significantly higher among the controls. There were no significant differences in the intake of protein, niacin or iron. The results of these comparisons varied when the groups were stratified by sex, age and body mass index.
Conclusions: Dietary risk factors for calcium-based urinary tract calculi are many and complex, and a detailed consideration of sex, age and body mass index is important in interpreting such data. While it is difficult to draw firm conclusions about causes and effects of individual nutrients from the available data, this study indicates a possibly more important role for dietary fat in stone formation than has been previously recognized. This relationship needs to be further explored in relation to urinary risk factors, as it may be possible to advise patients to reduce dietary fat as a prophylactic measure for stone formation. As dietary fat has been associated with cardiovascular diseases and possibly cancer, an overall recommendation to these patients for a low dietary fat intake may be easier to follow.