A control study of dietary factors in renal stone formation

Dietary habits in women with recurrent idiopathic calcium nephrolithiasis

Background

Nutrition has been widely recognized to influence the risk of kidney stone formation. Therefore the aim of our study was to assess: a) whether usual diet of women with idiopathic calcium nephrolithiasis (ICN) living in Parma (Northern-Italy) is different compared to healthy controls, b) how their diet differs from Italian National guidelines and c) whether it is related to nephrolithiasis clinical course.

Methods

143 women with recurrent ICN (mean age 43 ± 13 ys) and 170 healthy women (mean age 42 ± 11 ys) were enrolled. All women completed a food frequency questionnaire for the last 60-days and a 3-day dietary diary analysed with a dedicated software.

Results

Stone formers showed a higher consumption of sausages, ham, meat and sweets than healthy controls (43.1% vs 11.1%, 29.4% vs 13.9%, 21.6% vs 4.2%, 66.7% vs 18.1%, p < 0.001). The 3-day diary analysis showed an intake of calories, carbohydrates, lipids and non-discretionary sodium about 10% higher than healthy controls (p < 0.001). Finally, after dividing the population into 3 age groups (≤30, 31-40, > 40 years), the differences described above were amplified in the class ≤30 years, where nephrolithiasis presented a more serious course (shorter recurrence interval, greater stone-rate). In this age group the intake of fruit and vegetables was notably lower than guideline recommendations.

Conclusions

We conclude that the usual diet of women with recurrent ICN is different from controls and characterized by low intake of fruits and vegetables and higher consumption of simple sugars and foods with high protein and salt content. This dietary imbalance could play a role in the ICN pathogenesis, especially in younger women.

This work was financed by grants from Italian Ministry of University and Research as part of a larger project about the prevention of kidney stones (PRIN 2005063822) and by Fondazione per la Ricerca Scientifica Termale (FoRST). No potential conflict of interest relevant to this paper was reported.

Intestinal transport of an obdurate anion: oxalate

In this review, we focus on the role of gastrointestinal transport of oxalate primarily from a contemporary physiological standpoint with an emphasis on those aspects that we believe may be most important in efforts to mitigate the untoward effects of oxalate. Included in this review is a general discussion of intestinal solute transport as it relates to oxalate, considering cellular and paracellular avenues, the transport mechanisms, and the molecular identities of oxalate transporters. In addition, we review the role of the intestine in oxalate disease states and various factors affecting oxalate absorption.

Idiopathic calcium oxalate urolithiasis: risk factors and conservative treatment

Idiopathic calcium oxalate urolithiasis is a frequent and recurrent multifactorial disease. This review focuses on urinary and dietary risk factors for this disease and conservative strategies for rectifying them. Dietary oxalate and calcium and their respective urinary excretions have been extensively investigated during the last 10 years. Urinary oxalate has emerged as the most important determinant of calcium oxalate crystallization while the role of urinary calcium has shifted to bone balance and osteoporosis. Dietary calcium restriction increases urinary oxalate and contributes to a negative bone balance. It has therefore been abandoned as a means to reduce the risk of calcium oxalate kidney stone formation. Calcium oxalate kidney stone patients are advised to increase their fluid intake to achieve a urine volume of 2 l or more; the recommended calcium intake is 800-1200 mg/day; high oxalate foods should be restricted; daily protein intake should be between 0.8 and 1 g/kg body weight/day; essential fats should be included; vegetable and fruit (except oxalate-rich vegetables) intake should be increased. The use of calcium supplements has potential benefits but needs to be examined further.

Effects of dietary fat on the urinary risk factors of calcium stone disease

OBJECTIVES

To assess the association between dietary fat and various urinary risk factors of calcium stone disease in a group of calcium stoneformers attending an outpatient stone clinic.

METHODS

Mean daily fat intake from self-recorded 4-day dietary food records and mean 24-hour urinary risk factors from two separate collections were evaluated in 476 patients selected randomly from an adult population attending an outpatient stone clinic for the first time.

RESULTS

Mean daily total fat intake for men and women was significantly different at 105.6 and 78.1 g, respectively. Examination of the relationship between total fat intake and 24-hour urinary volume, pH, and excretions of magnesium, citrate, oxalate, calcium, and uric acid revealed no significant regressions in men and only a weak association between fat intake and urinary uric acid in women.

CONCLUSIONS

Dietary fat does not have a significant effect on the urinary risk factors of calcium stone disease.

Effects of low animal protein or high-fiber diets on urine composition in calcium nephrolithiasis

BACKGROUND

The purpose of this article is to evaluate the impact of low protein and high fiber intakes on risk factors of stone recurrence in idiopathic calcium stone formers (ICSFs).

METHODS

Ninety-six ICSFs were randomly assigned a low animal protein diet (< 10% of total energy), a high-fiber diet (> 25 g/day), or a usual diet (control group); all patients were recommended to increase their fluid intake. Their daily urine compositions were analyzed at baseline and at four months. Compliance with dietary recommendations was checked by validated food frequency questionnaires. Compliance with total and animal protein intakes was assessed by 24-hour urea and sulfate outputs, respectively. The nutritional intervention (oral instructions, written leaflet, phoning) and food assessment were carried out by a research dietitian.

RESULTS

At baseline, diets and the daily urine composition did not differ between the three groups. At four months, while diets differed significantly, the 24-hour output of calcium and oxalate did not differ significantly within and between groups after adjustment for potential confounders (age, sex, and personal and family history of calcium stones) and baseline values. However, as many as 12 out of 31 ICSFs (95% CI, 22 to 58%) assigned to a low animal protein diet achieved a reduction in the urine urea excretion rate of more than 50 mmol/day and also exhibited a significant decrease in urinary calcium excretion that averaged 1.8 mmol/day. A significant correlation between urea and calcium outputs was observed only among patients with hypercalciuria.

CONCLUSIONS

These results show that only ICSFs who markedly decrease their animal protein intake, especially those with hypercalciuria, can expect to benefit from dietary recommendations.

Effect of dietary intake on urinary oxalate excretion in calcium renal stone formers

OBJECTIVE

To investigate the influence of dietary intake on urinary oxalate excretion in calcium renal-stone formers.

PATIENTS AND METHODS

Dietary intake was monitored by using the dietary-record method in 60 idiopathic stone formers. The patients collected their urine for 24 h at home and their urinary oxalate excretion rate was determined. The relationship between the daily intake of various nutrients and urinary oxalate excretion was examined by both monovariate and multivariate analyses.

RESULTS

By monovariate analysis, the intake of carbohydrate, total protein and fat were significantly correlated with urinary oxalate excretion, but the intake of calcium and body surface area were not. In addition, the intake of total protein was highly correlated with that of fat. By multivariate analysis, the intake of carbohydrate and fat were significantly related to urinary oxalate excretion, and the intake of calcium was inversely correlated with urinary oxalate excretion, but the intake of total protein showed no significant correlation.

CONCLUSION

The intake of carbohydrate and fat was positively and the intake of calcium was inversely correlated with urinary oxalate excretion in stone formers and, taken together, these findings suggested that fat plays an important role in urinary oxalate excretion and that protein has a minimal effect.

A prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones

BACKGROUND

A high dietary calcium intake is strongly suspected of increasing the risk of kidney stones. However, a high intake of calcium can reduce the urinary excretion of oxalate, which is thought to lower the risk. The concept that a higher dietary calcium intake increases the risk of kidney stones therefore requires examination.

METHODS

We conducted a prospective study of the relation between dietary calcium intake and the risk of symptomatic kidney stones in a cohort of 45,619 men, 40 to 75 years of age, who had no history of kidney stones. Dietary calcium was measured by means of a semiquantitative food-frequency questionnaire in 1986. During four years of follow-up, 505 cases of kidney stones were documented.

RESULTS

After adjustment for age, dietary calcium intake was inversely associated with the risk of kidney stones; the relative risk of kidney stones for men in the highest as compared with the lowest quintile group for calcium intake was 0.56 (95 percent confidence interval, 0.43 to 0.73; P for trend, < 0.001). This reduction in risk decreased only slightly (relative risk, 0.66; 95 percent confidence interval, 0.49 to 0.90) after further adjustment for other potential risk factors, including alcohol consumption and dietary intake of animal protein, potassium, and fluid. Intake of animal protein was directly associated with the risk of stone formation (relative risk for men with the highest intake as compared with those with the lowest, 1.33; 95 percent confidence interval, 1.00 to 1.77); potassium intake (relative risk, 0.49; 95 percent confidence interval, 0.35 to 0.68) and fluid intake (relative risk, 0.71; 95 percent confidence interval, 0.52 to 0.97) were inversely related to the risk of kidney stones.

CONCLUSIONS

A high dietary calcium intake decreases the risk of symptomatic kidney stones.

Environmental factors in the pathophysiology of recurrent idiopathic calcium urolithiasis (RCU), with emphasis on nutrition

A number of environmental factors are under discussion as possibly implicated in the etiology of RCU. On the basis of data in the literature and our own results, we attempted a critical weighting up of the possible contributions of climate, pollution, stress, nutrition in general and especially oxalate and minerals in the nutrition. It was concluded that there is a need for more in-depth research into the response of the body to challenges from the environment, in particular nutrition.

The influence of diet on urinary risk factors for stones in healthy subjects and idiopathic renal calcium stone formers

The daily intake of 103 recurrent idiopathic calcium stone formers and 146 controls was assessed by means of a computer-assisted 24-h dietary record. Timed 24-h urine samples were collected over the same period to assess the relationship between dietary intake of nutrients and urinary risk factors for calcium stones. After standardisation for sex, age and social status a total of 128 subjects underwent final statistical analysis; 64 renal stone formers and 64 controls. Significant increases in the consumption of animal and vegetable protein and purine were identified as the nutritional factors that distinguished renal stone formers from controls. As expected, the daily urinary excretion of calcium and oxalate was higher and the daily urinary excretion of citrate was lower in stone formers than in controls. No difference with respect to daily urinary uric acid excretion was recorded. Daily urinary excretion of calcium was correlated to dietary protein intake while daily urinary oxalate was correlated to dietary vitamin C intake. It was concluded that renal stone formers could be predisposed to stones because of their dietary patterns. A link between the protein content of the diet and urinary calcium was confirmed, but dietary animal protein had a minimal effect on oxalate excretion.

Do stone formers have lower urinary fibrinolytic activity than controls?

A comparison of urinary fibrinolytic activity between 31 stone formers and 50 controls failed to demonstrate any significant difference and so failed to confirm an earlier independent observation. This may be due to methodological and design differences between the 2 studies, but does suggest reservations about the significance of lowered urinary fibrinolytic activity as a risk factor for renal stone disease. Dietary information from those taking part in the study suggests that a reduction of meat intake by stone formers might be associated with increased urinary fibrinolytic activity. This might account for the discrepancy between the 2 studies, in which case this observation could be of significance.

Clinical effects of prophylactic dietary treatment on renal stones

From the investigation of the dietary intake and habits of male Japanese renal stone patients we established several general guidelines. Fluid intake should be increased, especially after dinner. Unbalanced diets should be corrected and avoided (the diet should include different types of food, with vegetables being eaten at every meal and an excessive intake of meat should also be avoided). Three meals a day should be eaten and an excessive intake at dinner should be avoided. The interval from dinner until retiring should be extended. By following these individual dietary guidelines the stone recurrence rate in 199 male calcium stone patients who had received individual dietary instruction decreased remarkably compared to that in male calcium stone patients who had not received individual dietary instruction, not only during the period of outpatient visits but also after outpatient visits were discontinued. From these results we conclude that individual dietary management should be the primary measure for the prophylaxis of renal stone disease in Japan.

Effect of unprocessed wheat bran on calciuria and oxaluria in patients with urolithiasis

Seventeen hypercalciuria patients (8 control, 9 treatment) with a history of urolithiasis were randomly selected to receive low-calcium, low-oxalate diets with or without the addition of 30 g of dietary fiber as unprocessed wheat bran. Diet alone resulted in a 5.6 percent decrease in calciuria compared with a 23.5 percent decrease with the addition of the fiber. The addition of hydrochlorothiazide and potassium citrate further reduced calciuria by 40.4 percent and 34.5 percent, respectively. Oxaluria was decreased 21.4 percent by diet alone compared with 3.9 percent in the diet and fiber treatment group. Patient compliance to diets was good, and no complications resulted from fiber intake.

Dietary habits in renal stone patients compared with healthy subjects

The dietary habits of renal calcium stone patients were investigated both by dietary history and by 4-day food records and compared with the dietary habits of control subjects, matched on the basis of age, sex, social and professional status. The method using 4-day records seemed to be more precise, judged by the correlation to the urinary output of nutrients. There was no difference in the daily intake of major nutrients between stone formers and controls, but a higher ingestion of vitamin C in controls and a larger consumption of alcohol among stone formers. In contrast to some epidemiological evidence, there were no significant differences in consumption of animal protein when stone formers were matched for social class. Despite a similar total intake of calcium, the stone formers excreted more calcium in the urine, probably reflecting a higher intestinal absorption of calcium. There seem to be only marginally different dietary habits between stone formers and carefully matched control subjects. Differences in the urinary output of minerals and electrolytes are mainly due to variations in gastrointestinal uptake.

Calcium metabolism in normal and in hypercalciuric patients on Farnolith, a dietary fibre preparation

In the present study Farnolith (a granular powder consisting of different dietary fibres) was given to normals (n = 6), patients suffering from absorptive hypercalciuria type I (n = 6) and to one patient suffering from renal hypercalciuria. Farnolith binds calcium and reduces the calcium absorption from the intestine. In normals the urine- and serum parameters of calcium metabolism (total- and ionised calcium, parathyroid hormone and vitamin-D-metabolites) remained unchanged. In patients suffering from absorptive hypercalciuria type I a significant reduction of hypercalciuria was found; oxalic acid excretion had decreased as well. Lowered parathyroid hormone values returned to normal, vitamin-D-metabolites remained unaffected. In one patient suffering from renal hypercalciuria parathyroid hormone and 1,25-dihydroxy-vitamin D values increased, calcium excretion had not decreased, though. Our investigation shows that Farnolith is suitable for the treatment of absorptive hypercalciuria. Calcium homoeostasis is returned to normal by Farnolith, at the same time it does not produce secondary hyperoxaluria (as e.g. sodium cellulose phosphate). Patients with primary renal calcium loss should not be treated by Farnolith.

Unprocessed bran and intermittent thiazide therapy in prevention of recurrent urinary calcium stones

Both urinary calcium excretion and renal stone episodes are increased during the summer in Finland. Since thiazide and unprocessed bran are known to decrease urinary calcium excretion, we treated 73 patients with recurrent urinary stone formation by giving them unprocessed bran and intermittent thiazide. Of the patients, 32 had absorptive hypercalciuria and 41 had normal urinary calcium values. All patients were on a low-calcium and low-oxalate diet and took 40 g bran daily. Fourteen of the hypercalciuric and 14 of the normocalciuric patients were randomly allocated to use hydrochlorothiazide 50 mg b.i.d. from May to September. Reduction of stone formation was seen in all groups. The combination of thiazide + bran was superior to the bran on its own in inhibition of stone formation. Only 3/11 (27%) stones passed through during the summer in the thiazide + bran group as compared with the 11/17 (65%) in the bran group.

Risk factors for renal stone formation in patients with spinal cord injury

To determine factors that may influence kidney stone formation in spinal cord injury patients, the medical records of 893 patients who had been followed up by the Milwaukee Veterans Administration Medical Center from 1970 to 1984 were extensively reviewed. Urography showed that 12 patients had kidney stones. Twenty-four non-kidney stone patients with a similar age range, sex and duration of time since injury were selected as controls. Variables, such as level of spinal lesion, completeness of neurological dysfunction, presence of ureteric reflux etc, were compared and analysed statistically. The results showed that there was no difference between patients with and those without renal stone as far as the level of spinal injury and completeness of spinal cord lesion were concerned. There was no relationship between kidney stone formation and methods of urinary drainage or the presence of ureteric reflux. However, patients with good bladder control had no renal calculi. Serum creatinine, phosphorus, uric acid and calcium levels were similar in both groups of patients. There was a relationship between sepsis, positive urine culture and kidney stone formation. The absence of physical activity was not a risk factor for renal calculi and patients on a high fibre diet had the same incidence of stones as those on a regular diet.

Medical investigation and treatment of urinary stones: a search for new ideas

The main threads of recent research into the cause and treatment of calcium oxalate/phosphate stones are reviewed. Little progress has been made in recent years, and two main reasons can be identified. First, there has been too much emphasis upon calcium and too little emphasis upon urinary oxalate as causative factors. Second, there has been too much emphasis upon the physical chemistry of simple solutions and too little emphasis upon the study of whole urine.

A case-control study of dietary intake of renal stone patients. I. Preliminary analysis

The average daily dietary intake of 88 idiopathic renal stone cases and 88 age and sex matched controls was assessed by history using a standardised questionnaire. Statistical analysis was undertaken on the whole group and on male and female subgroups, to establish if there were any significant differences between cases and controls. There were statistically significant differences in dietary intake between the whole group, the female cases and the control group. Male cases showed only a significantly lower intake of thiamine compared to controls. There was little difference between cases and controls intake of iron or multivitamin supplements but vitamin C supplements (greater than 1 g/day) were taken more than twice as frequently by cases than controls. These results suggest that control dietary studies of renal stone patients without regard to their sex may conceal many differences in dietary intake between cases and controls.

Effects of High Intake of Dietary Animal Protein on Mineral Metabolism and Urinary Supersaturation of Calcium Oxalate in Renal Stone Formers

The metabolic effects of a high protein diet (HPD) were studied in eight patients with idiopathic recurrent calcium oxalate stones. On the HPD there was a 35% increase in urinary calcium concomitant with increased excretion of cyclic AMP and hydroxyproline. These findings point to an enhanced resorption of bone, possibly secondary to increased renal loss of calcium. The urinary citrate decreased by 25% along with reduced serum standard bicarbonate and urinary pH. The high formation of acid metabolites might also have adverse effects on calcium balance and bone. Urinary oxalate excretion was not affected nor were there any significant changes in the calculated urinary supersaturation of calcium oxalate, if changes in urinary citrate, pH, sulphate, sodium, phosphate and volume were also considered. This study suggests that the possible negative influence on the propensity to form renal stones of a diet rich in animal protein is probably due to reduced urinary inhibitory activity.

Rice bran treatment for hypercalciuric patients with urinary calculous disease

We report on the efficacy of rice bran in hypercalciuric patients with urinary calculous disease. After the administration of defatted rice bran at a dosage of 20 gm. daily for 4 weeks urinary calcium excretion was reduced significantly from 402 plus or minus 102 to 291 plus or minus 123 mg. per 24 hours. In 6 patients who showed a reduction of urinary calcium excretion an increase in urinary calcium excretion was observed 4 weeks after stopping the administration. All 7 patients who previously received defatted rice bran were given processed or rice bran free of phytin at a dosage of 20 gm. daily. The value of urinary calcium excretion increased again during the administration of processed rice bran but was less marked than that of the preceding 6 patients. Although it is interesting to debate whether the influence of rice bran on the urinary calcium excretion depends on the action of phytin or of other constituents defatted rice bran should be effective in reducing urinary excretion of calcium. These results would come up to the expectations of the patients with recurrent urinary calculous disease.

Dietary management of urinary risk factors in renal stone formers

Three hundred and ninety-two stone formers were investigated to exclude systemic disorders and to define the presence of haematological and urinary abnormality commonly associated with stone disease. Increased urinary excretion of calcium, oxalate or uric acid was found in 40% and there was more than one abnormality in 16% of the patients. The dietary habit of stone formers did not differ significantly from that of control subjects. Dietary advice to increase the consumption of fibre and reduce the consumption of sugar, refined carbohydrates and animal protein produced a significant reduction in the urinary excretion of calcium, oxalate and uric acid. We consider that reduction of the nutrient density of the diet by this means is the first line of management of idiopathic stone formers.