Wheat bran in the selective therapy of absorptive hypercalciuria: a study performed on 18 lithiasic patients

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.

Role of Nutrition in the Formation of Calcium-Containing Kidney Stones

Diet plays an important role in the pathogenesis of calcium-containing kidney stones. Although much work has demonstrated that specific dietary components alter urinary composition and supersaturation, relatively few studies link the ingestion of these components with actual nephrolithiasis. This article reviews the dietary factors thought to promote or inhibit the formation of calcium stones and discusses the current controversies in the field of nutrition and nephrolithiasis. Special attention is paid to the roles of dietary calcium, supplemental calcium, oxalate, phytate, and n-3 fatty acids. We offer dietary recommendations to individuals who have suffered from a calcium-containing kidney stone, and emphasize that a patient's 24-hour urine chemistries should be used to help guide dietary intervention.

Potassium and sodium intake and excretion in calcium stone forming patients

OBJECTIVE

To determine mean potassium (K) intake and its correlation with urinary calcium (uCa) and citrate excretion, as well as uCa, sodium (Na), and K levels of calcium stone forming patients. We determined the K-rich foods most commonly consumed by these patients.

DESIGN

Case-control.

SETTING

University-affiliated outpatient renal Lithiasis Unit.

PATIENTS AND CONTROLS

One hundred hypercalciuric calcium stone forming patients (CSF, 54 men/46 women), 37 with associated hypocitraturia, were sequentially enrolled in the study that was performed before the initiation of any care for their renal stones. The control group consisted of 100 age-matched healthy subjects (HS, 47 men/53 women) who were laboratory employees with no history of renal stones.

INTERVENTION

The analyses consisted of a 3-day dietary record to determine the mean K and calcium (Ca) intakes, and a 24-hour urine sample with measurements of K, Ca, Na, and citrate.

MAIN OUTCOME MEASURE

K and Na intake determined by dietary record.

RESULTS

uCa and Na levels and the Na/K ratio were significantly higher for CSF versus HS (238 +/- 118 v 148 +/- 74 mg/24 hours, 238 +/- 100 v 181 +/- 68 mEq/24 hours, 6.6 +/- 3.5 v 5.1 +/- 2.3, respectively, P < .05). The mean citrate excretion was lower in CSF than in HS patients (410 +/- 265 v 530 +/- 240 mg/24 hours). Mean uCa did not differ between groups. CSF patients showed a higher sodium chloride intake compared with HS (14 +/- 4 vs 8 +/- 3 g/day). The mean Ca intake of CSF and HS were 559 +/- 327 and 457 +/- 363 mg/day, respectively. The mean K intake of CSF and HS were 58 +/- 17 and 51 +/- 27 mEq/day. A positive correlation was observed between uCa and urinary sodium (r = .40 and r = .65, P < .05), urinary potassium and urinary citrate (r = .25 and r = .53, P < .05), uCa and Na/K (r = .33 and r = .56, P < .05) respectively for CSF and HS. The following were the K-rich foods consumed at least once a day by these groups: beans (by 70% of CSF and 75% of HS), tomatoes (by 42% of CSF and 50% of HS), oranges (by 30% of CSF and 55% of HS), and bananas (by 42% of CSF and 23% of HS).

CONCLUSION

Despite the consumption of K-rich foods at least once a day, the mean K intake by CSF patients was 58 mEq/day. This intake can still be considered to be low, although it meets recommended daily dietary allowance requirements. Therefore, we describe herein a population of CSF with high-Na intake and normal- to low-K intake, which may contribute to stone formation.

Effect of dietary rhubarb stalk fiber on the bioavailability of calcium in rats

Ground rhubarb stalk fiber containing, on a dry weight basis, 74% total dietary fiber (66% insoluble and 8% soluble) was prepared from rhubarb plants. This fiber source has been shown to have a pronounced lipid lowering effect in mice. Its high oxalic acid content may, however, be a limiting factor for its use. The present study was undertaken to determine the safe dose level of the fiber in terms of its effect on calcium bioavailability. Male weanling Sprague-Dawley rats were fed a semi-purified diet (AIN 76) for 4 weeks containing 0, 1, 3, or 5% rhubarb fiber, or pure oxalic acid equivalent to 5% rhubarb fiber. The fiber content of each diet was brought to 5% by adding cellulose, and the calcium level of all diets was the same. As the rhubarb stalk fiber content of the diet increased, a consistent trend of increasing total retention and apparent absorption of calcium was manifested. In contrast, however, cellulose, due to its increased effect on intestinal motility resulted in a decreased calcium bioavailability. Overall results suggest that an addition of rhubarb stalk powder up to the level of 5% in a diet does not have detrimental effect on calcium bioavailability.

Results of long-term rice bran treatment on stone recurrence in hypercalciuric patients

A series of 182 calcium stone formers with idiopathic hypercalciuria underwent treatment with rice bran for 1 to 94 months. Urinary calcium excretion was considerably reduced, but there was some increase in urinary phosphate and oxalate. Urinary excretion of magnesium and uric acid, serum calcium, magnesium, phosphate, uric acid, parathyroid hormone (PTH) and ALP was unaffected. There were no obvious changes in serum iron, zinc and copper even when patients were treated for long periods. Rice bran was well tolerated in almost all cases and there were no serious side effects; 49 patients have undergone treatment for more than 3 years (average duration of administration 5.09 years). The frequency of new stone formation was drastically reduced (individual stone formation rate (no./year) from 0.720 +/- 0.533 to 0.125 +/- 0.204; group stone formation rate (no./patient-year) from 0.721 to 0.120) compared with the 3-year period before treatment. During treatment, 61.2% of patients remained in remission. Although rice bran therapy should be effective in correcting absorptive hypercalciuria, there may be limits to the overall ability of rice bran monotherapy to prevent recurrence.