Effect of calcium intake on urinary oxalate excretion in calcium stone-forming patients

Abstract

Dietary calcium lowers the risk of nephrolithiasis due to a decreased absorption of dietary oxalate that is bound by intestinal calcium. The aim of the present study was to evaluate oxaluria in normocalciuric and hypercalciuric lithiasic patients under different calcium intake. Fifty patients (26 females and 24 males, 41 ± 10 years old), whose 4-day dietary records revealed a regular low calcium intake (≤500 mg/ day), received an oral calcium load (1 g/day) for 7 days. A 24-h urine was obtained before and after load and according to the calciuria under both diets, patients were considered as normocalciuric (NC, N = 15), diet-dependent hypercalciuric (DDHC, N = 9) or diet-independent hypercalciuric (DIHC, N = 26). On regular diet, mean oxaluria was 30 ± 14 mg/24 h for all patients. The 7-day calcium load induced a significant decrease in mean oxaluria compared to the regular diet in NC and DIHC (20 ± 12 vs 26 ± 7 and 27 ± 18 vs 32 ± 15 mg/24 h, respectively, P<0.05) but not in DDHC patients (22 ± 10 vs 23 ± 5 mg/ 24 h). The lack of an oxalate decrease among DDHC patients after the calcium load might have been due to higher calcium absorption under higher calcium supply, with a consequent lower amount of calcium left in the intestine to bind with oxalate. These data suggest that a longlasting regular calcium consumption <500 mg was not associated with high oxaluria and that a subpopulation of hypercalciuric patients who presented a higher intestinal calcium absorption (DDHC) tended to hyperabsorb oxalate as well, so that oxaluria did not change under different calcium intake.

Influence of a low- and a high-oxalate vegetarian diet on intestinal oxalate absorption and urinary excretion

“…These divalent cations are able to bind oxalate. The resulting sparingly soluble salts prevent absorption and are excreted with faeces (Liebman and Costa, 2000;Nishiura et al, 2002;von Unruh et al, 2004). Because of the fact that both vegetarian diets had the same content of fluids and nutrients, including calcium and magnesium, we expected urinary oxalate excretion and possibly oxalate Vegetarian diet: influence on oxalate absorption and urinary oxalate excretion E Thomas et al absorption to be higher on the high-oxalate vegetarian diet than on the low-oxalate vegetarian diet, as it is known that higher intake of oxalate results in higher urinary oxalate excretion (Binder, 1974;Holmes et al, 1995Holmes et al, , 2001Zimmermann et al, 2005) and that it can also lead to an increase in the percent oxalate absorption for soluble oxalate (Zimmermann et al, 2005).…”

Fat malabsorption induced by gastrointestinal lipase inhibitor leads to an increase in urinary oxalate excretion

“…Intestinal hyperabsorption of oxalate caused solely by high oxalate intake is controversial [5,[42][43][44] but the imbalance between intraluminal calcium and oxalate caused by a low-calcium diet, absorptive hypercalciuria, or enteric hyperoxaluria is incontrovertible [10,13,45].…”

“…Secondary hyperoxaluria is due to either increased availability of substrate (ascorbic acid, ethylene glycol, methoxyflurane) [8] or to intestinal hyperabsorption of oxalate caused by a high oxalate diet, enteric hyperoxaluria, or an imbalance between intraluminal calcium and oxalate as in a lowcalcium diet [9][10][11][12][13].…”

Formación de calculos renales de oxalato cálcico en mamíferos

“…Por su parte, en perros y gatos la oxaluria se asocia a nefrosis por Ox más que a urolitiasis de CaOx (Buffington, 1998;Stevens y Brenner, 1996). La SHO resulta de un aumento en la disponibilidad de sustrato como ácido ascórbico, etilenglicol y metoxifluorano (Conyers et al, 1990) (Marangella et al, 1982;Curhan et al, 1993;Massey y Sutton, 1993;Takei et al, 1998;Nishiura et al, 2002).…”