Contribution of dietary oxalate to urinary oxalate excretion

Holmes, Ross P.; Goodman, Harold S.; Assimos, Dean G.

doi:10.1046/j.1523-1755.2001.00488.x

Cited by 427 publications

(332 citation statements)

References 22 publications

Supporting

Mentioning

307

Contrasting

Unclassified

Order By: Relevance

“…Indeed, increased absorption of dietary oxalate may be observed in up to one third of patients with calcium oxalate nephrolithiasis. 12 Another study found that mean oxalate absorption in normal volunteers was 8%, compared with 10.2% in a group of calcium oxalate stone formers. 26 Some data suggest that differential rates of colonization by Oxalobacter formigenes, an enteric oxalate-degrading organism, may be responsible for such variation.…”

Section: Discussionmentioning

confidence: 97%

“…The proportion of urinary oxalate that is derived from dietary oxalate is unclear: estimates range from 10 to 50%. 12 However, it is well established that a large proportion of urinary oxalate is derived from the endogenous metabolism of glycine, glycolate, hydroxyproline, and dietary vitamin C. 10,11 A recent metabolic study compared a controlled diet with 25% of protein from gelatin (2.75 g of hydroxyproline) with the same diet except with 25% of protein from whey (containing no hydroxyproline). 22 The diet that was high in hydroxyproline increased urinary oxalate excretion by 42%.…”

Section: Discussionmentioning

confidence: 99%

“…9 Uncertainty about the impact of dietary oxalate on stone risk centers around the contribution of oxalate intake to urinary oxalate excretion. A large amount of urinary oxalate is derived from the endogenous metabolism of glycine, glycolate, hydroxyproline, and dietary vitamin C, 10,11 and the proportion of urinary oxalate derived from dietary oxalate is unclear (estimates range from 10 to 50% 12 ). Studies of dietary oxalate and stone risk also must account for the intake of other dietary factors.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Oxalate Intake and the Risk for Nephrolithiasis

Taylor

Curhan

2007

Journal of the American Society of Nephrology

179

116

View full text Add to dashboard Cite

Most kidney stones consist of calcium oxalate, and higher urinary oxalate increases the risk for calcium oxalate nephrolithiasis. However, the relation between dietary oxalate and stone risk is unclear. This study prospectively examined the relation between oxalate intake and incident nephrolithiasis in the Health Professionals Follow-up Study (n ϭ 45,985 men), the Nurses' Health Study I (n ϭ 92,872 older women), and the Nurses' Health Study II (n ϭ 101,824 younger women). Food frequency questionnaires were used to assess oxalate intake every 4 yr. Cox proportional hazards regression was used to adjust for age, body mass index, thiazide use, and dietary factors. A total of 4605 incident kidney stones were documented over a combined 44 yr of follow-up. Mean oxalate intakes were 214 mg/d in men, 185 mg/d in older women, and 183 mg/d in younger women and were similar in stone formers and non-stone formers. Spinach accounted for Ͼ40% of oxalate intake. For participants in the highest compared with lowest quintile of dietary oxalate, the relative risks for stones were 1.22 (95% confidence interval [CI] 1.03 to 1.45; P ϭ 0.01 for trend) for men and 1.21 (95% CI 1.01 to 1.44; P ϭ 0.05 for trend) for older women. Risk was higher in men with lower dietary calcium (P ϭ 0.08 for interaction). The relative risks for participants who ate eight or more servings of spinach per month compared with fewer than 1 serving per month were 1.30 (95% CI 1.08 to 1.58) for men and 1.34 (95% CI 1.10 to 1.64) for older women. Oxalate intake and spinach were not associated with risk in younger women. These data do not implicate dietary oxalate as a major risk factor for nephrolithiasis. Kidney stones are common, costly, and painful. The lifetime prevalence of symptomatic nephrolithiasis is approximately 10% in men and 5% in women, 1,2 and more than $2 billion is spent on treatment each year. 3,4 Approximately 80% of kidney stones contain calcium, and the majority of calcium stones consist primarily of calcium oxalate. 5 Small increases in urinary oxalate can have a major effect on calcium oxalate crystal formation, 6 and higher levels of urinary oxalate are a major risk factor for the formation of calcium oxalate kidney stones. 5,7 Because oxalate is a metabolic end product and is excreted unchanged in the urine after absorption in the gastrointestinal tract, clinicians routinely recommend a low-oxalate diet to patients with calcium oxalate nephrolithiasis. 8 However, the role of dietary oxalate in the pathogenesis of calcium oxalate nephrolithiasis is unclear. 9 Uncertainty about the impact of dietary oxalate on stone risk centers around the contribution of oxalate intake to urinary oxalate excretion. A large amount of urinary oxalate is derived from the endogenous metabolism of glycine, glycolate, hydroxyproline, and dietary vitamin C, 10,11 and the proportion of urinary oxalate derived from dietary oxalate is unclear (estimates range from 10 to 50% 12 ). Studies of dietary oxalate and stone risk also must account for the intake...

show abstract

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Oxalate Intake and the Risk for Nephrolithiasis

Taylor

Curhan

2007

Journal of the American Society of Nephrology

179

116

View full text Add to dashboard Cite

show abstract

“…Evidence from our laboratory indicates that approximately half of urinary oxalate is derived from the diet, a key environmental factor [2]. While the concentration of oxalate in urine will affect its super-saturation with calcium oxalate and thus stone growth, it is not clear what role the amount of oxalate ingested, the amount of oxalate absorbed, or the renal handling of oxalate play in stone formation.…”

Section: Introductionmentioning

confidence: 99%

Intestinal and renal handling of oxalate loads in normal individuals and stone formers

2007

Self Cite

View full text Add to dashboard Cite

The renal handling and intestinal absorption of dietary oxalate are believed to be risk factors for calcium oxalate stone formation. In this study, we have examined the time and dose effects of soluble oxalate loads on the intestinal absorption and renal handling of oxalate in six stone formers (SF) and six normal individuals (N) who consumed diets controlled in oxalate and other nutrients. Urinary and plasma oxalate changes were monitored over 24 h after ingestion of 0, 2, 4, and 8 mmole oxalate loads, containing a mixture of 12 C-and 13 C 2 -oxalate. There were significant time and dose dependent changes in urinary oxalate excretion and secretion after these loads. However, there were no significant differences between SF and N in both the intestinal absorption and the renal handling of oxalate loads, as measured by the urinary excretion of oxalate (P = 0.96) and the ratio of oxalate to creatinine clearance (P = 0.34). 13 C 2 -oxalate absorption studies showed three of the subjects, two SF and one N, had enhanced absorption with the 8 mmole load. A clear difference in absorption was demonstrated in these individuals during the 8-24 h interval, suggesting that in these individuals there was greater oxalate absorption in the large intestine as compared to the other subjects. This enhanced absorption of oxalate warrants further characterization.

show abstract

“…The reason why these contradictory and confusing recommendations persisted for so long is the lack of prospective studies and the fact that analysis of oxalate remained unreliable (4) until the mid-1980s. Consequently, the amount of dietary oxalate excreted in urine and its role for renal stone formation were underestimated (5). The fact that a low-Ca diet emerged as a risk factor for Ca oxalate calculi and that a high-Ca diet emerged as a protective factor in two large epidemiologic studies (6,7) is still frequently ignored.…”

mentioning

confidence: 99%

Dependence of Oxalate Absorption on the Daily Calcium Intake

Unruh¹,

Voß

Sauerbruch³

et al. 2004

Journal of the American Society of Nephrology

142

View full text Add to dashboard Cite

Abstract. Two to 20% of ingested oxalate is absorbed in the gastrointestinal tract of healthy humans with a daily 800 mg calcium intake. Calcium is the most potent modifier of the oxalate absorption. Although this has been found repeatedly, the exact correlation between calcium intake and oxalate absorption has not been assessed to date. Investigated was oxalate absorption in healthy volunteers applying 0.37 mmol of the soluble salt sodium [ 13 C 2 ]oxalate in the calcium intake range from 5 mmol (200 mg) calcium to 45 mmol (1800 mg) calcium. Within the range of 200 to 1200 mg calcium per day, oxalate absorption depended linearly on the calcium intake. With 200 mg calcium per day, the mean absorption (Ϯ SD) was 17% Ϯ 8.3%; with 1200 mg calcium per day, the mean absorption was 2.6% Ϯ 1.5%. Within this range, reduction of the calcium supply by 70 mg increased the oxalate absorption by 1% and vice versa. Calcium addition beyond 1200 mg/d reduced the oxalate absorption only one-tenth as effectively. With 1800 mg calcium per day, the mean absorption was 1.7% Ϯ 0.9%. The findings may explain why a low-calcium diet increases the risk of calcium oxalate stone formation.For decades, a mainstay in the treatment of patients with calcium (Ca) urinary stones has been a Ca-restricted diet (1). Reduction of the Ca content of the diet reliably reduced the amount of Ca excreted in urine. This reduction was believedbut never proven-to reduce the risk of Ca stone formation. By contrast, already in 1969, a Ca-restricted diet was shown to increase the gastrointestinal absorption of oxalate (2), leading to increased amounts of oxalate in the urine and an increased risk of the formation of Ca oxalate stones. Therefore, to reduce oxalate absorption and the resulting risk of formation of Ca oxalate stones, high-Ca supplements were routinely prescribed to obese patients after ileal bypass surgery (3). The reason why these contradictory and confusing recommendations persisted for so long is the lack of prospective studies and the fact that analysis of oxalate remained unreliable (4) until the mid-1980s. Consequently, the amount of dietary oxalate excreted in urine and its role for renal stone formation were underestimated (5). The fact that a low-Ca diet emerged as a risk factor for Ca oxalate calculi and that a high-Ca diet emerged as a protective factor in two large epidemiologic studies (6,7) is still frequently ignored. Hence, the advice to restrict Ca may still be given to patients with recurrent Ca oxalate urinary stones.We wanted to clear up the confusion generated by the contradictory results as well as the contradictory recommendations, and to answer the following question: To what extent does Ca intake influence the gastrointestinal oxalate absorption? Therefore, we quantitatively measured the dependence of oxalate absorption on Ca intake. The physiologic daily dietary Ca intake lies between approximately 370 and 1200 mg. Intakes of less than 300 mg Ca never occur in adults except in those who reduce food intake to lose weight. ...

show abstract

Contribution of dietary oxalate to urinary oxalate excretion

Cited by 427 publications

References 22 publications

Oxalate Intake and the Risk for Nephrolithiasis

Oxalate Intake and the Risk for Nephrolithiasis

Intestinal and renal handling of oxalate loads in normal individuals and stone formers

Dependence of Oxalate Absorption on the Daily Calcium Intake

Contact Info

Product

Resources

About