Otherindependent cross-checkabstract checked I-VEG-118 standard review

Diet supplies a sizeable share of urine oxalate

Contribution of dietary oxalate to urinary oxalate excretion.

Overview

Holmes RP et al.. Kidney Int 2001 · PMID 11135080 · DOI 10.1046/j.1523-1755.2001.00488.x

In controlled diets, food supplied 24-42% of urinary oxalate, and more (53%) when calcium intake was low.

Does the study support the specific claim? Partly · Methodological quality: moderate

Study explained simply

What did the researchers want to find out?: Quantify dietary contribution to urinary oxalate.
How was the study done?: Controlled feeding.
How many people, animals or samples were studied?: Healthy adults (n not in abstract).
What was actually found?: Dietary share 24-53%.
How large was the observed effect?: See results.
What do the results mean in everyday life?: Eating calcium with oxalate-rich greens reduces oxalate absorption.
What are the study's limitations?: Small, physiological endpoint.
What does it say about Elawady's specific claim?: Mixed.
Do the results apply to Germany and Europe?: Universal.
What can explicitly not be concluded from this study?: Cannot show stone risk.

Authors: Holmes RP et al.
Journal: Kidney Int
Year: 2001
Identifier: PMID 11135080 DOI 10.1046/j.1523-1755.2001.00488.x
Verification: verified – PubMed efetch 2026-10-26; Crossref 2026-10-26
Retracted: no
Corrections: none
Extent checked: abstract only
Conflicts of interest and funding: Funding (PubMed grant list): NCRR NIH HHS; NIDDK NIH HHS

What fraction of urinary oxalate comes from dietary oxalate?

Study design: Other – Controlled feeding study with formula and solid-food diets of known oxalate content
Population: Healthy adults
Country: USA
Period: not stated in abstract
Sample size: not stated in abstract
Inclusion and exclusion criteria: not stated in abstract

Exposure / intervention: Diets with 10, 50, 250 mg oxalate/2,500 kcal; formula 0 and 180 mg; calcium 1,002 vs 391 mg
Comparator: Different oxalate/calcium levels
Endpoints: 24-h urinary oxalate
Statistical methods: Within-subject comparisons

Results: Urinary oxalate rose with dietary oxalate; dietary contribution 24.4% +/- 15.5% (10 mg diet) to 41.5% +/- 9.1% (250 mg diet). Lowering calcium from 1,002 to 391 mg on a 250 mg oxalate diet raised urinary oxalate by 28.2% and the dietary share to 52.6%.
Absolute risks: not reported
Authors' conclusion: Dietary oxalate contributes more to urinary oxalate than previously recognized; dietary calcium influences oxalate bioavailability.

Shares are means +/- SD; no outcome data.

Mixed: dietary oxalate matters physiologically, and calcium co-ingestion strongly modifies it.

Taylor 2008 (small effect in free-living people).

Universal.

Supports oxalate moderation and adequate calcium for stone formers; not evidence that greens cause stones in general.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	moderate
Risk of bias	some concerns
Precision of results	low
Directness	indirect
Reproducibility	partly replicated
Consistency with the overall evidence	mixed
Regional transferability	high
Adequacy of the interpretation (by the archive)	not applicable

Stone outcomes.