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The influence of a high-oxalate/low-calcium diet on calcium oxalate renal stone risk factors in non-stone-forming black and white South African subjects.

Abstract

OBJECTIVE

To evaluate the influence of a high-oxalate/low-calcium diet on calcium oxalate stone risk factors in both black South Africans (who are largely immune to kidney stones) and white South Africans (in whom stones are more common).

SUBJECTS AND METHODS

Urinary and dietary variables were examined in 11 black and 11 white South African men. None of the subjects had had a kidney stone or any metabolic illness. Their normal domestic food intake was assessed using a semiquantitative food frequency questionnaire. Subjects were given a standardized high-oxalate/low-calcium diet for 3 days; 24-h urine samples were collected before the protocol and during the final day. The samples were analysed using routine modern laboratory techniques. The urine analysis data were used to calculate the Tiselius risk index and the relative urinary supersaturations of calcium oxalate, uric acid and calcium phosphate.

RESULTS

Urine analysis showed an intriguing anomaly; black subjects had significantly higher urinary pH and oxalate values than whites (6.50 vs 6.21 and 0.23 vs 0.14 mmol/24 h, respectively), while their urinary citrate was lower (1.47 vs 3.69 mmol/24 h). In addition, the Tiselius risk index and relative supersaturation of calcium oxalate were higher in black subjects. These results are contrary to those which might have been reasonably expected when comparing stone-free and stone-prone groups. After the dietary protocol, the only urinary variable which changed significantly was urinary oxalate, which increased by 57% in whites.

CONCLUSION

Factors which are conventionally used to assess stone risk (pH, oxaluria, citraturia, relative supersaturation) are not helpful in identifying why South African blacks are relatively immune to stones. We suggest that relatively lower oxalate absorption rates may be a physiological feature of this racial group.

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  • Authors+Show Affiliations

    ,

    Department of Chemistry, and Nutrition and Dietetics Unit, University of Cape Town, Cape Town, South Africa.

    ,

    Source

    BJU international 87:4 2001 Mar pg 307-11

    MeSH

    African Americans
    African Continental Ancestry Group
    Calcium Oxalate
    Calcium, Dietary
    Diet
    European Continental Ancestry Group
    Humans
    Hydrogen-Ion Concentration
    Kidney Calculi
    Male
    Risk Factors
    South Africa

    Pub Type(s)

    Journal Article

    Language

    eng

    PubMed ID

    11251520

    Citation

    Lewandowski, S, et al. "The Influence of a High-oxalate/low-calcium Diet On Calcium Oxalate Renal Stone Risk Factors in Non-stone-forming Black and White South African Subjects." BJU International, vol. 87, no. 4, 2001, pp. 307-11.
    Lewandowski S, Rodgers A, Schloss I. The influence of a high-oxalate/low-calcium diet on calcium oxalate renal stone risk factors in non-stone-forming black and white South African subjects. BJU Int. 2001;87(4):307-11.
    Lewandowski, S., Rodgers, A., & Schloss, I. (2001). The influence of a high-oxalate/low-calcium diet on calcium oxalate renal stone risk factors in non-stone-forming black and white South African subjects. BJU International, 87(4), pp. 307-11.
    Lewandowski S, Rodgers A, Schloss I. The Influence of a High-oxalate/low-calcium Diet On Calcium Oxalate Renal Stone Risk Factors in Non-stone-forming Black and White South African Subjects. BJU Int. 2001;87(4):307-11. PubMed PMID: 11251520.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - The influence of a high-oxalate/low-calcium diet on calcium oxalate renal stone risk factors in non-stone-forming black and white South African subjects. AU - Lewandowski,S, AU - Rodgers,A, AU - Schloss,I, PY - 2001/3/17/pubmed PY - 2001/5/1/medline PY - 2001/3/17/entrez SP - 307 EP - 11 JF - BJU international JO - BJU Int. VL - 87 IS - 4 N2 - OBJECTIVE: To evaluate the influence of a high-oxalate/low-calcium diet on calcium oxalate stone risk factors in both black South Africans (who are largely immune to kidney stones) and white South Africans (in whom stones are more common). SUBJECTS AND METHODS: Urinary and dietary variables were examined in 11 black and 11 white South African men. None of the subjects had had a kidney stone or any metabolic illness. Their normal domestic food intake was assessed using a semiquantitative food frequency questionnaire. Subjects were given a standardized high-oxalate/low-calcium diet for 3 days; 24-h urine samples were collected before the protocol and during the final day. The samples were analysed using routine modern laboratory techniques. The urine analysis data were used to calculate the Tiselius risk index and the relative urinary supersaturations of calcium oxalate, uric acid and calcium phosphate. RESULTS: Urine analysis showed an intriguing anomaly; black subjects had significantly higher urinary pH and oxalate values than whites (6.50 vs 6.21 and 0.23 vs 0.14 mmol/24 h, respectively), while their urinary citrate was lower (1.47 vs 3.69 mmol/24 h). In addition, the Tiselius risk index and relative supersaturation of calcium oxalate were higher in black subjects. These results are contrary to those which might have been reasonably expected when comparing stone-free and stone-prone groups. After the dietary protocol, the only urinary variable which changed significantly was urinary oxalate, which increased by 57% in whites. CONCLUSION: Factors which are conventionally used to assess stone risk (pH, oxaluria, citraturia, relative supersaturation) are not helpful in identifying why South African blacks are relatively immune to stones. We suggest that relatively lower oxalate absorption rates may be a physiological feature of this racial group. SN - 1464-4096 UR - https://www.unboundmedicine.com/medline/citation/11251520/The_influence_of_a_high_oxalate/low_calcium_diet_on_calcium_oxalate_renal_stone_risk_factors_in_non_stone_forming_black_and_white_South_African_subjects_ L2 - https://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=1464-4096&date=2001&volume=87&issue=4&spage=307 DB - PRIME DP - Unbound Medicine ER -