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Effects of 5 different diets on urinary risk factors for calcium oxalate kidney stone formation: evidence of different renal handling mechanisms in different race groups.

Abstract

PURPOSE

Since the incidence of renal calculi in the South African black population is extremely rare while in white subjects it occurs at the same rate as elsewhere in the western world, we investigated the possibility that different renal handling mechanisms in response to different dietary challenges might occur in the 2 race groups.

MATERIALS AND METHODS

We administered 5 different dietary protocols, including low calcium, high oxalate, vitamin C, high salt and lacto-vegetarian, to 10 healthy male subjects from each race group. We collected 24-hour urine at baseline and after 4 days on the prescribed diet which were analyzed for biochemical and physicochemical risk factors. Dietary intake was controlled throughout the experimental period. A 24-hour dietary recall questionnaire was recorded at baseline and analyzed using food composition tables. Statistical analysis of variance was performed on all the data.

RESULTS

The low calcium diet caused statistically significant changes only in black subjects, which consisted of urinary oxalate increase (0.17 to 0.23 mmol./24 hours, p = 0.01), relative supersaturation of calcium oxalate decrease (1.88 to 0.97, p = 0.03) and relative supersaturation of brushite increase (0.85 to 1.69, p = 0.03). The high oxalate diet caused statistically significant changes in both race groups but these changes were different in the 2 groups. In white subjects urinary pH increased (6.24 to 6.62, p = 0.01), potassium excretion increased (40.01 to 73.49, p = 0.01) and relative supersaturation of brushite increased (1.34 to 2.12, p = 0.05). In black subjects urinary citrate increased (1.94 to 2.99 mmol./24 hours, p = 0.01). Clinically unimportant changes occurred in both race groups after the other 3 diets.

CONCLUSIONS

Renal handling of dietary calcium and oxalate in South African black and white subjects is different and may explain the different stone incidence in the 2 race groups.

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  • Publisher Full Text
  • Authors+Show Affiliations

    ,

    Department of Chemistry, University of Cape Town, South Africa.

    Source

    The Journal of urology 168:3 2002 Sep pg 931-6

    MeSH

    Adolescent
    Adult
    African Continental Ancestry Group
    Ascorbic Acid
    Calcium Oxalate
    Calcium, Dietary
    Continental Population Groups
    Diet
    Diet, Vegetarian
    European Continental Ancestry Group
    Humans
    Kidney
    Kidney Calculi
    Male
    Oxalates
    Risk Factors
    Sodium, Dietary

    Pub Type(s)

    Comparative Study
    Journal Article
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    12187193

    Citation

    Rodgers, Allen L., and Sonja Lewandowski. "Effects of 5 Different Diets On Urinary Risk Factors for Calcium Oxalate Kidney Stone Formation: Evidence of Different Renal Handling Mechanisms in Different Race Groups." The Journal of Urology, vol. 168, no. 3, 2002, pp. 931-6.
    Rodgers AL, Lewandowski S. Effects of 5 different diets on urinary risk factors for calcium oxalate kidney stone formation: evidence of different renal handling mechanisms in different race groups. J Urol. 2002;168(3):931-6.
    Rodgers, A. L., & Lewandowski, S. (2002). Effects of 5 different diets on urinary risk factors for calcium oxalate kidney stone formation: evidence of different renal handling mechanisms in different race groups. The Journal of Urology, 168(3), pp. 931-6.
    Rodgers AL, Lewandowski S. Effects of 5 Different Diets On Urinary Risk Factors for Calcium Oxalate Kidney Stone Formation: Evidence of Different Renal Handling Mechanisms in Different Race Groups. J Urol. 2002;168(3):931-6. PubMed PMID: 12187193.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Effects of 5 different diets on urinary risk factors for calcium oxalate kidney stone formation: evidence of different renal handling mechanisms in different race groups. AU - Rodgers,Allen L, AU - Lewandowski,Sonja, PY - 2002/8/21/pubmed PY - 2002/9/19/medline PY - 2002/8/21/entrez SP - 931 EP - 6 JF - The Journal of urology JO - J. Urol. VL - 168 IS - 3 N2 - PURPOSE: Since the incidence of renal calculi in the South African black population is extremely rare while in white subjects it occurs at the same rate as elsewhere in the western world, we investigated the possibility that different renal handling mechanisms in response to different dietary challenges might occur in the 2 race groups. MATERIALS AND METHODS: We administered 5 different dietary protocols, including low calcium, high oxalate, vitamin C, high salt and lacto-vegetarian, to 10 healthy male subjects from each race group. We collected 24-hour urine at baseline and after 4 days on the prescribed diet which were analyzed for biochemical and physicochemical risk factors. Dietary intake was controlled throughout the experimental period. A 24-hour dietary recall questionnaire was recorded at baseline and analyzed using food composition tables. Statistical analysis of variance was performed on all the data. RESULTS: The low calcium diet caused statistically significant changes only in black subjects, which consisted of urinary oxalate increase (0.17 to 0.23 mmol./24 hours, p = 0.01), relative supersaturation of calcium oxalate decrease (1.88 to 0.97, p = 0.03) and relative supersaturation of brushite increase (0.85 to 1.69, p = 0.03). The high oxalate diet caused statistically significant changes in both race groups but these changes were different in the 2 groups. In white subjects urinary pH increased (6.24 to 6.62, p = 0.01), potassium excretion increased (40.01 to 73.49, p = 0.01) and relative supersaturation of brushite increased (1.34 to 2.12, p = 0.05). In black subjects urinary citrate increased (1.94 to 2.99 mmol./24 hours, p = 0.01). Clinically unimportant changes occurred in both race groups after the other 3 diets. CONCLUSIONS: Renal handling of dietary calcium and oxalate in South African black and white subjects is different and may explain the different stone incidence in the 2 race groups. SN - 0022-5347 UR - https://www.unboundmedicine.com/medline/citation/12187193/Effects_of_5_different_diets_on_urinary_risk_factors_for_calcium_oxalate_kidney_stone_formation:_evidence_of_different_renal_handling_mechanisms_in_different_race_groups_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0022-5347(05)64545-4 DB - PRIME DP - Unbound Medicine ER -