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Body size and 24-hour urine composition.

Abstract

BACKGROUND

Greater body mass index (BMI) is a risk factor for kidney stones. However, the relation between BMI and the urinary excretion of many lithogenic factors remains unclear.

METHODS

We studied urine pH, urine volume, and 24-hour urinary excretion of calcium, oxalate, citrate, uric acid, sodium, magnesium, potassium, phosphate, and creatinine in stone-forming and non-stone-forming participants in the Health Professionals Follow-Up Study (599 stone-forming and 404 non-stone-forming men), Nurses' Health Study (888 stone-forming and 398 non-stone-forming older women), and Nurses' Health Study II (689 stone-forming and 295 non-stone-forming younger women). Each cohort was divided into quintiles of BMI. Tests of linear trend were conducted by 1-way analysis of variance. Linear regression models were adjusted for age, history of stone disease, dietary intake, and urinary factors.

RESULTS

Participants with greater BMIs excreted more urinary oxalate (P for trend <or= 0.04), uric acid (P < 0.001), sodium (P < 0.001), and phosphate (P < 0.001) than participants with lower BMIs. There was an inverse relation between BMI and urine pH (P <or= 0.02). Positive associations between BMI and urinary calcium excretion in men and stone-forming younger women (P <or= 0.02) did not persist after adjustment for urinary sodium and phosphate excretion. Because of differences in urinary volume and excretion of inhibitors such as citrate, we observed no relation between BMI and urinary supersaturation of calcium oxalate. Urinary supersaturation of uric acid increased with BMI (P <or= 0.01).

CONCLUSION

Positive associations between BMI and urinary calcium excretion likely are due to differences in animal protein and sodium intake. The greater incidence of kidney stones in the obese may be due to an increase in uric acid nephrolithiasis.

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  • Authors+Show Affiliations

    ,

    Renal Division and Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA. entaylor@partners.org

    Source

    MeSH

    Adult
    Body Mass Index
    Calcium
    Calcium Oxalate
    Citrates
    Comorbidity
    Creatinine
    Diabetes Mellitus
    Female
    Humans
    Hydrogen-Ion Concentration
    Hypertension
    Kidney Calculi
    Linear Models
    Magnesium
    Middle Aged
    Obesity
    Oxalates
    Phosphates
    Potassium
    Risk Factors
    Sodium
    Urine

    Pub Type(s)

    Journal Article
    Research Support, N.I.H., Extramural

    Language

    eng

    PubMed ID

    17162145

    Citation

    Taylor, Eric N., and Gary C. Curhan. "Body Size and 24-hour Urine Composition." American Journal of Kidney Diseases : the Official Journal of the National Kidney Foundation, vol. 48, no. 6, 2006, pp. 905-15.
    Taylor EN, Curhan GC. Body size and 24-hour urine composition. Am J Kidney Dis. 2006;48(6):905-15.
    Taylor, E. N., & Curhan, G. C. (2006). Body size and 24-hour urine composition. American Journal of Kidney Diseases : the Official Journal of the National Kidney Foundation, 48(6), pp. 905-15.
    Taylor EN, Curhan GC. Body Size and 24-hour Urine Composition. Am J Kidney Dis. 2006;48(6):905-15. PubMed PMID: 17162145.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Body size and 24-hour urine composition. AU - Taylor,Eric N, AU - Curhan,Gary C, PY - 2006/07/10/received PY - 2006/09/11/accepted PY - 2006/12/13/pubmed PY - 2007/1/11/medline PY - 2006/12/13/entrez SP - 905 EP - 15 JF - American journal of kidney diseases : the official journal of the National Kidney Foundation JO - Am. J. Kidney Dis. VL - 48 IS - 6 N2 - BACKGROUND: Greater body mass index (BMI) is a risk factor for kidney stones. However, the relation between BMI and the urinary excretion of many lithogenic factors remains unclear. METHODS: We studied urine pH, urine volume, and 24-hour urinary excretion of calcium, oxalate, citrate, uric acid, sodium, magnesium, potassium, phosphate, and creatinine in stone-forming and non-stone-forming participants in the Health Professionals Follow-Up Study (599 stone-forming and 404 non-stone-forming men), Nurses' Health Study (888 stone-forming and 398 non-stone-forming older women), and Nurses' Health Study II (689 stone-forming and 295 non-stone-forming younger women). Each cohort was divided into quintiles of BMI. Tests of linear trend were conducted by 1-way analysis of variance. Linear regression models were adjusted for age, history of stone disease, dietary intake, and urinary factors. RESULTS: Participants with greater BMIs excreted more urinary oxalate (P for trend <or= 0.04), uric acid (P < 0.001), sodium (P < 0.001), and phosphate (P < 0.001) than participants with lower BMIs. There was an inverse relation between BMI and urine pH (P <or= 0.02). Positive associations between BMI and urinary calcium excretion in men and stone-forming younger women (P <or= 0.02) did not persist after adjustment for urinary sodium and phosphate excretion. Because of differences in urinary volume and excretion of inhibitors such as citrate, we observed no relation between BMI and urinary supersaturation of calcium oxalate. Urinary supersaturation of uric acid increased with BMI (P <or= 0.01). CONCLUSION: Positive associations between BMI and urinary calcium excretion likely are due to differences in animal protein and sodium intake. The greater incidence of kidney stones in the obese may be due to an increase in uric acid nephrolithiasis. SN - 1523-6838 UR - https://www.unboundmedicine.com/medline/citation/17162145/Body_size_and_24_hour_urine_composition_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0272-6386(06)01439-9 DB - PRIME DP - Unbound Medicine ER -