title: Association of urinary sodium-to-potassium ratio with obesity in a multiethnic cohort.
abstract: BACKGROUND
  Previous studies that reported an association of dietary Na(+) intake with metabolic syndrome were limited by the use of imprecise measures of obesity, Na(+) intake, or exclusion of multiethnic populations. The effect of dietary K(+) intake on obesity is less well described.
  
  
  OBJECTIVE
  We hypothesized that high dietary Na(+) and low K(+), based on the ratio of urinary Na(+) to K(+) (U[Na(+)]/[K(+)]) in a first-void morning urinary sample, is independently associated with total body fat.
  
  
  METHODS
  In a prospective population-based cohort, 2782 participants in the community-dwelling, probability-sampled, multiethnic Dallas Heart Study were analyzed. The primary outcome established a priori was total-body percentage fat (TBPF) measured by dual-energy X-ray absorptiometry. The main predictor was U[Na(+)]/[K(+)]. Robust linear regression was used to explore an independent association between U[Na(+)]/[K(+)] and TBPF. The analyses were stratified by sex and race after their effect modifications were analyzed.
  
  
  RESULTS
  Of the cohort, 55.4% were female, 49.8% African American, 30.8% white, 17.2% Hispanic, and 2.2% other races. The mean (±SD) age was 44 ± 10 y, BMI (in kg/m(2)) was 30 ± 7, TBPF was 32 ± 10%, and U[Na(+)]/[K(+)] was 4.2 ± 2.6; 12% had diabetes. In the unadjusted and adjusted models, TBPF increased by 0.75 (95% CI: 0.25, 1.25) and 0.43 (0.15, 0.72), respectively (P = 0.003 for both), for every 3-unit increase in U[Na(+)]/[K(+)]. A statistically significant interaction was found between race and U[Na(+)] /[K(+)], so that the non-African American races had a higher TBPF than did the African Americans per unit increase in U[Na(+)]/[K(+)] (P-interaction < 0.0001 for both). No interaction was found between sex and U[Na(+)]/[K(+)].
  
  
  CONCLUSIONS
  The ratio of dietary Na(+) to K(+) intake may be independently associated with TBPF, and this association may be more pronounced in non-African Americans. Future studies should explore whether easily measured spot U[Na(+)]/[K(+)] can be used to monitor dietary patterns and guide strategies for obesity management.
authors.affiliation: Division of Nephrology, Department of Internal Medicine, Veterans Affairs North Texas Health Care System, Dallas, TX (NJ, EFE, and SSH); the Division of Nephrology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX (NJ, EFE, and SSH); the Division of Biostatistics, Department of Clinical Sciences, University of Texas Southwestern Medical Center, Dallas, TX (ATM); the Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX (IJN); and the Department of Clinical Nutrition and Center for Human Nutrition, University of Texas Southwestern Medical Center, Dallas, TX (GLV).
authors.forename: Nishank
authors.initials: N
authors.lastname: Jain
authors.forename: Abu T
authors.initials: AT
authors.lastname: Minhajuddin
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Neeland
authors.forename: Essam F
authors.initials: EF
authors.lastname: Elsayed
authors.forename: Gloria L
authors.initials: GL
authors.lastname: Vega
authors.forename: S Susan
authors.initials: SS
authors.lastname: Hedayati
mesh_terms: D050154:Adiposity; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure; D015992:Body Mass Index; D005006:Ethnicity; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D009765:Obesity / Q000208:ethnology* / Q000652:urine*; D017419:Potassium, Dietary / Q000032:analysis / Q000652:urine*; D011446:Prospective Studies; D012737:Sex Factors; D012982:Sodium, Dietary / Q000032:analysis / Q000652:urine*; D014280:Triglycerides / Q000097:blood
chemical_list: D001786:Blood Glucose; D017419:Potassium, Dietary; D012982:Sodium, Dietary; D014280:Triglycerides