title: Ethnic differences in urinary calcium and phosphate excretion between Gambian and British older adults.
abstract: Ethnic differences in renal calcium and phosphate excretion exist, which may depend on differences in their dietary intakes and regulatory factors. We report highly significant differences in urinary calcium and phosphate excretion between white British and Gambian adults after statistical adjustment for mineral intakes, indicating an independent effect of ethnicity.
  
  
  BACKGROUND
  Populations vary in their risk of age-related osteoporosis. There are racial or ethnic differences in the metabolism of the bone-forming minerals calcium (Ca) and phosphate (P), with a lower renal Ca and P excretion in African-Americans compared to white counterparts, even at similar intakes and rates of absorption. Also, Africans in The Gambia have a lower Ca excretion compared to white British subjects, groups known to differ in their dietary Ca intake. Here, we report on differences in urinary Ca and P excretion between Gambian and white British adults while allowing for known predictors, including dietary intakes.
  
  
  METHODS
  Participants were healthy white British (n = 60) and Gambian (n = 61) men and women aged 60-75 years. Fasting blood and 2-h urine samples were collected. Markers of Ca and P metabolism were analysed. Dietary intake was assessed with country-specific methods.
  
  
  RESULTS
  White British older adults had higher creatinine-corrected urinary Ca and P excretion (uCa/uCr, uP/uCr) and lower tubular maximum of Ca and P compared to Gambian counterparts. The predictors of urinary Ca and P differed between groups. Multiple regression analysis showed that dietary Ca and Ca/P were predictors of uCa/uCr and uP/uCr, respectively. Ethnicity remained a significant predictor of uCa/uCr and uP/uCr after adjustment for diet and other factors.
  
  
  CONCLUSIONS
  Gambian older adults have higher renal Ca conservation than British counterparts. Dietary mineral intakes were predictors of the differences in urinary Ca and P excretion, but ethnicity remained a highly significant predictor after statistical adjustment. This suggests that ethnicity has an independent effect on renal Ca and P handling.
authors.affiliation: Medical Research Council Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, CB1 9NL, UK.
authors.forename: J
authors.initials: J
authors.lastname: Redmond
authors.forename: L
authors.initials: L
authors.lastname: Palla
authors.forename: L
authors.initials: L
authors.lastname: Yan
authors.forename: L M A
authors.initials: LM
authors.lastname: Jarjou
authors.forename: A
authors.initials: A
authors.lastname: Prentice
authors.forename: I
authors.initials: I
authors.lastname: Schoenmakers
mesh_terms: D000368:Aged; D002118:Calcium / Q000652:urine*; D003430:Cross-Sectional Studies; D004032:Diet / Q000208:ethnology*; D005260:Female; D005502:Food; D005714:Gambia / Q000208:ethnology; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010710:Phosphates / Q000652:urine*; D012307:Risk Factors; D006113:United Kingdom / Q000208:ethnology
chemical_list: D010710:Phosphates; D002118:Calcium