title: Nonheme-iron absorption in first-degree relatives is highly correlated: a stable-isotope study in mother-child pairs.
abstract: BACKGROUND
  Iron absorption in humans is highly variable even after iron status and dietary components that influence iron absorption are controlled for. Inherited factors may help explain this variance.
  
  
  OBJECTIVE
  Our objective was to compare nonheme-iron absorption from a noninhibitory, stable-isotope-labeled test meal in preschool-aged children and their mothers.
  
  
  METHODS
  We provided 72 test meals based on degermed maize flour and milk powder and fortified with [(57)Fe]ferrous fumarate or [(58)Fe]ferrous sulfate to healthy Mexican preschool children [n = 18; mean (+/-SD) age: 3.6 +/- 1.0 y] and their mothers [n = 18; mean (+/-SD) age: 28.0 +/- 5.2 y]. Iron absorption was calculated on the basis of incorporation of isotopes into erythrocytes after 14 d and was adjusted for differences in iron status.
  
  
  RESULTS
  There was a wide variation in iron absorption from the test meals: in the mothers and children, the median fractional absorption of ferrous sulfate was 22.55% (range: 1.65-54.83%) and 5.51% (range: 2.23-17.20%), respectively (P < 0.0001). After adjustment for serum ferritin, the significant difference in absorption between mothers and their children disappeared. Despite this broad range of iron absorption, corrected fractional iron absorption from the ferrous fumarate-fortified (r(2) = 0.582) and the ferrous sulfate-fortified test meals (r(2) = 0.557) was strongly correlated in mothers and their children (P < 0.0001). There was a striking positive correlation between the mean corrected fractional iron absorption from both test meals in mothers and their children (r(2) = 0.782, P < 0.0001). In regression analyses that included age, sex, and hemoglobin, the only significant predictor of corrected fractional iron absorption in children was corrected fractional iron absorption in their mothers (standardized beta = 0.884, P < 0.001).
  
  
  CONCLUSIONS
  Nonheme-iron absorption exhibits a strong familial tendency. After differences in meal matrix and serum ferritin are accounted for, these data suggest that inheritance and/or shared environmental factors explain most of the variance in dietary iron absorption.
authors.affiliation: Swiss Federal Institute of Technology, Zurich, Switzerland. michael.zimmermann@ilw.agrl.ethz.ch
authors.forename: Michael B
authors.initials: MB
authors.lastname: Zimmermann
authors.forename: Mary
authors.initials: M
authors.lastname: Harrington
authors.forename: Salvador
authors.initials: S
authors.lastname: Villalpando
authors.forename: Richard F
authors.initials: RF
authors.lastname: Hurrell
mesh_terms: D000328:Adult; D018798:Anemia, Iron-Deficiency / Q000097:blood / Q000235:genetics*; D000818:Animals; D002675:Child, Preschool; D004032:Diet; D004912:Erythrocytes / Q000378:metabolism; D005260:Female; D005293:Ferritins / Q000097:blood; D005296:Ferrous Compounds / Q000008:administration & dosage; D005527:Food, Fortified; D006801:Humans; D007408:Intestinal Absorption / Q000235:genetics*; D007501:Iron / Q000008:administration & dosage / Q000493:pharmacokinetics*; D007503:Iron Isotopes / Q000008:administration & dosage / Q000493:pharmacokinetics; D019266:Iron, Dietary / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008297:Male; D008800:Mexico; D008892:Milk; D009035:Mothers; D012016:Reference Values; D055815:Young Adult; D003313:Zea mays
chemical_list: D005296:Ferrous Compounds; D007503:Iron Isotopes; D019266:Iron, Dietary; C020748:ferrous sulfate; D005293:Ferritins; D007501:Iron; C031621:ferrous fumarate