title: Total Iron Bioavailability from the US Diet Is Lower Than the Current Estimate.
abstract: BACKGROUND
  Total (heme and nonheme) iron bioavailability from the US diet has been estimated to be 18% based on a single human absorption study. New data, however, suggest that it may be time to revisit this estimate.
  
  
  OBJECTIVE
  We estimated total iron bioavailability from the US diet with the use of our recently reported algorithm that estimates nonheme iron absorption and a conservative value for heme iron absorption.
  
  
  METHODS
  We used dietary intake and biomarker information from the NHANES 2001-2002, MyPyramid Equivalents Database, and Food and Nutrient Database for Dietary Studies. The survey package in R software was used to estimate means and CIs, taking into account the strata, primary sampling units, and appropriate survey weight. We implemented 2 different approaches to estimate total iron absorption. In the first approach, we included all survey participants but adjusted the geometric mean of nonheme iron absorption to 15 μg ferritin/L serum to mimic values of individuals with no iron stores; in the second approach, absorption was estimated for only nonanemic subjects with no iron stores. A total sample size of 6631 was used based on availability of dietary and iron status biomarker data and C-reactive protein concentration ≤ 6 mg/L.
  
  
  RESULTS
  The geometric mean (95% CI) of unadjusted nonheme iron absorption for all subjects was 3.7% (3.6%, 3.8%), higher in female subjects [5.6% (5.4%, 5.7%)] than male subjects [2.6% (2.5%, 2.7%)] (P < 0.0001). Nonheme iron absorption was lower in non-Hispanic whites [3.5% (3.4%, 3.6%)] than Mexican Americans [4.5% (4.2%, 4.8%)] and non-Hispanic blacks [4.4% (4.1%, 4.7%)]. Estimated total iron absorption was 15.5% or 15.1%, depending on which approach was used to carry out the calculations.
  
  
  CONCLUSIONS
  This study provides useful data for evaluating the current value of iron bioavailability from the US diet.
authors.affiliation: Department of Food Science and Human Nutrition and.
authors.forename: Seth M
authors.identifier: http://orcid.org/0000-0003-3860-0522
authors.initials: SM
authors.lastname: Armah
authors.affiliation: Department of Statistics, Iowa State University, Ames, IA.
authors.forename: Alicia L
authors.initials: AL
authors.lastname: Carriquiry
authors.affiliation: Department of Food Science and Human Nutrition and mbreddy@iastate.edu.
authors.forename: Manju B
authors.initials: MB
authors.lastname: Reddy
mesh_terms: D000293:Adolescent; D000328:Adult; D001205:Ascorbic Acid / Q000008:administration & dosage / Q000097:blood; D001682:Biological Availability; D002097:C-Reactive Protein / Q000378:metabolism; D002136:Calcium, Dietary / Q000008:administration & dosage / Q000097:blood; D002648:Child; D002675:Child, Preschool; D004032:Diet; D002149:Energy Intake; D005260:Female; D005293:Ferritins / Q000097:blood; D006801:Humans; D007408:Intestinal Absorption; D019266:Iron, Dietary / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D010833:Phytic Acid / Q000008:administration & dosage / Q000097:blood; D059808:Polyphenols / Q000008:administration & dosage; D064167:Recommended Dietary Allowances; D013662:Tea / Q000737:chemistry; D014481:United States; D055815:Young Adult
chemical_list: D002136:Calcium, Dietary; D019266:Iron, Dietary; D059808:Polyphenols; D013662:Tea; D010833:Phytic Acid; D002097:C-Reactive Protein; D005293:Ferritins; D001205:Ascorbic Acid
keywords: US diet; bioavailability; ethnicity; gender; nonheme iron