Total Iron Bioavailability from the US Diet Is Lower Than the Current Estimate

Area of Science:

• Nutritional Science
• Human Physiology
• Dietary Assessment

Background:

• Previous estimates of total iron bioavailability from the US diet were based on limited data.
• Newer data suggest a potential need to re-evaluate the established 18% bioavailability figure.

Purpose of the Study:

• To estimate total iron bioavailability from the US diet using a novel algorithm for nonheme iron absorption and a conservative heme iron absorption value.
• To provide updated data for assessing current iron bioavailability estimates.

Main Methods:

• Utilized data from NHANES 2001-2002, including dietary intake and biomarkers.
• Employed a recently developed algorithm to estimate nonheme iron absorption and incorporated a conservative estimate for heme iron absorption.
• Applied statistical methods accounting for survey design complexities to calculate means and confidence intervals.

Main Results:

• Estimated total iron absorption was 15.5% or 15.1%, depending on the calculation approach.
• Unadjusted nonheme iron absorption varied significantly by sex and race/ethnicity.
• Nonheme iron absorption was higher in females than males and higher in Mexican Americans and non-Hispanic blacks compared to non-Hispanic whites.

Conclusions:

• The study provides updated figures for iron bioavailability from the US diet.
• These findings suggest the previously accepted 18% estimate may be an overestimation.
• The data are valuable for refining dietary recommendations and public health assessments related to iron intake.