Scientific Publications
The absorption of iron from whole diets: a systematic review
American Journal of Clinical Nutrition, 98, 65-81
Background: Absorption factors are required to convert physiological requirements for iron into dietary reference values, but absorption from single meals cannot be used to estimate dietary iron absorption. Objectives: To undertake a systematic review on iron absorption from whole diets. Design: A structured search was completed using MEDLINE, EMBASE and Cochrane CENTRAL databases from inception to November 2011. Formal inclusion/exclusion criteria were applied, and data extraction, validity assessment and meta-analyses undertaken. Results: Nineteen studies from the US, Europe and Mexico were included. Absorption from diets was higher with an enhancer (Standard Mean Difference (SMD) 0.53; 95%CI 0.21 to 0.85; P=0.001), also high versus low bioavailability diets (SMD 0.96; 95%CI 0.51 to 1.41; P<0.0001) but single inhibitors did not reduce absorption (possibly due to the limited number of studies/participants and their heterogeneity). A regression equation to calculate iron absorption was derived by pooling data for iron status (serum/plasma ferritin) and dietary enhancers/inhibitors from 58 individuals (all from U.S. studies): log[non-heme iron absorption, %] = -0.73 log[ferritin, µg/L] +0.11 [modifier] + 1.82). In individuals with serum ferritin concentrations from 6-80 µg/L, predicted absorption ranged from 2.1-23.0%. Conclusions: There were large variations in mean non-heme iron absorption (0.7-22.9%) between studies, which depended on iron status (diet had greater impact at low serum/plasma ferritin) and dietary enhancers/inhibitors. Iron absorption was predicted from serum ferritin concentration and dietary modifiers using a regression equation. Extrapolation of these findings to developing countries and to men and women of different ages will require further high quality, controlled trials.
American Journal of Clinical Nutrition, 98, 65-81
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