A Prospective Study of Prepregnancy Dietary Iron Intake and Risk for Gestational Diabetes Mellitus

Diabetes Care
Q1
Jun 2011
Citations:126
Influential Citations:7
Observational Studies (Human)
83
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Methods
Prospective cohort study (Nurses' Health Study II). 13,475 women with a singleton pregnancy between 1991 and 2001; female U.S. registered nurses; exclusions included multiple gestations, implausible energy intake, preexisting diabetes, GDM, cancer, cardiovascular disease, peri-menopausal status, or missing data. GDM cases identified by self-report on biennial questionnaires and validated against medical records. Dietary iron intake assessed with a 133-item semiquantitative FFQ every 4 years; cumulative average intakes of total iron, heme iron, nonheme iron, and iron supplements used in analyses.
Results
Higher prepregnancy dietary heme iron intake is positively associated with GDM risk. In multivariate models, extreme quintiles of heme iron intake yielded RRs of 2.13 (1.70–2.67) age-adjusted and 1.58 (1.21–2.08) fully adjusted (P for trend = 0.0001). Every 0.5 mg/day increase in heme iron intake was associated with RR 1.22 (1.10–1.36). No significant associations were found for total dietary iron, nonheme iron, or supplemental iron with GDM risk. Adjusting for red meat components attenuated the association; after additional adjustment for red meat, the RR for the highest quintile was 1.29 (0.95–1.75). Findings suggest that greater prepregnancy heme iron intake may increase GDM risk; reducing prepregnancy heme iron intake could potentially lower risk. Results point to iron-associated oxidative stress as a potential mechanism; confirmation with measures of body iron stores is warranted.
Limitations
Observational design with potential residual confounding; dietary assessment via FFQ subject to measurement error; GDM ascertainment based on self-report (though validated); dietary data during pregnancy not measured; cohort primarily white, educated nurses, limiting generalizability.

Abstract

OBJECTIVE It is important to identify modifiable factors that may lower gestational diabetes mellitus (GDM) risk. Dietary iron is of particular interest given that iron is a strong prooxidant, and high body iron levels can damage pancreatic β-cell fu...