Dietary intake of heme iron and body iron status are associated with the risk of gestational diabetes mellitus: a systematic review and meta-analysis

Background and Objectives: Some potential role of iron overload in the development of diabetes mellitus have been suggested. Our study aimed to systematically assess the association between the risk of gestational diabetes mellitus (GDM) and iron intakes/body iron status. Methods and Study Design: PubMed and Web of Science were searched for relevant articles. Relative risks (RR) of GDM in relation to dietary iron intakes and body iron stores were pooled with the random-effects model. Weighted mean differences of iron blood markers between GDM and non-GDM individuals were also analyzed. Results: Twenty-five studies were included in the qualitative analysis, and 23 studies with 29,378 participants and 3,034 GDM patients were included in the quantitative analysis. Dietary intake of heme iron was significantly associated with GDM risk (RR=1.65, 95% CI: 1.28 to 2.12), and the pooled RR for each 1mg/day increment of heme iron intake was 1.38 (95% CI: 1.19 to 1.61). No association between GDM and the intakes of nonheme iron, total iron, or supplemental iron was detected. Body iron stores, as represented by serum ferritin level, were correlated with GDM risk (RR=1.64, 95% CI: 1.27 to 2.11). Moreover, the concentrations of both serum ferritin and serum iron were increased in GDM patients, compared with non-GDM individuals. Conclusions: Increased dietary intake of heme iron and body iron status are positively associated with the risk of GDM development in pregnant women. Future studies are warranted to better understand the role of iron in GDM development.