A new study reveals that consuming more heme iron—found in red meat and other animal products—may increase the risk of developing type 2 diabetes (T2D), contrary to non-heme iron, which is primarily found in plant foods. While previous studies have suggested a link between heme iron and T2D, this research provides clearer evidence and explanations.
“In contrast to earlier research that mainly used observational data, we combined various types of information, such as epidemiological data, traditional metabolic markers, and advanced metabolomics,” stated lead researcher Fenglei Wang, a research associate in the Department of Nutrition. “This approach gave us a more in-depth understanding of how iron intake relates to T2D risk and the possible metabolic pathways involved.”
The findings of this research will be published on August 13 in Nature Metabolism.
The researchers evaluated the connection between iron consumption and T2D through dietary reports spanning 36 years from 206,615 adults participating in the Nurses’ Health Studies I and II as well as the Health Professionals Follow-up Study. They analyzed participants’ consumption of different iron types—total iron, heme iron, non-heme iron, dietary iron (from food), and supplemental iron (from supplements)—while considering various health and lifestyle factors affecting their T2D status.
Additionally, they investigated the biological mechanisms related to heme iron’s link to T2D by examining a smaller group of participants. They assessed plasma metabolic markers from 37,544 individuals, focusing on insulin levels, blood sugar, blood fats, inflammation, and two iron metabolism markers. They also analyzed the metabolomic profiles of 9,024 participants, which included plasma levels of small-molecule metabolites resulting from bodily processes like digestion or chemical breakdown.
The results indicated a strong connection between higher heme iron intake and an increased risk of T2D. Individuals in the highest heme iron consumption group faced a 26% greater risk of developing T2D compared to those in the lowest consumption group. The researchers noted that heme iron contributed to over half of the T2D risk linked to unprocessed red meat and a notable share of the risk from certain dietary patterns related to T2D. Consistent with earlier studies, no significant relationship was observed between non-heme iron from food or supplements and T2D risk.
Furthermore, the study highlighted that greater heme iron consumption correlated with metabolic biomarkers associated with T2D. Higher heme iron intake was linked to increased levels of biomarkers like C-peptide, triglycerides, C-reactive protein, leptin, and markers of iron overload, while also correlating with reduced levels of beneficial biomarkers such as HDL cholesterol and adiponectin.
The researchers identified about a dozen blood metabolites—like L-valine, L-lysine, uric acid, and various lipid metabolites—that could be involved in the relationship between heme iron intake and T2D risk. These metabolites have been previously associated with higher T2D risk.
According to the researchers, the implications of these findings are significant for dietary recommendations and public health initiatives aimed at lowering diabetes rates. The research specifically raises questions about the use of heme iron in plant-based meat alternatives to improve their taste and appearance, which are becoming increasingly popular but require further health scrutiny.
“This research highlights the significance of making healthy dietary choices to prevent diabetes,” remarked Frank Hu, the corresponding author and Fredrick J. Stare Professor of Nutrition and Epidemiology. “Cutting down on heme iron intake, especially from red meat, and shifting towards a more plant-based diet can be effective strategies to reduce diabetes risk.”
The researchers acknowledged certain limitations in their study, such as the possibility of not fully accounting for confounding factors and errors in the epidemiological data. Moreover, since the study population was primarily white, the findings should be validated in other racial and ethnic groups.
Other contributors from Harvard Chan included Andrea Glenn, Anne-Julie Tessier, Danielle Haslam, Marta Guasch-Ferré, Deirdre Tobias, Heather Eliassen, JoAnn Manson, Kyu Ha Lee, Eric Rimm, Dong Wang, Qi Sun, Liming Liang, and Walter Willett.
