A recent study by Harvard T.H. Chan School of Public Health researchers has further substantiated the connection between higher consumption of heme iron—found predominantly in red meat and other animal products—and an increased risk of developing type 2 diabetes (T2D). Unlike non-heme iron, primarily sourced from plant-based foods, this iron has been scrutinised in light of its health implications. The research findings reaffirm earlier reports linking heme iron to T2D and enhance our comprehension by incorporating a multifaceted approach to data analysis.
Lead author Fenglei Wang, a research associate in the Department of Nutrition, emphasised the novelty of their methodology. “Compared to prior studies that relied solely on epidemiological data, we integrated multiple layers of information, including epidemiological data, conventional metabolic biomarkers, and cutting-edge metabolomics,” Wang explained. This comprehensive approach allowed the team to delve deeper into the metabolic pathways influencing the relationship between iron intake and the risk of T2D. The study leveraged an extensive dataset, analysing 36 years of dietary reports from over 206,000 adults participating in the Nurses’ Health Studies I and II and the Health Professionals Follow-up Study. The researchers assessed the intake of heme and non-heme iron—both from dietary sources and supplements. They meticulously controlled various health and lifestyle factors to isolate the impact of iron on T2D status.
The research delved into biological mechanisms in addition to epidemiological data. For a subset of participants, plasma metabolic biomarkers were analysed—these included markers related to insulin levels, blood sugar, blood lipids, inflammation, and iron metabolism. Furthermore, metabolomic profiles were examined for another group of participants, which tracked plasma levels of small-molecule metabolites resulting from bodily processes such as food digestion or chemical breakdown.
The outcomes were telling. Participants with the highest heme iron intake had a 26% greater risk of developing T2D compared to those with the lowest intake. The study also illuminated that heme iron contributes significantly to the T2D risk associated with unprocessed red meat consumption and plays a moderate role in various dietary patterns linked to the disease. Unlike heme iron, intakes of non-heme iron from diet or supplements showed no significant associations with T2D risk.
Moreover, the study revealed that higher heme iron intake correlates with specific metabolic biomarkers associated with T2D. These include elevated levels of C-peptide, triglycerides, C-reactive protein, leptin, and markers of iron overload, alongside lower levels of protective biomarkers like HDL cholesterol and adiponectin. A dozen blood metabolites were identified as potentially significant in the relationship between heme iron intake and T2D risk, with previous studies linking them to increased diabetes risk.
The findings hold significant implications for public health, particularly concerning dietary guidelines to reduce diabetes rates. The increasing popularity of plant-based meat alternatives, often enhanced with heme to mimic the taste and appearance of meat, calls for a critical evaluation of their health impacts.
Corresponding author Frank Hu, the Fredrick J. Stare Professor of Nutrition and Epidemiology, pointed out the study’s broader significance. “This study underscores the importance of healthy dietary choices in diabetes prevention,” Hu stated. He advocated for reducing heme iron intake, especially from red meat, and shifting towards a more plant-based diet as practical strategies to lower diabetes risk.
Despite its strengths, the study acknowledges several limitations, including potential biases due to incomplete accounting for confounders and measurement errors in the data collection process. Additionally, since the study population was predominantly white, these findings must be replicated across diverse racial and ethnic groups to ensure generalizability.
More information: Fenglei Wang et al, Integration of epidemiological and blood biomarker analysis links haem iron intake to increased type 2 diabetes risk, Nature Metabolism. DOI: 10.1038/s42255-024-01109-5
Journal information: Nature Metabolism Provided by Harvard T.H. Chan School of Public Health
