Higher consumption of heme iron, found in red meat and other animal products, is linked to a 26% increased risk of developing type 2 diabetes, underscoring the importance of opting for diets richer in vegetables and legumes.
A recent study led by researchers at the Harvard T.H. Chan School of Public Health found that higher consumption of heme iron, the type found in red meat and other animal products—as opposed to nonheme iron, which is found primarily in plant-based foods—is associated with an increased risk of developing type 2 diabetes. Although the link between heme iron and the disease has been noted in previous studies, the new findings further establish and explain this connection.
“Compared with previous studies that relied solely on epidemiological data, we integrated multiple layers of information, including epidemiological data, conventional metabolic biomarkers, and advanced metabolomics techniques,” said Fenglei Wang, senior author of the study and a research associate in the Department of Nutrition. “This allowed us to gain a more comprehensive understanding of the association between iron intake and type 2 diabetes risk, as well as the potential metabolic mechanisms underlying this relationship.” The study was published in Nature Metabolism.
To assess the relationship between iron and type 2 diabetes, researchers analyzed 36 years of dietary reports from 206,615 adults who participated in the Nurses’ Health Studies I and II and the Health Professionals Follow-up Study. They examined intake of various forms of iron—total, heme, nonheme, dietary (from food), and supplemental—and their relationship to type 2 diabetes status, controlling for other health and lifestyle factors.
In addition, the researchers analyzed the biological mechanisms underlying the relationship between heme iron and type 2 diabetes in smaller subsets of the participants. They studied plasma metabolic biomarkers from 37,544 participants, including those related to insulin levels, blood sugar, blood lipids, inflammation, and two biomarkers of iron metabolism. They also examined the metabolomic profiles of 9,024 participants, analyzing plasma levels of metabolites, which are substances derived from bodily processes such as the breakdown of food or chemicals.
A plant-based diet may reduce the risk of diabetes
The study revealed a significant association between higher heme iron intake and the risk of type 2 diabetes. Participants in the highest intake group had a 26% higher risk of developing type 2 diabetes compared with those in the lowest intake group. In addition, the researchers found that heme iron accounted for more than half of the risk of type 2 diabetes associated with consumption of unprocessed red meat and a moderate proportion of the risk associated with several dietary patterns related to this disease. In line with previous studies, no significant associations were found between non-heme iron intake, either through diet or supplements, and the risk of type 2 diabetes.
The study also identified that higher heme iron intake was linked to blood metabolic biomarkers associated with type 2 diabetes. Higher heme iron intake was associated with higher levels of biomarkers such as C-peptide, triglycerides, C-reactive protein, leptin, and iron overload markers, as well as lower levels of beneficial biomarkers such as HDL cholesterol and adiponectin.
The researchers also identified a dozen metabolites in the blood, including L-valine, L-lysine, uric acid and several lipid metabolites, that could play a role in the relationship between heme iron intake and the risk of type 2 diabetes. These metabolites have previously been associated with the risk of developing this endocrine disease.
“Reducing heme iron intake, especially from red meat, and adopting a more plant-based diet may be effective strategies to reduce diabetes risk.”
At a population level, the study’s findings have important implications for dietary guidelines and public health strategies to reduce diabetes rates, according to the researchers. In particular, the results raise concerns about the addition of heme iron to plant-based meat substitutes to improve their taste and appearance. These products are gaining in popularity, but their health effects require further research.
“This study underscores the importance of making healthy dietary choices to prevent diabetes,” said Frank Hu, senior author of the study and professor of Nutrition and Epidemiology. “Reducing heme iron intake, especially from red meat, and adopting a more plant-based diet may be effective strategies to reduce diabetes risk.”
The researchers noted that the study has some limitations, including possible underestimation of confounding factors and measurement errors in the epidemiological data. In addition, the findings—based on a predominantly white population—need to be replicated in other racial and ethnic groups.
