In the first large study to assess iron stores and risk of type 2 diabetes in an apparently healthy population, researchers from the Harvard School of Public Health (HSPH) found that higher iron stores were associated with significantly elevated risk of type 2 diabetes, independent of other known diabetes risk factors. Higher iron stores were assessed by measuring blood concentrations of ferritin (a protein that stores iron in the body). The findings appear in the Feb. 11 issue of the Journal of the American Medical Association (JAMA).
More than 32,800 women participants were selected from the ongoing Brigham and Women’s Hospital-based Nurses Health Study. The participants had provided blood samples between 1989 and 1990 and were free of diabetes, cardiovascular disease, and cancer. Over a 10-year span of follow-up, participants provided information on diet and lifestyle via questionnaires. Some 698 women were diagnosed with type 2 diabetes during the course of the study, with a total of 716 healthy women selected as controls.
Compared with the healthy controls, women who developed type 2 diabetes during the course of the study had significantly elevated ferritin levels when blood samples were initially drawn. Compared with women with the lowest ferritin concentration, those with higher ferritin levels had a nearly three-fold increased risk of developing type 2 diabetes during the 10 years of follow-up. Adjusting for obesity and other diabetes risk factors, including family history of diabetes, physical activity, smoking status, alcohol consumption and diet did not change the results.
Adequate iron is important for health because it is essential for oxygen transport and cell functions. Excess levels of iron, however, can increase cellular oxidative stress and can damage tissues because iron is a potent pro-oxidant. This may lead to insulin resistance and abnormal glucose metabolism, elevating risk of type 2 diabetes.
“The results provide the strongest evidence to date that increased iron stores in the body are an independent risk factor for type 2 diabetes,” said Rui Jiang, lead author and a research fellow in the Department of Nutrition at HSPH.