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High Heme-iron Intake May be Associated with Increased Risk for Type 2 Diabetes

Heme-iron intake from red meat may be associated with an elevated risk for type 2 diabetes, according to new research from the Harvard School of Public Health.

Type 2 diabetes often occurs in patients with haemochromatosis, a disease of massive iron overload, and this observation has led to the suggestion that high iron stores may increase the risk for diabetes. However, previous studies investigating the association between iron stores and diabetes risk have been inconclusive.

Investigators led by Rui Jiang, of Boston, Massachusetts, Unites States, performed a prospective study to examine the relationship between dietary iron intake and history of blood donations with the incidence of type 2 diabetes in a large cohort of men. These factors were chosen for the study because dietary iron is the predominant source of body iron stores, whereas blood donation is known to effectively reduce iron stores.

Data for the analysis was obtained from the Health Professional's Follow-up Study (HPFS), a 12-year prospective investigation examining the aetiologies of major diseases in 51,529 male health professionals aged 40 to 75 years. Dietary information was assessed for the participants every 4 years using a semiquantitative food-frequency questionnaire, and additional questionnaires were used biennially to obtain information on disease status and health behaviours.

For the present analysis, investigators asked the participants during the sixth year of the HPFS to report their total number of blood donations in the previous 30 years. A supplementary questionnaire was also used to confirm reports of diabetes from the biennial health status report, and 1168 incident cases of type 2 diabetes were identified during the 12-year follow-up.

Heme iron intake was found to be significantly associated with an increased risk for type 2 diabetes. The risk for men in the highest quintile of heme iron relative to those in the lowest quintile was 1.28 (95% CI: 1.02, 1.61; P = .045 for trend) in multivariate analysis, which adjusted for multiple confounding factors including age, BMI, and family history of diabetes. A similar association with diabetes was found for heme-iron intake from red meat (RR: 1.63; 95% CI: 1.26, 2.10; P < .001), but not for heme-iron intake from alternative sources.

In contrast, neither total iron intake nor non-heme iron was significantly associated with diabetes in multivariate analysis. Furthermore, no association was identified between blood donation and diabetes risk.

"Heme-iron intake from red meat appears to be associated with an increased risk of type 2 diabetes, but our study was unable to determine whether the association was due to heme iron per se or to other components of red meat," the researchers conclude. They recommend further studies to examine direct measures of body iron stores in relation to diabetes risk.

Am J Clin Nutr 2004 Jan;79:1:70-5. "Dietary iron intake and blood donations in relation to risk of type 2 diabetes in men: a prospective cohort study"

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