Dietary iron intake and Type 2 diabetes incidence in postmenopausal women: the Iowa Women's Health Study.
OBJECTIVE
Recently, a clear biological link between iron metabolism and diabetes has emerged from epidemiological and experimental studies. We carried out a prospective study of dietary iron intake and incidence of Type 2 diabetes.


METHODS
35,698 postmenopausal women initially aged 55 to 69 years were followed for 11 years. Diet was assessed with a food frequency questionnaire at baseline.


RESULTS
Intake of heme iron showed a positive association with incident Type 2 diabetes; the relative risks were 1.0, 1.07, 1.12, 1.14, and 1.28 across quintiles of heme iron (p trend =0.02) after adjustment for non-dietary and dietary risk factors. Heme iron showed a weak positive association among non-drinkers, but the association appeared to be stronger among subjects who consumed more alcohol. For example, in a model restricted to those who drank alcohol at least 15 g/day, adjusted relative risks across quintiles of heme iron were 1.0, 2.26, 3.22, 1.92, and 4.42 (p trend =0.05); and consumers of 30 g/day of more of supplemental iron had an adjusted relative risk equal to 3.03 (95% CI, 1.29-7.12)], compared to those who took no iron supplement. Non-heme iron was inversely associated with incidence of Type 2 diabetes. Amongst non-drinkers adjusted relative risks were 1.0, 0.83, 0.87, 0.72, and 0.67 across quintiles (p trend <0.01). This inverse association was lost among drinkers, in whom there was no association of diabetes incidence with non-heme iron.


CONCLUSIONS
Greater dietary heme-iron intake and/or supplemental iron were associated with an increased risk of Type 2 diabetes, especially amongst those who drink alcohol.
Lee
D-H
DH
Division of Epidemiology, School of Public Health, University of Minnesota, Minneapolis 55454, USA.
Folsom
A R
AR
Jacobs
D R
DR
D000368:Aged; D000428:Alcohol Drinking / Q000009:adverse effects; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology; D019587:Dietary Supplements / Q000009:adverse effects / Q000032:analysis; D004435:Eating; D002149:Energy Intake; D005260:Female; D006418:Heme / Q000032:analysis; D006801:Humans; D007484:Iowa / Q000453:epidemiology; D019266:Iron, Dietary / Q000009:adverse effects* / Q000032:analysis; D008460:Meat / Q000009:adverse effects / Q000032:analysis; D008875:Middle Aged; D015999:Multivariate Analysis; D018579:Patient Selection; D017698:Postmenopause; D011446:Prospective Studies; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects; D011795:Surveys and Questionnaires
D019266:Iron, Dietary; D006418:Heme