Association between iron intake with diet and diabetes and impaired fasting glucose among PURE Poland study participants

Abstract Introduction Different studies results show that higher iron intake and increased iron stores in the body are significantly associated with a higher risk of diabetes mellitus (DM), a risk factor for cardiovascular diseases. Iron metabolism in the body is associated with the production of free oxygen radicals, which, combined with the stressful effect of glycation end products in pre-diabetes, increases the risk of diabetes and cardiovascular events. The purpose of the study was to assess the relationship between iron intake with diet and diabetes and impaired fasting glucose among PURE Poland study participants. Methods Study group consisted of 1889 individuals (1185 women and 704 men, aged 35-70 years, from urban and rural area), who were participants of the Polish arm of the Prospective Urban Rural Epidemiology (PURE) study. The study was approved by the Ethics Committee. The data were collected between 2007-2009, in the first stage of the PURE Poland study. Diabetes was diagnosed when fasting glucose level was ≥ 126 mg/dl or there was a declaration about DM occurrence in the medical interview. Diagnosis of impaired fasting glucose (IFG) was made when fasting glucose level was between 100-125 mg/dl with no statement about DM in the interview. Analysis were conducted for DM+IFG in three models: 1. crude data, 2. adjusted for energy intake, 3. adjusted for energy intake, age, body mass index and smoking. Food Frequency Questionnaire (FFQ) was used to assess food intake. FFQ was developed and validated for this population within the PURE study. Iron intake with diet was calculated based on the data from FFQ. For further analysis the study group was divided into tertiles based on the daily iron intake with diet, separately for men and women. Results The prevalence of DM+IFG in each tertile (T) of iron intake with diet was: 27.6% (T1), 37.0% (T2) and 38.7% (T3) among women, and 30.3% (T1), 40.9% (T2) and 37.9% (T3) among men. Taking into account crude data the OR (95% CI) for DM+IFG among women was 1.54 (1.14-2.08) in T2 and 1.66 (1.23-2.24) in T3 when comparing with T1. In model 2 the OR (95% CI) for DM+IFG among women was 1.63 (1.16-2.28) in T2 and 1.88 (1.21-2.94) in T3 when comparing with T1. In model 3 in the group of women the OR (95% CI) for DM+IFG was 1.52 (1.07-2.16) and 1.62 (1.02-2.56) when comparing T2 vs T1 and T3 vs T1, respectively. In the group of men in model 1 the OR (95% CI) for DM+IFG prevalence was 1.59 (1.08-2.32) in T2 vs T1 and 1.40 (0.95-2.05, p>0.05) in T3 vs T1. In the group of men in model 2 and 3 the results were not statistically significant, both in T2 vs T1 and T3 vs T1. Taking into account the whole study group the risk of DM+IFG was significantly higher in T2 vs T1 (model 1, 2 and 3) and in T3 vs T1 (model 1 and 2). Conclusions Higher iron intake with diet was associated with a higher risk of diabetes and impaired fasting glucose in the study group, especially among women.