New research shows there is no sufficient evidence to prove an interaction between dietary and genetic variables influencing iron status and the risk for incident type 2 diabetes, according a study published in Diabetes Care.
In this case-cohort study, investigators evaluated the association between the interactions of dietary and genetic variables influencing iron status and incident type 2 diabetes in 9347 and 12,301 case and subcohort participants, respectively. The case group was composed of individuals with a verified incident type 2 diabetes diagnosis, whereas the subgroup acted as a control.
Among the participants consuming meat or other iron-containing foods, there was a direct association between the meat or iron item and ferritin concentrations. Specifically, a higher heme iron intake per 1 standard deviation correlated with greater ferritin levels (β = 0.113; 95% CI, 0.082-0.144). There was no association, however, between higher heme intake and transferrin (β = −0.019; 95% CI, −0.043 to 0.006) or transferrin saturation (β = 0.016; 95% CI, −0.006 to 0.037).
Single nucleotide polymorphisms, particularly rs1799945 (located in the HFE H63D gene) and rs855791 (located in the TMPRSS6 gene), were associated with ferritin and significantly differed between sexes (Psex_diff <.05). In addition, rs1800562 (HFE C282Y), rs236918 (PCK7), and rs744653 (SLC40A1) single nucleotide polymorphisms correlated with ferritin. Researchers found no interaction of heme iron and the ferritin-related gene score in regard to diabetes risk (Padd =.16; Pmult =.21) overall; however, there was a trend toward a negative interaction among male participants (Padd =.04; Pmult =.03).
Self-reported dietary questionnaires used in this study could have resulted in errors related to the dietary intake values of iron-containing foods. Although the sex-specific effects could have related to the different iron requirements among men and women, they may also be related to residual confounding among the women.
Although the findings demonstrate that the risk for type 2 diabetes is higher among individuals genetically predisposed to higher ferritin who also have high intake of heme iron, the investigators suggest “the risk may be lower than expected from the sum or product of the two individual exposures.”
Meidtner K, Podmore C, Kröger J, et al. Interaction of dietary and genetic factors influencing body iron status and risk of type 2 diabetes within the EPIC-InterAct study [published online November 22, 2017]. Diabetes Care. doi:10.2337/dc17-1080