SLC30A8 and type 2 diabetes mellitus: As supplemental zinc is more bioavailable than zinc from food sources [16], and as iron has been shown to inhibit the absorption of zinc [17, 18], we set out to examine zinc intake from both food sources and supplements, the zinc to iron ratio in relation to T2D, and particularly, potential effect modification by the SLC30A8 rs13266634 genotype.