Myths vs facts: Selen and Blutzucker

Selenium is an essential trace element that functions as a cofactor for selenoproteins such as glutathione peroxidases, which protect against oxidative stress and support thyroid metabolism. A common myth is that selenium supplementation lowers blood sugar or prevents diabetes. The evidence is mixed: some observational studies suggest an inverse association between selenium levels and diabetes risk, but randomized controlled trials (RCTs) indicate that supplementation above the recommended dietary allowance (55–70 µg/day) may actually increase diabetes risk, especially in well-nourished individuals. The tolerable upper intake level (UL) is 300–400 µg/day; exceeding it is linked to higher diabetes incidence. Another myth is that a genetic variant like GPX1 rs1050450 alone justifies supplementation. In reality, the effect of this SNP on selenium metabolism is small, and supplementation without a confirmed deficiency can be harmful. High selenium status has been associated with insulin resistance and type 2 diabetes in several RCTs. Therefore, selenium is not a blood-sugar-lowering agent. The evidence is mixed: mechanistic and observational data conflict with RCT outcomes. Practical advice: meet selenium needs through diet (Brazil nuts, fish, eggs) and only supplement after a blood test and medical consultation. Safety note: do not exceed the UL without professional guidance.