Myths vs facts: Cortisol and blood sugar

Cortisol, the primary stress hormone, raises blood sugar by stimulating gluconeogenesis in the liver and reducing insulin sensitivity. This is a normal, short-term response to provide energy during stress. A common myth is that cortisol is always harmful or that a DNA test can tell you if you are 'cortisol-resistant'. In reality, the link between chronic cortisol elevation and sustained high blood sugar is well-established: it can lead to insulin resistance, prediabetes, and type 2 diabetes. However, direct-to-consumer (DTC) genetic tests claiming to personalize diet based on cortisol-related genes lack scientific support. Most associated SNPs have tiny effect sizes and are overshadowed by lifestyle factors like sleep, exercise, and stress management. The fact is: a balanced diet, regular physical activity, and stress reduction are the most effective ways to keep both cortisol and blood sugar in check—regardless of genetics. The evidence for the cortisol–blood sugar relationship is strong (human-strong), but applying it to nutrigenetic testing remains speculative.