Evidence check: HbA1c in the context of Darmgesundheit

HbA1c (glycated hemoglobin) is a well-established marker for average blood glucose control over the past 2–3 months, primarily used in diabetes diagnosis and monitoring. There is no direct, clinically validated link between HbA1c and gut health. However, basic research suggests that the gut microbiome can influence insulin sensitivity and glucose metabolism via short-chain fatty acids (e.g., butyrate). Some observational studies show that a high-fiber diet benefits both the gut microbiota and is associated with lower HbA1c levels. Nevertheless, the evidence for a causal pathway from gut health to HbA1c reduction remains weak and mostly mechanistic or observational. In clinical practice, HbA1c is not used as a marker for gut health. Direct-to-consumer tests that present HbA1c in a gut health context often overstate the scientific basis. A healthy, fiber-rich diet is beneficial for both domains, but an isolated HbA1c value without diabetes risk factors tells little about the state of the gut.