Blueberry anthocyanin supplementation shows favorable trends in glycemic control and alters the gut microbiota in type 2 diabetes patients: a pilot study

Abstract

Growing evidence supports the hypoglycemic potential of blueberry anthocyanins, though clinical data remain limited. This study aimed to evaluate the effects of blueberry anthocyanin extract (BAE) supplementation on glycemic control and gut microbiota composition in patients with type 2 diabetes mellitus (T2DM). This 6-month pilot study included 15 elderly T2DM patients, who received either 400 mg day⁻¹ BAE (n = 8) or no supplement (n = 7). Glycemic parameters, gut microbiota (analyzed via 16S rRNA sequencing), and fecal short-chain fatty acids (SCFAs) were assessed at the baseline and after 1, 3, and 6 months. While statistically significant improvements in glycemic parameters were not achieved, favorable trends in fasting glucose and HbA1c were observed upon BAE intervention. Notably, BAE supplementation significantly altered gut microbiota composition by reducing the relative abundance of Firmicutes and increasing Bacteroidota (P < 0.05) and elevated SCFA levels, though the latter change was not statistically significant. Correlation analysis further revealed associations between specific bacterial genera, glucose metabolism indicators, and SCFAs. These findings suggest that BAE may modulate the gut microbiota and improve glucose metabolism in T2DM, supporting its potential as a dietary adjunct for glycemic management, although larger trials are needed for confirmation.