Fasting serum hippuric acid is elevated after bilberry (Vaccinium myrtillus) consumption and associates with improvement of fasting glucose levels and insulin secretion in persons at high risk of developing type 2 diabetes

Scope: Urinary hippuric acid has been proposed as a biomarker for fruit, vegetable, and polyphenol consumption. We assessed how serum hippuric acid changes after a bilberry-enriched diet (BB; high anthocyanin intake) and another berry diet including strawberries, raspberries, and cloudberries (SRC; lower anthocyanin intake) and how these changes associate with insulin and glucose metabolism. Methods and results: Hippuric acid was measured with LC-QTOF-MS metabolite profiling analysis from fasting serum samples at baseline and after an 8-week intervention in 47 individuals with features of the metabolic syndrome who were randomized to either a BB diet (n = 15), an SRC diet (n = 20) or a control diet (n = 12). Fasting serum hippuric acid increased significantly (3.5-fold, p = 0.001) only in the BB group and correlated with changes in fasting plasma glucose concentration (r = –0.54, p < 0.05) and insulin secretion (r = 0.59, p < 0.05). These associations were confirmed in the Finnish Diabetes Prevention Study (n = 198). Conclusion: Fasting serum hippuric acid is increased after consumption of anthocyanin-rich bilberries, and may contribute to the beneficial effect of bilberry consumption through its associations with better glycemic control and β-cell function.