Purpose
Despite equivocal human study data, anthocyanin-rich blueberries are associated with
positive glycaemic effects which could benefit satiety and other cardiometabolic
outcomes. The objective of this study was to examine the dose-dependent effects of
freeze-dried wild blueberries on postprandial glucose response simultaneously with
changes in satiety, blood pressure and cognitive function.
Methods
Twenty-four healthy participants (F = 22), mean BMI 22.9 kg/m²
and mean age 28 years
were recruited to a randomized crossover study in which they received a carbohydrate rich breakfast with a wild blueberry or placebo-matched drink (250 mL) providing 0, 150,
300 or 450 mg anthocyanins. At baseline and at 30 min intervals during the 3-hour
postprandial phase, blood pressure, subjective appetite ratings and gastrointestinal satiety
hormones from a plasma sample (up to 150 min) were recorded. Blood glucose was
measured using continuous glucose monitoring. Cognitive performance was assessed at
baseline and 90 min post-meal consumption.
Results
Postprandial glucose and insulin levels declined in a dose-dependent manner. Medium
and high doses showed significantly lower glucose and insulin compared to control during
the first hour. Concurrently, satiety hormones GLP-1, PYY, and GIP demonstrated
significant increases, most pronounced at the highest dose (450 mg anthocyanins),
although subjective appetite was unaltered. Cognitive assessments using the Visual
Verbal Learning Test, Corsi test and Rapid Visual Information Processing test revealed
no significant intervention effects and blood pressure was unaffected.
Conclusion
Wild blueberry effects on postprandial glucose and appetite hormone responses were
evident at anthocyanin doses of 300 mg and above but did not impact other outcomes in
healthy adults. Further studies should include individuals with metabolic and/or cognitive vulnerability in longer term interventions to confirm benefits of wild blueberries.
Trial registration
ISRCTN11726069, 15/11/2024, retrospectively registered
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)