Acute Consumption of Blueberries and Short-Term Blueberry Supplementation Improve Glucose Management and Insulin Levels in Sedentary Subjects

Abstract

Background: Blueberries are polyphenol-rich fruits with antioxidant and anti-inflammatory properties. Polyphenols from berries act by blocking digestive enzymes, reshaping gastrointestinal microbiota, and affecting the release of gastrointestinal hormones to regulate insulin dynamics and glucose management. However, most studies use fruit extracts instead of fresh fruit. We aimed to evaluate postprandial glucose management and antioxidant capacity of fresh blueberries consumed acutely or as a six-day supplementation in 10 sedentary subjects.

Methods: To evaluate the effect of acute blueberry intake, 150 g of blueberries were consumed together with 150 g of white bread by the subject and blood samples were collected at 0, 30, 60, 90 and 120 min to measure glucose, insulin, and plasma antioxidant capacity. To evaluate supplementation, 150 g of blueberries were provided daily for six days and sample collection was performed at day 7.

Results: Acute consumption of blueberries decreased postprandial glucose area under the curve (AUC) and increased insulin levels at 15 min timepoint. Supplementation did not affect glucose levels but decreased insulin levels at 120 min. No changes in antioxidant capacity were observed.

Conclusions: Consumption of fresh blueberries improves postprandial glucose management presumably due to actions on the gastrointestinal tract, while supplementation improves insulin sensitivity, probably due antioxidant and anti-inflammatory effects.

Keywords: antioxidant; blueberries; glucose management; insulin; polyphenols; sedentary subjects.

Figure 1

Design of the acute intervention and short-term supplementation. Acute intervention and short-term supplementation were separated by 2 weeks (WK).

Figure 2

Glucose and insulin results after acute fresh blueberry consumption (Ac). (A) Basal fasting glucose levels. (B) Basal fasting insulin levels. (C) Glucose curve after 150 g of white bread consumption. (D) Insulin curve after 150 g white bread consumption. (E) Area under the curve (AUC) of plasma glucose after 150 g of white bread consumption. (F) Area under the curve (AUC) of plasma insulin after 150 g of white bread consumption. * p < 0.05 vs control or t = 0, ** p < 0.01 vs control or t = 0.

Figure 3

Glucose and insulin results after short-term fresh blueberry supplementation (Suppl). (A) Basal fasting glucose levels. (B) Basal fasting insulin levels. (C) Glucose curve after 150 g of white bread consumption. (D) Insulin curve after 150 g white bread consumption. (E) Area under the curve (AUC) of plasma glucose after 150 g of white bread consumption. (F) Area under the curve (AUC) of plasma insulin after 150 g of white bread consumption. * p < 0.05 vs. control.

Figure 4

Plasma glutathione levels and antioxidant capacity measured by FRAP assay after acute consumption (Ac) and short-term blueberry supplementation (Suppl) compared to baseline levels (control). (A) GSH in acute consumption. (B) GSH in short-term supplementation. (C) GSH/GSSG in acute consumption. (D) GSH/GSSG in short-term supplementation. (E) FRAP in acute consumption. (F) FRAP in short-term supplementation. Baseline levels are shown by white bars while grey bars represent treatments. * p > 0.05 vs control, ** p < 0.01 vs control, *** p < 0.001 vs. control and **** p < 0.0001 vs. control. GSH: expressed as mM; GSSG: expressed as mM; FRAP: expressed as mg/dl.