Randomized Controlled Crossover Dose-Response Trial Shows Low Dose (2 g) Barley β-Glucan Provided in Waffles Lowers Post-Prandial Glycaemic Response In Healthy Adults

Objectives
Barley β-glucan (BG) has reported post-prandial (PP) glycemic response lowering effects. The objective of this study was to ascertain the minimum and most effective dose of BG on PP glucose and insulin response using waffles as the test food.

Methods
Healthy adults (7 men/17 women) completed a randomized controlled crossover trial at the Asper Research Institute in Winnipeg, MB. Each participant attended five 2.5-hour study visits separated by 3–14 days (average = 7 days). At each visit participants ate waffles containing 30 g available carbohydrates (AC) with varied doses of BG (0, 2, 4, or 6 g). Wheat waffles with low fibre and protein (0g-1) and wheat waffles matched to BG waffles for insoluble dietary fibre and protein (0g-2) were used as controls. The order of treatments was random. Fasting, 15, 30, 45, 60, 90 and 120 minute PP capillary blood samples were collected for analysis of blood glucose and plasma insulin levels. Data were analyzed using analysis of covariance with treatment, participant, visit number and interaction between treatment and visit number included in the model. Differences (P ≤ 0.05) among treatments were determined using least square means adjusted using the Tukey option.

Results
There was a significant effect of treatment on both glucose and insulin iAUC (P < 0.0001). Glucose iAUC was 31–40% lower after eating 2, 4 and 6 g BG waffles compared to both 0 g waffles. Glucose iAUC was not significantly different between 0 g waffles or among BG waffles. Insulin iAUC was not significantly different between 0 g waffles. Insulin iAUC was 32% lower after eating 2 g BG compared to 0g-1, but not significantly different from 0g-2 waffles. Insulin iAUC was 36–58% lower after eating 4 and 6 g BG compared to both 0 g waffles, and 38% lower after eating 6 g BG compared to 2 g BG waffles.

Conclusions
The low dose (2 g BG per 30 g AC) provided a physiological benefit (reduction in PP glucose response >20%). Increasing dose to 4 or 6 g BG did not provide additional glucose lowering benefits, but insulin response decreased as BG dose increased. Lack of difference in glucose and insulin iAUC between the two 0 g control waffles (insoluble fibre 1 g vs 8 g; soluble fibre 0 g), but higher PP glycemic responses than BG waffles emphasizes that the type of fibre is key to PP glycemic responses.

Funding Sources
Agriculture and Agri-Food Canada.