【Introduction】
Ingestion of oat β-glucan suppresses the postprandial blood glucose response by increasing the viscosity of the contents of the digestive tract and slowing down digestion and absorption, but the addition of oat β-glucan to food may change the taste and texture of the food, reducing its palatability.
In a previous study, the authors confirmed that oatmeal containing 0.9g, 2.3g, and 5.3g of oat β-glucan suppressed the postprandial glycemic response in a dose-dependent manner when taken a few minutes before eating white bread *1. However, it is not clear whether this effect is due to the amount of oat β-glucan or its viscosity.
The authors hypothesized that the viscosity of oat β-glucan would affect the glycemic response. The viscosity of a solution containing a fixed amount of oat β-glucan can be adjusted by changing the molecular weight of the oat β-glucan. In this study, we investigated the effect of different molecular weights, i.e., different viscosity, of 4 g of oat β-glucan on the postprandial glycemic response.
【Materials and Methods】
The subjects were 16 healthy men and women (41 ± 11 years, BMI 25.6 ± 2.7). After an overnight fast, six samples containing 4 g of oat beta-glucan were consumed with 200 ml of water (preloaded), and white bread containing 51.5 g of available carbohydrates was consumed with a drink (1 cup of coffee, tea, or water, either with 30 ml of milk or artificial sweetener, but the same drink each time) within 12 minutes. They were consumed within 12 minutes. As a control, two trials with only 200 ml of water as a preload were also conducted, for a total of eight trials in random order. The trials were conducted at least one day apart, up to a maximum of three times per week.
After consumption of the test meal, preference was evaluated using a visual analog scale (VAS) consisting of a 100 mm line with the leftmost line being "very unpalatable" and the rightmost line being "very palatable."
Blood glucose levels were measured before preloading, before the meal's start, and 15, 30, 45, 60, 90, and 120 minutes after the meal.
【Results】
All six samples were rated as significantly inferior in mouthfeel compared to the control. Palatability was not related to the molecular weight or viscosity of the samples.
The peak blood glucose levels and the incremental glucose area-under-the-curves (iAUCs) from 0 to 120 min were not significantly different among the oat β-glucans.
The increase in blood glucose levels of MW3 (153 kDa), MW4 (393 kDa), OP1 (1980 kDa), and OP2 (841 kDa) was smaller than that of the control at 15 and 30 minutes after the meal, and that of MW2 (76 kDa) was smaller at 90 minutes after the meal.
iAUCs of MW3, MW4, OP1, and OP2 from 0 to 45 min were lower than the control. MW4 and OP1 had a longer time to reach the peak blood glucose level than the control.
The analysis showed that the iAUCs from 0 to 45 minutes were 17%, 16%, and 20% lower with a 10-fold (1-log unit) increase in molecular weight, initial viscosity, and post-digestion viscosity, respectively. The peak blood glucose levels were 12, 14, and 15 minutes slower with a 10-fold increase in molecular weight, initial viscosity, and post-digestion viscosity, respectively.
【Discussion and Conclusion】
In this study, the peak blood glucose levels and the iAUCs from 0 to 120 minutes were not significantly different in each oat β-glucan. Moreover, the hypothesis that the higher the viscosity of oat β-glucan used for preloading, the less the postprandial blood glucose increase was not supported, but the iAUC from 0 to 45 minutes and the length of time it took for the blood glucose level to reach its peak related to viscosity.
In a previous study in which the authors used oatmeal with 0.9 g, 2.3 g, and 5.3 g of oat β-glucan added as a preload, only the 5.3 g sample had a lower iAUC from 0 to 120 min than the control, and the time, until peak blood glucose was reached, was longer [1]. The 4.0 g of oat β-glucan used in this study may not have been a sufficient dose.
Since OP1 used the same oatmeal as in the previous study, the results of OP1 were overlaying on the plots of iAUC from 0 to 45 min, iAUC from 0 to 120 min, peak blood glucose level, and time to peak blood glucose level in the previous study, and the results were consistent with a dose-dependent suppression of the postprandial blood glucose response. For high molecular weight oat β-glucans, the glycemic response was suggested to be dose-dependent.
【Research institution】
INQUIS Clinical Research, Ltd,
VTT Technical Research Centre of Finland Ltd,
School of Nutrition Sciences, University of Ottawa,
DSM Nutritional Products Ltd,
Department of Surgery, Division of Visceral and Transplantation Surgery, University Hospital Zürich
*1 Nutrients 8, 9, 524, 2016
Effect of Varying Molecular Weight of Oat β-Glucan Taken just before Eating on Postprandial Glycemic Response in Healthy Humans
Nutrients 12, 8, E2275, 2020
