Key Findings:
North Americans, on average, only consume about ½ of the recommended levels of fiber per day. Of interest from the physiological standpoint are soluble fibers which modulate postprandial metabolism due to their viscosity. In this study, two sets of dairy products (thickened beverages and gelled puddings) were developed to investigate potential differences between fluids versus gelled food matrix in terms of postprandial response. Soy-soluble polysaccharide addition to a 50 glucose solution did not modulate postprandial glucose or insulin nor did viscosity-matched samples containing flaxseed gum (0.7%) or guar gum (0.23%). Sample viscosity may have been too low to exert an effect. The measured viscosity of samples prior to gastrointestinal exposure may not be reflective or predictive of physiological effects. Reductions in glucose AUC and GI following consumption of dairy beverages with 1% fiber (soy-soluble polysaccharide or flaxseed gum), were noted even when differences in product viscosity were present. Glucose AUC and GI decline with increasing viscosity for the fiber-fortified dairy study treatments and significantly lower peak glucose concentrations were observed relative to the reference.
ABSTRACT:
Objective: Soy-soluble polysaccharides and flaxseed gum are underutilized dietary fibers of interest to the food industry. However, because the ability of soluble fibers to modulate postprandial glucose and insulin metabolism has been related to their viscous effects, the utility of these and other low-viscosity soluble fibers remains unproven. The objective of this study was to examine the associations between soy-soluble polysaccharides and flaxseed gum concentration, product viscosity, and the postprandial glycemic and insulinemic responses in the context of glucose solutions as well as fluid and gelled dairy products. Methods: Twelve healthy males participated in a randomized crossover postprandial study in which they visited the laboratory following overnight fasts on 11 occasions to consume one of 11 study treatments, each consisting of 50 g available carbohydrates. The study treatments included a glucose reference (in duplicate), glucose solutions containing soy-soluble polysaccharides (6%), flaxseed gum (0.7%), or guar gum (0.23%), all matched for an apparent viscosity of 61 mPa·s at 50 s−1, as well as dairy-based beverages and puddings with 0% or 1% soluble fiber added. Blood samples were collected at fasting and up to 2 hours postprandially for determination of glucose and insulin concentrations. Area under the curve (AUC), peak concentration, and time-to-peak values as well as glycemic index (GI) and insulinemic index (II) were calculated.
Results: Fiber fortification of a 50 g glucose solution had no effect on postprandial blood glucose or insulin levels, even at a high concentration (i.e., 6% soy-soluble polysaccharides). Glucose AUC and GI values for the dairy-based beverage (p < 0.05) and pudding (p < 0.01) controls were significantly lower than the glucose reference. Glucose AUC and GI values for the soy-soluble polysaccharide-fortified dairy products (p < 0.01) and flaxseed gum–fortified dairy products (p < 0.001) were significantly lower than the glucose reference. No significant differences were observed between the fiber-fortified fluid and gelled dairy-based study treatments and no significant differences were observed in terms of the insulin AUC, II, and peak insulin concentration between any of the dairy products. Conclusions: All dairy products had lower glycemic responses relative to the reference, with no effect of beverage versus pudding matrix observed and minimal impact of 1% flaxseed gum or soy-soluble polysaccharides. Product apparent viscosity, but not fiber concentration, was significantly and inversely correlated with glucose AUC and GI. (Authors abstract)
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