Glycemic and Insulinemic Response to Ingestion of a Novel Food Bar Containing Whey Protein and Isomalto- Oligosaccharides

Special Article – Food Safety

Austin J Nutri Food Sci. 2018; 6(1): 1099.

Glycemic and Insulinemic Response to Ingestion of a Novel Food Bar Containing Whey Protein and Isomalto- Oligosaccharides

Grubic TJ¹, Sowinski R1,2, Dalton R¹, Collins PB¹, Reyes AG1,2, Favot CJ¹, Rasmussen C¹, Greenwood M1,2, Murano PS2, Earnest CP1,3 and Kreider RB1,2*

¹Department of Health & Kinesiology, Texas A&M University, USA

²Department of Nutrition and Food Sciences, Texas A&M University, USA

³Nutrabolt, 3891 S. Traditions Drive, USA

*Corresponding author: Kreider RB, Exercise and Sport Nutrition Lab, 118 Human Clinical Research Facility, Texas A&M University, College Station, Texas, 7743-4253 USA

Received: December 20, 2017; Accepted: February 22, 2018; Published: March 01, 2018

Abstract

This study examined the glucose and insulin response of ingesting a novel protein bar using a plant fiber (isomalto-oligosaccharides, IMO) as the carbohydrate source. In a randomized and crossover manner, 20 healthy men and women (Study 1) donated fasting blood samples prior to ingesting a Food Bar (FB) containing 20 g of a whey protein blend, 25 g of carbohydrate (13 g IMO, 4 g sugar, 8 g fiber), and 7 g of fat (1.5g saturated) or 25 g of dextrose (PLA). The experiment was repeated 7 to 10 days later while ingesting the alternative treatment. In study 2, 10 fasted individuals participated in the same experiment while ingesting 2 FB’s or 50 g of dextrose. Blood samples were taken at 10, 20, 30, 60, 90, and 120min post-ingestion while subjective ratings related to appetite and hypoglycemia were obtained at 0, 60 and 120 min. Data were analyzed by general linear model statistics and are presented as mean [95% CI] changes from baseline. Results revealed that the glycemic response to ingestion of the FB was significantly lower during the first 60 min following ingestion in comparison to the dextrose PLA. The glucose integrated AUC (iAUC) change from baseline was significantly lower with FB ingestion (Study 1 FB 60 [CI 48, 71], PLA 160 [134, 186], p<0.001; Study 2 FB 65 [49, 82], PLA 209 [170, 244] mmol-h/L, p<0.001) while no differences were observed between treatments in insulin iAUC responses. In comparison to the dextrose standard, the FB had an iAUC derived glycemic index (GI) of 34 [CI 23, 46] and a Glycemic Load (GL) of 8.5 [CI 5.6, 11.6]. Participants also reported significantly less subjective ratings of appetite and hunger and greater satisfaction from food and feeling of fullness in both studies. No significant differences over time or between treatments were observed in ratings of symptoms of hypoglycemia. Results indicate that ingestion of a whey protein bar using IMO as the source of carbohydrate elicited a low glycemic response in comparison to a reference carbohydrate in healthy individuals. Thus, this FB may serve as a low glycemic food option for individuals on a low glycemic diet and/or athletes interested in optimizing nutrient availability around exercise.

Keywords: Energy bars; Glycemic index; Glycemic load; Glycemic response to food

Introduction

Consumers often ingest carbohydrate and protein energy bars in between meals as snacks or prior to exercise in order to increase amino acid availability and/or maintain blood glucose during exercise [1-4]. However, many energy bars or drinks have a relatively high Glycemic Index (GI) and therefore may not be not suitable for individuals who are glucose intolerant and/or diabetic [3,5]. Additionally, while it is recommended that athletes ingest carbohydrate and protein prior to exercise [1,4], ingesting foods, gels, and/or beverages that have high GI’s may promote hypoglycemia during exercise and thereby hasten fatigue [1,3,4,6,7]. For example, we previously reported that ingestion of moderate to low GI carbohydrate gel during prolonged cycling maintained blood glucose and insulin levels to a greater degree than a higher GI gel [7]. Additionally, that adding different types of carbohydrate with low to high GI’s to whey protein had differential effects on glucose and insulin responses following intense resistanceexercise [6].

Isomalto-oligosaccharides (IMO) are a prebiotic high fiber, low calorie source of carbohydrate that has been used as a functional food and sweetener in Asia for over 3 decades [8-12]. Basic animal studies indicate that IMO’s serve as a soluble dietary fiber and can stimulate activity of the probiotic gut flora, improve gut function, and help manage cholesterol in animals fed on a high fat diet [8,11,13-15]. Given the interest in developing food and energy bars that provide quality protein with a low to moderate glycemic profile, we sought to determine the glycemic and insulinemic responses of ingesting a whey protein food bar with IMO as the source of carbohydrate. Our primary outcome was assessment of the glycemic insulinemic responses to ingesting this Food Bar (FB). The secondary outcome was assessment of how ingestion of this FB affected appetite related variables and subjective ratings of hypoglycemic symptoms. We hypothesized that ingestion of a mixed ingredient food bar containing IMO would promote a low to moderate glycemic response and positively affect perceptions about appetite with no evidence of hypoglycemia.

Methods

Experimental design

This study was conducted with approval by an Institutional Review Board (IRB2016-0830D) and was registered with clinicatrials. gov (#NCT03166514). This study was conducted in two parts at a university-based research setting in randomized, counter-balanced, and crossover manner. In both studies, the independent variable was nutrient intake and dependent variables included blood glucose, insulin, and subjective ratings related to appetite and hypoglycemic side effects.

Participants

Apparently healthy men and women between the ages 18–35 years with a Body Mass Index (BMI) less than 25 kg/m2 were recruited to participate in this study. Individuals who expressed interest in participating were screened by phone or email to determine if they met initial eligibility to participate in this study. Qualified individuals were invited to attend a familiarization session in which participants received a written and verbal explanation of the study design, testing procedures, and read and signed informed consent statements. Those giving consent completed personal and medical histories and had height, weight, blood pressure, and heart rate determined. There search coordinator reviewed medical history forms, physical examination measurements, and determined eligibility to participate. Participants were excluded from the study if they reported: 1.) any uncontrolled metabolic disorders or cardiovascular disorder, including heart disease, a history of hypertension, diabetes, thyroid disease, hypogonadism; 2.) hepatorenal, musculoskeletal, autoimmune, or neurological disease; 3.) they were currently taking prescribed medication or dietary supplements for thyroid, hyperlipidemia, hypoglycemia, anti-hypertensive, anti-inflammatory, or weight loss (e.g. thermogenic compounds) within three months before the start of this study; or, 4.) Had any known allergies to some of the nutrients contained in the food bar (i.e., almonds, milk, soy, peanuts, tree nuts, egg, and wheat).

Nutritional intervention

In a placebo controlled, counterbalanced, and crossover manner, participants ingested a carbohydrate and protein food bar (FB, FitJoy™, Nutrabolt, Bryan TX) containing 20 g of a whey protein blend, 25 g of carbohydrate (13 g fiber and 4 g of sugar) as IMO plant fiber (VitaFiber™, BioNutra North America, Inc. Edmonton, Alberta, Canada), and 7g of fat (1.5g saturated) or 25 goof dextrose (PLA, Valeant Pharmaceuticals North America LLC, Bridgewater, NJ, USA). After a 7 to 10-day washout period, participants repeated the experiment while ingesting the remaining nutrient. In Study 1, participants ingested one Food Bar (FB) containing 220 calories and one 25 g serving of the PLA providing 100 calories (i.e., typical serving size) while in Study 2 participants ingested two FB’s and two 25 g servings of the dextrose PLA in order to assess the glycemic responses to ingesting a standard oral glucose tolerance test dose (i.e., 50 g). Participants were given as much time as needed to ingest the nutrients but this typically was less than 3-5 minutes.

Testing sequence

Figure 1 presents the general experimental design employed in both studies. For each experiment, participants were instructed to refrain from exercise for 24 h and fast for 10 h prior to reporting to the lab for testing. Once arriving at the lab, body weight was determined, participants completed appetite and hypoglycemia symptom related questionnaires, and they donated a fasting blood sample. Participants then ingested their assigned nutrient and a timer was started. Blood samples were obtained at 10, 20, 30, 60, 90 and 120 min post-ingestion while responses to questionnaires were obtained 60 and 120 minutes after ingestion of the assigned nutrient. Participants observed a 7 to 10-day washout period and then repeated the experiment in a crossover manner while ingesting the remaining nutrient.