A randomised, double-blind, crossover study was performed to assess the impact of IMO as compared to SCF consumption on blood glucose, insulin and breath hydrogen responses in healthy young men and women. Subjects reported to the laboratory on five separate occasions (two familiarisations and three experimental days). On occasions one and two, subjects familiarised themselves with the breath hydrogen testing protocol. On occasions three to five, subjects were divided randomly into three conditions consisting of a non-calorie water-based placebo PLA, a bolus of IMO or SCF.

Ten men and women (aged 27.1 ± 2.7 years, body mass of 81.2 kg ± 4.4 kg, and an average height of 176.7 cm ± 2.8 cm) in the Tampa Bay, Florida, area were recruited for this study. No subject had any physical or medical health complications according to past health examinations, and all subjects were non-smokers for inclusion in this study. Participants were required to abstain from consuming any fibre supplements for one month prior to and during the washout period. The subjects completed a 12 h, overnight fast before the morning of the study and were instructed to avoid high-fibre items (> 5 g per serving) for 24 h before the experimental conditions. The IntegReview IRB (Austin, TX) #8100 approved all procedures for the study, which was carried out at the Applied Science and Performance Institute.

Randomly-assigned participants consumed a non-calorie water-based PLA, 25 g of IMO syrup (Tate & Lyle, PLC, United Kingdom) or 25 g of SCF syrup (Tate & Lyle, PLC, United Kingdom). Participants consumed both syrups as a liquid formulation by mixing 25 g of syrup with eight ounces of water and stirred until the solution was clear. A one-week washout period existed between experimental conditions. The identity of the conditions that were given to the participants remained unknown to both the participants and the primary researchers for the entire study. These solutions were labelled as A, B or C and given to the researchers working directly with the subjects to maintain a double-blinded method.

Subjects’ blood and breath hydrogen were taken at baseline and at 30, 60, 90, 120, 150 and 180 min following consumption of their respective solutions. Next, venous blood was collected from the antecubital vein using a 21-gauge needle into a 4 mL EDTA tube (BD Vacutainer^®, Becton, Dickinson and Company, Franklin Lakes, NJ) by a certified phlebotomist. Then, blood was prepped and assayed following the 180-min experiment for blood glucose and insulin. Finally, breath hydrogen was gathered in real time using a Gastro+ Gastrolyzer^® (coVita LLC, Santa Barbara, CA) according to the manufacturer’s instructions.

Before carrying out the parametric statistical analysis, dependent variables were examined for a normal distribution and outliers through investigation of boxplots and a normality test (e.g. Shapiro Wilk). No outliers were detected and data pasted normality testing (Table 1). Repeated measures analysis of variance (ANOVA) were used to scrutinise the effects of supplementation on dependent variables assuming group (SCF, IMO and PLA) and time (0, 30, 60, 90, 120, 150 and 180 min) as fixed factors (GraphPad Prism 7^®, La Jolla, CA). Whenever a significant F-value was obtained, a post-hoc test with a Tukey’s adjustment was performed for multiple comparison purposes. The significance level was previously set at p < 0.05. Results are expressed as mean ± standard error mean.

Regulation of blood glucose is highly sought after in our society. With the resurgence of low-carbohydrate, high-fat, ketogenic diets, it is essential to identify ingredients that do not significantly impact blood glucose or insulin. Our results demonstrated that IMO consumption led to a rise of nearly 50 mg/dL in blood glucose, with a concomitant five-fold rise in insulin at 30 min. However, no change was seen in SCF in either variable. Consequently, these results agreed with that of Kohmoto et al.⁴, who found that IMO were nearly 85% digested. Moreover, Cervantes-Pahm et al.⁸ and Kendall et al.⁹ found virtually no digestion in SCF, both in vivo and in vitro.

This study operationalised fermentation through the breath hydrogen technique. Resting levels of breath hydrogen are typically below 10 ppm; however, resting values in our study were approximately 4 ppm in all conditions. Our results demonstrated no change in the IMO condition relative to the PLA. Nevertheless, SCF increased to nearly four-fold to 120 min, and remained as such throughout the experiment. These results agreed with previous research, which demonstrated no change in breath hydrogen over 180 min following IMO consumption.¹⁰ It is important to note that two subjects showed no breath hydrogen response, which had previously been demonstrated to occur in over 15% of the population.^11,12 Also, prebiotic activity is indicative of digestibility. Using inulin as a standard, Oku et al.¹⁰ found very little prebiotic activity with IMO. More specifically, IMOs were 14 times less effective than inulin. In contrast, SCF was found to be equal to inulin in prebiotic activity and three to four times more tolerable.⁷