Dietary fibre refers to nutrients in the diet that gastrointestinal enzymes do not digest. If properly labelled, dietary fibres should not significantly elevate blood glucose or insulin and should ferment in the large intestine. Because of the recent rise in low-carbohydrate products on the market, consumers use these various fibres without adequate knowledge concerning whether or not these ingredients affect any blood parameters and constitute a dietary fibre. The aim of this study was to examine the impact of isomaltooligosaccharides (IMO) as compared to soluble corn fibre (SCF) consumption on blood glucose, insulin and breath hydrogen responses in healthy young men and women. After an overnight fast, nine individuals consumed 25 g of either placebo (PLA), IMO or SCF. Breath hydrogen was significantly higher in the SCF condition than in the IMO and PLA at 90, 120, 150 and 180 min (
Dietary fibres are non-digestible carbohydrates in the diet that, when consumed, pass through the small intestine into the large intestine where colonic microflora may partially or wholly ferment them.
Isomaltooligosaccharides primarily derive from exposure of the maltose-rich syrup to the transglucosidase enzyme
Numerous companies and nutrition products include and list both IMO and SCF as fibre sources. However, to date, research has not examined the comparison of these two carbohydrates
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 (
Baseline values of dependent variables.
Variable | SCF | IMO | PLA | |
---|---|---|---|---|
4 ± 3 | 4 ± 3 | 3 ± 3 | 0.699 | |
82 ± 8 | 83 ± 9 | 86 ± 9 | 0.635 | |
3.8 ± 2.3 | 4.1 ± 2.4 | 4.0 ± 2.8 | 0.908 |
IMO, isomaltooligosaccharides; PLA, placebo; SCF, soluble corn fibre.
Of the 10 subjects, nine completed the trial, while one withdrew from the study because of nausea associated with measures taken during baseline testing. Thus, all data are reported based on the final subject pool. A group by time interaction was demonstrated for breath hydrogen response (
(a) Group hydrogen responses, (b) glucose group responses (c) insulin group responses.
Individual breath hydrogen responses to (a) soluble corn fibre, (b) isomaltooligosaccharides and (c) placebo.
Individual blood glucose responses to (a) soluble corn fibre, (b) isomaltooligosaccharides and (c) placebo.
Individual insulin responses to (a) soluble corn fibre, (b) isomaltooligosaccharides and (c) placebo.
Group breath hydrogen response in parts per million (ppm).
Condition | 0 min | 30 min | 60 min | 90 min | 120 min | 150 min | 180 min |
---|---|---|---|---|---|---|---|
4 ± 1 | 5 ± 1 | 7 ± 2 | 9 ± 3 |
16 ± 4 |
17 ± 4 |
16 ± 4 |
|
4 ± 1 | 4 ± 1 | 2 ± 1 | 2 ± 1 | 1 ± 1 | 2 ± 1 | 1 ± 0 | |
3 ± 1 | 4 ± 1 | 3 ± 1 | 3 ± 1 | 2 ± 1 | 1 ± 1 | 0 ± 0 |
IMO, isomaltooligosaccharides; PLA, placebo; SCF, soluble corn fibre.
SCF significantly higher than PLA (
SCF significantly higher than IMO (
SCF significantly higher than IMO and PLA (
Group blood glucose response in mg/dL.
Condition | 0 min | 30 min | 60 min | 90 min | 120 min | 150 min | 180 min |
---|---|---|---|---|---|---|---|
82 ± 3 | 89 ± 4 | 83 ± 4 | 84 ± 5 | 81 ± 4 | 82 ± 4 | 82 ± 3 | |
83 ± 3 | 132 ± 6 |
91 ± 6 | 84 ± 4 | 85 ± 4 | 85 ± 4 | 86 ± 3 | |
86 ± 3 | 88 ± 4 | 86 ± 3 | 87 ± 4 | 87 ± 4 | 85 ± 4 | 85 ± 3 |
IMO, isomaltooligosaccharides; PLA, placebo; SCF, soluble corn fibre.
IMO significantly higher than SCF and PLA (
Group insulin response in μIU/mL.
Condition | 0 min | 30 min | 60 min | 90 min | 120 min | 150 min | 180 min |
---|---|---|---|---|---|---|---|
3.8 ± 0.8 | 5.4 ± 1.2 | 4.5 ± 0.9 | 4.5 ± 0.9 | 3.5 ± 0.9 | 3.8 ± 0.8 | 3.3 ± 0.8 | |
4.1 ± 0.8 | 22.0 ± 3.7 |
9.4 ± 1.1 |
6.0 ± 0.9 | 4.3 ± 0.8 | 3.9 ± 0.5 | 3.9 ± 0.5 | |
4.0 ± 0.9 | 4.2 ± 1.0 | 4.2 ± 1.0 | 3.7 ± 0.6 | 3.4 ± 0.7 | 3.7 ± 0.7 | 3.0 ± 0.5 |
IMO, isomaltooligosaccharides; PLA, placebo; SCF, soluble corn fibre.
IMO significantly higher than SCF and PLA (
IMO significantly higher than PLA (
IMO significantly higher than SCF (
The purpose of this study was to investigate the impact of IMO as compared to SCF consumption relative to the PLA on blood glucose, insulin and breath hydrogen responses in healthy men and women. The primary findings of this study were that SCF did not raise either blood glucose or insulin as compared to PLA. However, SCF produced a significant rise in breath hydrogen, indicating that it arrived in the large intestine intact and was fermented by bacteria. In contrast, IMO produced a robust rise in blood glucose and insulin 30 min after meal consumption and did not increase breath hydrogen. Following is a discussion of each of these variables.
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.
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.
Previous research combined with this study’s results collectively indicate that of the two carbohydrate sources examined, SCF – but not IMO – can be listed on food labels as a dietary fibre source. Given its versatility in food preparation, SCF appears to be a viable option for manufacturers to produce high-fibre, palatable food-based products that would support a low-carbohydrate, ketogenic diet.
The authors would like to thank Daniel Orrego and Ron Penna for their thoughtful insights into this study design.
Leftover funds from a project supported by Quest Nutrition were used to pay for the blood analysis for this study. Quest Nutrition sells nutritional products that use soluble corn fibre.
The authors declare that they have no financial or personal relationships which may have inappropriately influenced them in writing this article.
R.P.L. was the project leader. J.M.W assisted with experimental and project design. A.B., M.H.S., C.I., W.A.L., and M.S assisted with experimental and project design and helped with data collection. G.J.W, M.D.R. and R.W. helped oversee the draft and final version of the manuscript.