Isomalto-Oligosaccharides: A Complete Guide to This Protein Bar Ingredient
Manufacturers create isomalto-oligosaccharides using enzyme-catalyzed hydrolysis on starch derived from cereal crops (e.g. wheat, barley, and corn), pulses (e.g. lentils and peas), rice, tapioca (cassava), potatoes.  IMOs are typically 91% oligosaccharides, 2% glucose, and 7% various high molecular weight molecules (n>=11). 
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IMOs are 60 to 70% as sweet as sucrose (sugar), less viscous than maltose, and are partially digestible, containing about 2.0-2.4 calories per gram.  This article will discuss the benefits, downsides, food sources, and supplement sources of isomalto-oligosaccharides.
Combat Crunch bars contain 210 calories, 7g fat, and 20g protein. IMOs are the second ingredient on the label behind the proprietary protein blend. Order now.
Benefits of Isomalto-OligosaccharidesIsomalto-oligosaccharides are prebiotics, which mean they pass through the small intestine relatively undigested and then arrive in the colon to be fermented by your body's gut bacteria.  In comparison probiotics are the beneficial bacteria found in your digestive tract that combat harmful bacteria and ensure you absorb the nutrients from the food you eat.
Prebiotics are food for probiotics so they cause positive changes in "both the composition and/or activity in the gastrointestinal microflora."  Compared to The number of human and animal studies supporting the healthful effects of isomalto-oligosaccharides are rapidly growing.
A small study on healthy adult men and senile people found isomalto-oligosaccharides positively benefit gut bacteria. Six adult men (26-48 years old) and eighteen senile people (males and females 50+ years old) consumed 13.5 grams of IMOs daily for 10 and 14 days, respectively. At the end of the study researchers found that the average number of beneficial bifidobacteria significantly increased from 109.4 to 1010 in healthy males and 108.3 to 109.4 in senile people.
IMOs also killed off harmful enterobacteria, which includes bacteria like salmonella, Escherichia coli, and shigella. Unsurprisingly those with the lowest initial amount of bifidobacteria saw the most substantial increases - up to 100 times more after the trial period.  These increases in health-promoting probiotics can help with nutrient absorption and immune system function.
Seven older males consumed a low fiber diet for 30 days and then added 10 grams of isomalto-oligosaccharides for 30 days without changing their nutrient intake. Although body measurements did not change significantly defection frequency increased by 200%, wet stool weight increased by 70%, dry stool weight increased by 55%, and microbial fermentation increased by almost 250% without adverse side effects. 
Thirteen constipated elderly males and females consumed a four-week placebo diet followed by an eight-week period of ingesting 10 grams of isomalto-oligosaccharides daily. IMO supplementation not only increased healthy gut organisms (bifidobacteria, lactobacilli, and bacteroides), defection frequency, and fecal mass but it also decreased harmful clostridia bacteria and low-density lipoprotein cholesterol (LDL-C) levels. 
IMOs were also found to produce the least amount of gas compared to other prebiotics like fructo-oligosaccharides and xylo-oligosaccharides.  Moderate quantities of IMOs have profound effects on gastrointestinal motility and gut health for constipated individuals and those eating a low fiber diet.
In the rat animal model isomalto-oligosaccharides significantly increased the number of lactobacilli and bifidobacteria diversity without adverse side effects compared to rats consuming control and inulin diets.  A second study confirmed these findings as well as found that IMOs significantly increased immune-boosting Immunoglobulin A (IgA) in the feces, Interferon-? (IFN-?) production in the intestines, as well as natural killer (NK) T cells in the liver and spleen. 
The benefits of IMOs appear to go beyond the gastrointestinal tract. These findings are promising for both maintaining good health and recovering from illness.
Downsides of Isomalto-Oligosaccharides
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Isomalto-oligosaccharides are touted as a low-glycemic sweetener safe for diabetics but some studies found less than favorable results for its impact on blood sugar. When six fasted human subjects consumed 25 grams of IMO syrup under resting conditions their average blood glucose levels increased from 109mg/L to 136mg/dL and insulin levels increased from 4.8 ?U/mL to 32 ?U/mL 30 minutes post-ingestion. 
A 24.8% increase in blood glucose and 566.7% increase in blood insulin levels suggest that IMOs are far from low-glycemic. This was a very small study and we should not be surprised to find that nearly one ounce of a sweet carbohydrate on an empty stomach impacts blood sugar and insulin levels. In contrast a study on young healthy adults found that daily a IMO consumption of 15 grams did not negative impact lipid concentration and glucose absorption. 
Regardless, these findings reaffirm that IMOs should be used in moderation, are not a free-pass to binge on carbohydrates, and do physiologically impact the body despite being classified as fiber according United State Department of Agriculture (USDA). Consuming more than 30 grams of isomalto-oligosaccharides per day may cause undesirable minor gastrointestinal issues like gas, bloating, and soft stool.  Those consuming more than two protein bars with IMOs as the primary carbohydrate source are likely ingesting more than 30 grams.
One study found a daily consumption of 1.5 grams per kilogram of bodyweight to be the threshold of inducing diarrhea due to IMO overconsumption. This translates to 120 grams for an 80kg/176lb individual, or six to seven protein bars using large quantities of IMOs. Two studies found bifidobacteria decreased almost back to baseline 14 to 28 days after IMO supplementation ceased.  If consumed intermittently rather than chronically then isomalto-oligosaccharides may not be a permanent fix for increasing probiotic content in the gut.
What Foods and Supplements Contain Isomalto-Oligosaccharides?Isomalto-oligosaccharides are found in select foods and are increasing in popularity as a sweetener in protein bars. Small amounts of isomalto-oligosaccharides are naturally present in fermented foods like miso, soy sauce, and sake.6 Of the free sugars in these foods only about 5 or 10% are isomaltose.  The sugar isomaltose is also found in honey, a natural sweetener packed with phytonutrients. 
In the past few years the supplement industry dramatically increased its use of isomalto-oligosaccharides in protein bars. This plant-based lower calorie sweetener is high in prebiotic fiber and low on the glycemic index. When used in protein bars IMO syrup can decrease the carbohydrate and calorie content, increase the dietary fiber content, and preserve the protein bar's flavor and texture.
The list below discussed six popular protein bars that use isomalto-oligosaccharides:
Controlled Labs Venture Bar - One 69g bar has 220 calories, 9g fat, 30g carbohydrates, 20g fiber, 5g sugar alcohols, and 20g protein. IMOs are the first ingredient listed on the label; before whey protein isolate.
Oh Yeah! Victory Bar - One 65g bar has 200 calories, 6g fat, 28g carbohydrates, 20g fiber, and 21g protein. IMOs are the second ingredient listed on the label behind the proprietary protein blend.
Muscle Pharm Combat Crunch - One 63g bar has 210 calories, 7g fat, 28g carbohydrates, 12g fiber, 1g sugar alcohols, and 20g protein. IMOs are the second ingredient on the label behind the proprietary protein blend.
Oh Yeah! ONE Bar - One 60g bar has 210 calories, 7g fat, 24g carbohydrates, 10g fiber, 11g sugar alcohols, and 21g protein. Isomalto-oligosaccharides are the second ingredient on the label behind the proprietary protein blend.
Julian Bakery Paleo Protein Bar - One 60g bar has 170 calories, 5g fat, 28g carbohydrates, 22g fiber, and 20g protein. IMOs are the second ingredient listed on the label behind egg whites.
Isomalto-oligosaccharides are plant-based prebiotic carbohydrates that positively impact digestion, bowel movement quality and frequency, as well as beneficial bacteria in the gut. Although not calorie-free, IMOs contain fewer calories and more fiber than traditional sweeteners like table sugar. When consumed in moderation as a part of a high-protein diet IMOs may assist in nutrient absorption and fat loss.
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2) Rycroft, C.E. , Jones, M.R. , Gibson, G.R. and Rastall, R.A. (2001), A comparative in vitro evaluation of the fermentation properties of prebiotic oligosaccharides. Journal of Applied Microbiology, 91: 878-887. doi:10.1046/j.1365-2672.2001.01446.x
3) Lee, Hyeon Cheol et al. "Isomaltose Production by Modification of the Fructose-Binding Site on the Basis of the Predicted Structure of Sucrose Isomerase from "Protaminobacter Rubrum." Applied and Environmental Microbiology 74.16 (2008): 5183?5194. PMC. Web.
4) Zhu, Jianhua. "GRAS exemption claim for Isomalto-oligosaccharide or IMO." United States Food and Drug Administration. BioNeutra Inc., 6 June 2005. Web.
5) Slavin, Joanne. "Fiber and Prebiotics: Mechanisms and Health Benefits." Nutrients 5.4 (2013): 1417-1435. PMC. Web.
6) Kohmoto, Takanobu, et al. "Effect of Isomalto-oligosaccharides on Human Fecal Flora." Bifidobacteria Microflora 7.2 (1988): 61-69. Web.
7) Chen, H. L., et al. "Effects of isomalto-oligosaccharides on bowel functions and indicators of nutritional status in constipated elderly men." The Journal of the American College of Nutrition (2001): 44-49. Web.
8) Yen, C. H., et al. "Long-term supplementation of isomalto-oligosaccharides improved colonic microflora profile, bowel function, and blood cholesterol levels in constipated elderly people--a placebo-controlled, diet-controlled trial." Nutrition (2011): 445-450. Web.
9) Ketabi, A., L. A. Dieleman, and M. G. Gänzle. "Influence of isomalto-oligosaccharides on intestinal microbiota in rats." Journal of Applied Microbiology 110.5 (2011): 1297-1306. Wiley Online Library. Web.
10) Mizubuchi, Hiroyuki, et al. "Isomalto-Oligosaccharides Polarize Th1-Like Responses in Intestinal and Systemic Immunity in Mice." The Journal of Nutrition 135.12 (2005): 2857-2861. Web.
11) Hertzler, Steve. "IMO Syrup in Nutrition Bars: Not As Guilt-free As We Think." EAS Academy. Abbott Nutrition, 2012. Web.
12) Hondo, Satoshi, and Tsutomu Mochizuki. "Free Sugars in Miso." Nippon Shokuhin Kogyo Gakkaishi 26.11 (1979): n. pag. Web.