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Xylooligosaccharides: The Low-dose Prebiotic

By Prof. Gene Bruno, MS, MHS, RH(AHG)

Huntington University of Health Sciences

Dietary prebiotics are typically non-digestible fiber compounds that pass undigested through the upper part of the gastrointestinal (GI) tract and stimulate the growth or activity of friendly, probiotic bacteria that colonize the large bowel by acting as substrate for them.1 In the world of dietary supplements, there are several prebiotics from which to choose—perhaps the best known of which is fructooligosaccharides. Whatever the type, one feature which they all have in common is that several grams are typically required in order to provide clinical benefit. There is, however, one exception to this: xylooligosaccharides (XOS), which have been shown to provide prebiotic benefits with just a 1.032 to 1.4 g dose.

What is XOS?
XOS are mainly composed of two or three xylose units with beta-1,4 linkages. They are obtained by hemicellulose hydrolysis, which is relatively abundant in the cell walls of grains. XOS increases the number of intestinal Bifidobacterium in humans and maintains the fecal water content within the normal range.2

What is the Evidence?
In a double-blind, randomized, placebo-controlled study,3 healthy adult subjects (n = 32) received 1.4 g XOS, 2.8 g XOS or placebo in daily doses. The study consisted of a two-week run-in, an eight-week intervention, and a two-week washout phase. Stool samples were collected at baseline, after four and eight weeks of intervention and two weeks after cessation of intervention. Samples were subjected to culture, pyrosequencing of community DNA, pH and SCFA analyses. Tolerance was evaluated by daily symptom charts. The results were that XOS was tolerated without significant gastrointestinal side effects, and Bifidobacterium counts increased in both XOS groups compared to the placebo subjects. The 1.4 g per day group had significantly higher Bifdobacterium counts compared to the placebo group subjects at eight and 10 weeks. The researchers concluded that XOS supplementation “may be beneficial to gastrointestinal microbiota” and “The low dose required, and lack of GI side effects makes the use of XOS as a food supplement feasible.”

It should be noted that in the aforementioned XOS study, the minimum effective dose of 1.4 g was based upon a 70 percent XOS material. Therefore, 0.98 g XOS was the yield (i.e. 1.4 X 70 percent = 0.98). However, a 95 percent XOS material is also available, so only 1.032 g would be necessary to yield the same 0.98 g.  Either way, it appears that XOS offers the lowest effective dose of any prebiotic currently in use.


  1. Hutkins RW, Krumbeck JA, Bindels LB, Cani PD, Fahey G Jr, Goh YJ, Hamaker B7, Martens EC, Mills DA, Rastal RA, Vaughan E, Sanders ME. Prebiotics: why definitions matter. Curr Opin Biotechnol. 2016 Feb;37:1-7.
  2. Tateyama I, Hashii K, Johno I, Iino T, Hirai K, Suwa Y, Kiso Y. Effect of xylooligosaccharide intake on severe constipation in pregnant women. J Nutr Sci Vitaminol (Tokyo). 2005 Dec;51(6):445-8.
  3. Finegold SM, Li Z, Summanen PH, Downes J, Thames G, Corbett K, Dowd S, Krak M, Heber D. Xylooligosaccharide increases bifidobacteria but not lactobacilli in human gut microbiota. Food Funct. 2014 Mar;5(3):436-45.

Professor Gene Bruno, MS, MHS, the Provost for Huntington College of Health Sciences, is a nutritionist, herbalist, writer and educator. For more than 37 years he has educated and trained natural product retailers and health care professionals, has researched and formulated natural products for dozens of dietary supplement companies, and has written articles on nutrition, herbal medicine, nutraceuticals and integrative health issues for trade, consumer magazines and peer-reviewed publications. He can be reached at gbruno@hchs.edu.