All prebiotics that nourish microorganisms of bowel flora are fibers that humans are unable to digest: you ingest them, they pass through the stomach, upper small intestine, then reach the farthest portions of the small intestine and colon, and are then consumed by various microbial species. Bacteria, in turn, metabolize fibers to fatty acids, such as butyrate, that nourish and heal the delicate intestinal lining and exert spectacular health effects, such as reduced insulin (which thereby contributes to loss of visceral fat and weight loss), reduced blood sugar, reduced blood pressure, reduced triglycerides, and rise in HDL. There is a growing appreciation for the brain and emotional effects of healthy bowel flora, also, with improved mood, reduced depression, reduced anxiety, deeper sleep with more vivid dreams. The bowels themselves also benefit with improved bowel regularity, reduced intestinal inflammation, and reduced potential for diverticular disease and colon cancer. Healthy intake of prebiotic fibers is life- and health-transforming.
Prebiotic fibers differ based on what sugars (all fibers are made of sugars) make up the chain. Cellulose from plants and wood, for instance, largely indigestible by humans (and the fiber of bran cereals that bulk up stool), is made of chains of glucose sugar molecules, while fructo-oligosaccharides, or FOS, and inulin are made up of fructose sugars. (FOS contains 10 or less fructose molecules, while inulin contains greater numbers.)
Galacto-oligosaccharides, or GOS, are a collection of prebiotic fibers made up a chain of galactose sugars of variable length. It is one of the prebiotic fibers found naturally in human milk, suggesting a potentially beneficial role in breastfeeding infants and onwards. GOS has been shown to exert some of the most potent and beneficial effects among prebiotic fibers. Among the recent findings in studies with GOS supplementation:
- GOS added to infant formula (4 grams/liter) given to formula-fed infants was associated with changes in bowel flora that approximated the bowel flora composition of breast fed infants: increased Bifidobacteria and Lactobacillus, decreased Clostridia: Giovannini et al 2014. Incidentally, colic was reduced in the group receiving the prebiotic. (A higher concentration of galacto-oligosaccharides of 8 grams/liter were not as well tolerated with more watery stools and spitting up: Williams 2014.)
- GOS combined with FOS and omega-3 fatty acids decreased the number of respiratory infections in children: Chatchatee 2014.
- GOS 5.5 grams per day reduced several markers of inflammation, such as tumor necrosis factor and c-reactive protein: Vulevic 2008 (In this study, a somewhat different form of GOS, a trans form, was used.)
- GOS, 4 grams twice per day (total 8 grams per day), given to adults over 50 substantially increased the numbers of Bifidobacteria: Walton 2012.
- GOS, 2.5 grams three times per day (total 7.5 grams per day) partially mitigated the adverse effects of the antibiotic, amoxicillin, on Bifidobacteria populations: Ladirat 2014.
- GOS 5 to 10 grams per day, but not 2.5 grams per day, increased Bifidobacteria populations: Davis 2014.
- In an experimental mouse model of colitis, GOS dramatically reduced colon inflammation and increased Bifidobacteria populations: Gopalakrishnan 2012.
- GOS given to children, 2 grams per day, doubled the population of Bifidobacteria over 3 weeks: Pirainen 2008.
- GOS, 5.5 grams per day given to people over 64 years old, increased Bifidobacteria and was associated with significant improvements in several aspects of the immune response: Vulevic 2008.
- GOS can reverse lactose intolerance in many individuals, likely due to increase in lactose-fermenting Bifidobacterium, Faecalibacterium, and Lactobacillus: Azcarate-Peril 2017
- More than inulin, GOS may exert greater nutritive effects on some beneficial bacterial species: Watson 2013, Rycroft 2001.
In the Wheat Belly Blog post, Cultivate the garden called “bowel flora,” I discussed some of the ways we can nourish and cultivate bowel flora using prebiotic fibers. However, there may be additional benefit in specifically increasing intake of the GOS form of prebiotic to the 5 grams per day or so range that will compound the benefits of, say, using inulin, FOS, or raw potatoes. We also, you will recall, aim to achieve species diversity: blocking the proliferation of undesirable species while cultivating a large array of healthy species, much as primitive humans unexposed to modern life display.