We're gonna get super sciencey in here, I was on a research roll. If it goes over your head, don't worry, I wrote it for practitioners.
According to research from Liu, et al. (2017) Fructooligosaccharide (FOS) and Galactooligosaccharide (GOS) supplementation in healthy young individuals, was shown to increase relative abundance beneficial Bifidobacterium. Normally, this would seem positive, except for the consequence whereby butyrate-producing bacteria (i.e. Phascolarctobacterium and Ruminococcus) were reduced.
Butyrate is a short chain fatty acid synthesised by some microbes which works to transport fluid, dampen mucosal inflammation (inhibition of NF-kB) and oxidation, modulate visceral sensitivity (through ion absorption and GLP-1) and intestinal motility (Canai, et al. 2011). Whilst not the most significant of the short chain fatty acids (60% acetate, 25% propionate), butyrate has a key role in homeostatic chain reactions which impact health (Canai, et al. 2011).
FOS more significantly reduced butyrate-producing bacteria, when compared to GOS. However, in the Liu, et al. (2017) study, the source of the FOS was hydrolysed sucrose rather than extracted from foods or mixed with inulin (another prebiotic fibre). Perhaps the nature of the FOS and the dose (the maximum) produced a different effect that noted in other studies.
In a realistically healthy diet, volume of FOS (e.g. fruit and veg) and GOS (e.g. legumes) would be quite low compared to ingested volume of resistant starch (e.g. whole grains, legumes, & green bananas). Resistant starch is one of the prebiotic sources that encourage butyrate production, remembering that FOS and GOS tend to reduce the bacteria which produce this (Davani-Davari, et al. 2019). Other prebiotics include oligosaccharides such as pectin, and non-carbohydrate oligosaccharides, such as flavanols found in cocoa. Davani-Davari, et al. (2019) further mention that natural sources of GOS and FOS do not quantify a “prebiotic effect” and they must therefore be manufactured. Most of these prebiotics stimulate Bifidobacterium, a beneficial and naturally dominant family (Davani-Davari, et al. 2019; Liu, et al. 2017; Slavin, 2013). In most cases, whereby there isn’t a specific [strain of] pre/probiotic which improves symptomatology, a mixture of prebiotic sources should be included to support multiple families of beneficial microbes, and their respective diversity.
Canai, R., Costanzo, M., Leone, L., Pedata, M., Meli, R. & Calignano, A. (2011). Potential beneficial effects of butyrate in intestinal and extraintestinal diseases. World Journal of Gastroenterology, vol 17. Issue 12. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3070119/
Davani-Davari, D., Negahdaripour, M., Karimzadeh, I., Seifan, M., Mohkam, M., Masoumi, S., Berenjian, A. & Ghasemi, Y. (2019). Prebiotics: Definition, Types, Sources, Mechanisms, and Clinical Applications. Foods, vol 8. Issue 3. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6463098/
Liu, F., Li, P., Chen, M., Luo, Y., Prabhakar, M., Zheng, H., He, Y., Qi, Q., Long, H., Zhang, Y., Sheng, H. & Zhou, H. (2017). Fructooligosaccharide (FOS) and Galactooligosaccharide (GOS) Increase Bifidobacterium but Reduce Butyrate Producing Bacteria with Adverse Glycemic Metabolism in healthy young population. Scientific Reports, vol 7. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5603605/
Slavin, J. (2013). Fiber and Prebiotics: Mechanisms and Health Benefits. Nutrients, vol 5. Issue 4. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3705355/