What are PRObiotics and PREbiotics?
Probiotics are living bacteria cells that are cultured in the lab under specific conditions(Usually Billions of colony-forming) and encapsulated. The World Health Organization(WHO) defines probiotics as live bacteria that, when administered in adequate amounts, confer a health benefit on the host”(Han et al., 2021). So we expect probiotics to arrive at the small and/or large intestine to interact with existing gut bacterial flora and exert positive health effects on our bodies.
Prebiotics, on the other hand, are non-digestible food ingredients that help the beneficial bacteria that are already inhabiting our intestines to grow. Prebiotics can also be prepared in a particular manner in the lab and put in the capsule for further ingestion. Usually, It’s a good idea to combine prebiotics and probiotics to increase the chance of those bacteria taking a residence in our guts, though there is very limited knowledge about how to do this successfully. This remains an active area of research. Additionally, how much probiotics per day should be taken remains a major question. The common knowledge seems to be that the probiotic culture must be ingested continually, to obtain a continuous positive effect on the gut microflora. (Bezkorovainy, 2001; Judkins et al., 2020)
Probiotics, their effect on the body and on bloating, specifically.
The two major probiotic strains that are dominant on the market nowadays are Bifidobacteria and Lactobacillus. Both of these microbes are lactic acid fermentation bacteria, meaning that they “eat” specific sugar(mostly lactose in milk) to produce lactic acid, hence the sour taste of their cultures. But besides producing lactic acid in the gut, various Bifidobacterium species can ferment non-digestible foods(fiber) such as salep(or starch in general) to produce Short Chain Fatty Acids(SCFAs)(Usta-Gorgun, B et al.,2020). SCFAs are very important to human health according to a very extensive body of research. For example, SCFAs are shown to have anti-inflammatory, antitumorigenic, and antimicrobial effects; and increase gut barrier integrity.(Tan et al., 2014; Visekruna and Luu, 2021). While having such an amazing variety of health effects, those molecules are essentially volatile gasses and when in excess may be the cause for the gut expansion effect – bloating.
Let’s evaluate the extent of bloating that can be potentially caused by SCFAs’ overproduction. This effect was studied by in-vitro(outside of human cultures and in the lab) fermentation of intestinal bacteria of different starchy foods(Kaur et al., 2011). Taking the data from the article we can calculate the approximate amount of gas that can be produced in the first 4 hours of fermentation. For example, for 100g of non-digested starches, 2 to 20 liters of gas is produced. Just to get a visual comparison 20 liters of gas is enough to fill 1.5 average balloons. The majority of produced SCFAs will be absorbed in the gut fairly quickly.
Note that not too many diets will allow for more than 100g of fiber per meal, (e.g. legumes-heavy plant-based vegan diet). In fact, the standard American diet(SAD) will only supply 16g of fiber per day on average. Therefore somebody following the SAD diet and taking SCFA fermentation probiotics continuously should not expect too much bloating based on those alone. On the other hand, one should consider the beneficial effects that SCFAs will have on his/her health. Moreover, SCFAs produced by probiotics are not the only potential source of bloating. There are other well-known sources of gases that can contribute to bloating – methane or hydrogen sulfide gas, for example. This latter, which is the primary cause of foul flatulence smell, can be produced by sulfate-reducing bacteria in the human gut. Additionally, even the swallowed air during the food ingestion can contribute to the amount of gas in the colon. However, it is not usually attributed to the cause of bloating.
It is fair to say that excessive gas or bloating can be caused by major probiotic strains when combined with fiber-rich diets, but the effects of those beneficial gases cannot be overlooked. Moreover, not all probiotics produce SCFAs, and there is emerging evidence that some probiotic strains will actually reduce the amount of gas produced in the gut. Therefore I recommend that one should perform some research into the probiotic strains they are targeting for consumption.
Han, S., Lu, Y., Xie, J., Fei, Y., Zheng, G., Wang, Z., Liu, J., Lv, L., Ling, Z., Berglund, B., et al. (2021). Probiotic Gastrointestinal Transit and Colonization After Oral Administration: A Long Journey. Front. Cell. Infect. Microbiol. 0.
Kaur, A., Rose, D.J., Rumpagaporn, P., Patterson, J.A., and Hamaker, B.R. (2011). In vitro batch fecal fermentation comparison of gas and short-chain fatty acid production using “slowly fermentable” dietary fibers. J. Food Sci. 76, H137–H142.