How Probiotic, Prebiotics, and Synbiotics Influence the Gut Microbiome.
The human gut microbiome has received an incredible amount of attention in recent years. It has been determined that there are more bacterial cells in the gut microbiome than we have in the entire human body. In fact, the human gut microbiome has roughly 3.3 million unique genes, which his 150 times greater than our own human genome [9]. As a result, its influence on metabolism, the immune system, cognitive function, disease, and overall human health is significant.
Our gut microbiome is influenced the moment we are born into this world. Even the birthing process and location, natural birth vs. cesarean section, homebirth vs. hospital, can have a dramatic impact on the development of the microbiome, both in bacterial diversity and bacterial count [8]. As we age, our environment, illness, stress, diet, medication, and physical activity can all play a large role in determining the makeup of the gut microbiome.
As a result, the use of probiotic and prebiotic supplements are on the rise. But can these supplements have enough of an impact to create positive change?
Probiotics are considered live microorganisms, that when given to a host, may result in health benefits. The addition of live bacteria to the gut is believed to improve the composition and activity of the gut microbiome, and as a result, improve the health of the gastrointestinal system [1]. The use of fermented foods for health benefits, specifically dairy, can be dated back to 5000 B.C. Hippocrates, Galen, and Avicenna advocated using fermented milks for the treatment of gastrointestinal illnesses. The most common probiotic species are Lactobacillus, Bifidobacterium, and Saccharomyces boulardii. Commonly, they are used to treat conditions such as IBS, constipation, dysbiosis, intestinal permeability, or even post antibiotic consumption. However, their utilization can be seen in treatments of other conditions such as eczema, anxiety, depression, SIBO, allergies, and reoccurring infections. It is important to note that not all probiotic strains exist in the human gastrointestinal system, and any benefits experienced from a specific strain cannot be generalized to other strains [7]. This is important, as individual probiotic strains create specific responses in the body, and the treatment of such conditions should require individualized prescriptions, rather than generalized probiotic usage. It is becoming common practice to recommend or prescribe probiotics, without identifying the species and strain necessary to treat those conditions. In addition, some probiotics are only effective at certain dosages, rendering them ineffective if not consumed in proper amounts. Research proves that most strains are only effective when utilized at doses ≥ 1,000,000,000 (1 billion) colony forming units (CFU’s) [3]. If a formula contains multiple strains, each strain must contain 1 billion CFU’s, or it is highly likely that the supplement will be ineffective.
Prebiotics, on the other hand, are non-digestible food substances, that may positively benefit the host by promoting the growth or activity of the pre-existing bacteria in the colon. These substrates, mostly derived from carbohydrates and specifically oligosaccharides, ferment within the large intestine. Through the addition of prebiotics, there may be a shift in the microbiota of the host, resulting in health benefits. For food ingredients to be classified as prebiotics, they must bypass the stomach and small intestine without being hydrolyzed or absorbed, act as a selective substrate for commensal bacteria found in the large intestine, alter the microflora ecosystem towards a healthier composition, and induce a luminal or systemic change that improves the health of the host. These are commonly found in foods such as asparagus, chicory, onions, garlic, artichoke, and even breast milk [1]. The most common prebiotics are lactulose, galacto-oligosaccharides (GOS), and fructo-oligosaccharides (FOS). Lactulose is commonly used to treat dysbiosis, candidiasis, constipation, and endotoxemia. GOs is used for dysbiosis, GIT infections, IBS, and traveler’s diarrhea. And FOS is used in the treatment of dysbiosis, immune deficiencies, and damaged intestinal mucosa. Prebiotics differ from probiotics in terms of effective dosages. Because these food substances ferment in the large intestine, there is a greater risk of adverse side effects if the dose or frequency of consumption is too high. Therefore, it is best to start with small doses, and slowly build up tolerance.
When probiotics and prebiotics are combined, they are referred to as synbiotics. Due to the wide range of health benefits that probiotics and prebiotics offer, combined with our understanding of how gut health can influence the rest of the body, researchers are looking into how this combination can positively impact health [5]. Sadly, many of the probiotics and prebiotics are combined into supplements without considering specificity of strains, or proper dosages to infer a benefit to the host. A meta-analysis conducted by Marx et al., (2020) addressed the connection between probiotics and prebiotics, and their ability to improve cognitive function, memory, and executive function. However, results for their study did not support the use of prebiotics, probiotics, or fermented foods for cognitive function. This may be a result of improper species and strains used, limited dosage of probiotics, or due to the heterogeneity of the population studied. Until future studies take into account specificity of species and strain, it is highly unlikely that synbiotics will be able to treat a wide spectrum of diseases and disorders, as most do not contain strain specificity or the proper dosage to infer a benefit.
Likewise, the promotion of food sources of active cultures creates a similar dilemma. Food sources of active cultures (FSAC) include fermented meats, vegetables, legumes, grains, and even cultured dairy products. Foods such as yogurt, kefir, kimchi, sauerkraut, and even sourdough are all classified as FSAC’s. Fermentation has long been used as a method to preserve foods prior to modern refrigeration. The fermentation process would allow foods to be shelf-stable for long periods of time, whereas now, these methods are more commonly used to improve the health properties of foods. However, not all fermented foods contain live cultures and microorganisms [4]. Many of the products we consume such as beer, wine, sausages, and even fermented vegetables are heat-treated during processing to remove any unwanted pathogens. This process kills many of the beneficial bacteria. FSAC’s are not required to inform the customer of specific genus, species, or strains in their product. Moreover, those foods may not even contain the specific strains that provides health benefits to the consumer. While the final food product may still have potential health benefits, it may only come from the enhancement of the food during fermentation, rather than the bacterial profile itself [6].
While probiotics, prebiotics, and FSAC’s should be part of a healthy diet, and can create many health benefits for those that consume them, the market is currently flooded with these products being touted as “cure-all’s” for most common ailments. While the statement may contain some validity, that these compounds can improve or even cure those conditions, most supplements due not contain the proper species, strains, or dosages to create such change. Therefore, it would be far more beneficial to research particular conditions or ailments, and find the appropriate strains, rather than spending hundreds, if not thousands of dollars on “generic” supplements, hoping they will improve your health. Therefore, taking an individualized approach to health is fundamental for success.
References:
1. Cooper, T. E., Cooper, T. E., Khalid, R., Craig, J. C., Hawley, C. M., Howell, M., Johnson, D. W., Teixeira-Pinto, A., Tong, A., & Wong, G. (n.d.). Synbiotics, prebiotics and probiotics for people with chronic kidney disease. Cochrane Database of Systematic Reviews, 5.
2. Marx, W., Scholey, A., Firth, J., D’Cunha, N. M., Lane, M., Hockey, M., Ashton, M. M., Cryan, J. F., O’Neil, A., Naumovski, N., Berk, M., Dean, O. M., & Jacka, F. (2020). Prebiotics, probiotics, fermented foods and cognitive outcomes: A meta-analysis of randomized controlled trials. Neuroscience and Biobehavioral Reviews, 118, 472–484.
3. McFarland, L. V., Evans, C. T., & Goldstein, E. J. C. (2018). Strain-Specificity and Disease-Specificity of Probiotic Efficacy: A Systematic Review and Meta-Analysis. Frontiers in Medicine. https://doi-org.uws.idm.oclc.org/10.3389/fmed.2018.00124.
4. Melini, F., Melini, V., Luziatelli, F., Ficca, A. G., & Ruzzi, M. (2019). Health-Promoting Components in Fermented Foods: An Up-to-Date Systematic Review. Nutrients, 11(5). https://doi-org.uws.idm.oclc.org/10.3390/nu11051189.
5. Mugambi, M. N., Young, T., & Blaauw, R. (2014). Application of evidence on probiotics, prebiotics and synbiotics by food industry: A descriptive study. BMC Research Notes, 7(1). doi:10.1186/1756-0500-7-754.
6. Rezac, S., Kok, C. R., Heermann, M., & Hutkins, R. (2018). Fermented Foods as a Dietary Source of Live Organisms. Frontiers in Microbiology. https://doi-org.uws.idm.oclc.org/10.3389/fmicb.2018.01785.
7. Saif Ul Islam, & Islam, S. U. (2016). Clinical Uses of Probiotics. Medicine, 95(5), 1–5. https://doi-org.uws.idm.oclc.org/10.1097/MD.0000000000002658.
8. Wampach, L., Heintz-Buschart, A., Fritz, J.V. et al. Birth mode is associated with earliest strain-conferred gut microbiome functions and immunostimulatory potential. Nat Commun 9, 5091 (2018). https://doi.org/10.1038/s41467-018-07631-x
9. Zhu, B., Wang, X. & Li, L. Human gut microbiome: the second genome of human body. Protein Cell 1, 718–725 (2010). https://doi.org/10.1007/s13238-010-0093-z.