The Benefits of Probiotics

You’ve likely heard of the buzzwords “probiotics” or “microbiome.” Talk about gut health and gut bacteria are saturating the health and nutrition spheres. They’re even appearing on the covers of magazines and the shelves of supplement sections in health food stores. So, what are probiotics?

Probiotics are "live microorganisms, which when administered in adequate amounts, confer a health benefit on the host" [1].

Here are a few of the benefits:

1. Probiotics Can Improve Digestive Health

Intestines: decade3d/Fotolia

The majority of the bacteria that constitute our gut microbiome exist in the large intestines.

When there is an imbalance in the distribution of bacteria in our guts, known as dysbiosis, “bad” bacteria can contribute to a host of digestive issues such as irritable bowel syndrome (IBS), autoimmune and allergic diseases, obesity, diabetes, and inflammatory bowel disease [2].

Dysbiosis can be caused by poor diet, exposure to environmental toxins, pathogens, or drugs such as antibiotics [3].

When “good” probiotic gut bacteria are dominant, they can combat the issues that arise from intestinal disorders such as constipation, gas and bloating, fatigue, food intolerance, frequent stools, nausea, and abdominal pain [4]. These are symptoms of IBS, which is one of the leading causes of workplace absenteeism [5].

The usage of probiotics to treat inflammatory bowel diseases, such as ulcerative colitis and Crohn’s disease, has also shown promise [6] [7].

2. Probiotics Can Aid Digestion & Absorption

Sourdough Starter: BBC Food

Probiotics in fermented foods can aid in the breakdown of components that can be difficult to digest.

Milk, for example, contains lactose. When fermented, the metabolic processes of certain bacteria (ie. Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus) break down the lactose in milk, turning the milk into yogurt. This makes it more easily digestible, especially for those who are lactose intolerant [8].

Gluten is another compound that causes digestive discomfort in certain people. It is a type of lectin, a category of proteins found in many plants that developed as part of a plant’s chemical defense [9]. Common food sources that contain lectins are whole grains and legumes.

In addition to causing digestive discomfort, lectins can interfere with the absorption of minerals such as calcium, iron, phosphorus, and zinc [10], as well as disrupt hormone and immunological function, and damage gut cells [11].

Certain types of bacteria have the ability to digest and break down gluten [12] and other compounds in wheat that cause digestive discomfort [13] [14].

These types of bacteria are present in sourdough bread, a traditional bread that can be made with just four ingredients: flour, water, salt, and a starter culture. The sourdough starter contains the microbes that break down and digest components of wheat (ie. gluten) that adversely affect those who can’t tolerate most forms of modern bread. Research indicates that sourdough bread may be a viable solution for those sensitive or intolerant to gluten [15].

In addition to providing digestive support by breaking down compounds that we may be unable to digest efficiently, specific types of bacteria also appear to aid micronutrient absorption by increasing bioavailability [16].

3. Probiotics May Positively Impact Mental Health

Brain: PhysicsWorld

Gut bacteria play a significant role in the production and balance of serotonin in the gut [17] which is the cite of over 90% of our serotonin production. Serotonin is commonly known as one of the “happy chemicals,” but its function is broader than its impact on brain chemistry. Serotonin is a major neurotransmitter in the body used for neuron-to-neuron signaling all over the body, regulating various biological processes such as cardiovascular function and bladder control [18].

Research has supported the notion that microbiota in the gut have a measurable impact on both brain chemistry and behavior [19]. This link is also reflected in the frequent presence of depression and anxiety in individuals that also experience IBS.

Some scientists attribute this to the interactions between microbiota and the gut-brain axis (GBA) [20], a link between the central and the enteric nervous systems. The enteric nervous system encompasses the gastrointestinal tract. This intricate network of neurons is so expansive it’s been nicknamed the “second brain” in reference to its significance.

Probiotics have been shown to reduce anxiety and depressive symptoms in animal models [21], and the role of gut microbiota in modulating anxiety has been demonstrated [22]. These studies suggest that the targeting of the microbiome could potentially be an effective approach to address mental health.

4. Probiotics May Improve Immunity

Flu: Getty Images

Interactions between the host and microorganisms, both harmful and beneficial, primarily occur in the gastrointestinal tract. This makes the mucosal lining in the gut a major line of defense against pathogens, harmful toxins, and allergens.

Probiotics are shown to both aid in the maintenance of healthy gut mucosa function and the enhancement of barrier function through the synthesis, assembly, and protection of tight junction proteins which prevent the passage of unwanted particles [23]. Research indicates that the state and composition of the microbiome are significant factors in the determination of immune response strength [24].

When the gut is in a state of dysbiosis, individuals seem to be much more prone to developing autoimmune, allergic, and inflammatory disorders [25].

In addition to the strengthening of the gut lining and immune response, there is some evidence that probiotics can prevent acute conditions such as upper respiratory tract infections [26].

5. Probiotics Impact Metabolic Health

Metabolism: Getty Images

There is an epidemic of metabolic diseases in the developed world. As the Western lifestyle has spread to various developing nations, the epidemic of metabolic diseases has established itself on a global scale [27].

Metabolic diseases, such as obesity and type II diabetes, are characterized by the improper functioning of metabolic processes. A key dysfunction in metabolic disease is insulin resistance, which is the gradual desensitization to insulin often due to continuous overexposure [28].

Since an altered gut microbiome is associated with various metabolic diseases, the usage of probiotics to improve the distribution of gut microbiota could counter these diseases [29]. In fact, researchers have found that in individuals with metabolic syndrome, insulin sensitivity increased with positive alterations in intestinal microbiota [30]. This means that a healthy gut microbiome distribution may help combat insulin resistance-- a hallmark of metabolic disease.

Microbes in the gut impact processes from inflammation and insulin resistance to the deposition of energy in fat stores; this, along with the correlation between an altered microbiome and obesity, leads researchers to believe that the restoration of healthy gut bacteria may even be able to combat obesity directly and aid in the maintenance of a healthy weight [31].

The tiny microbes in our microbiomes have a large impact on our health. They play key roles in optimizing digestion, providing protection, supporting immunological function, and regulating processes that affect both mental and metabolic health. The correlations between dysbiosis and various diseases and disorders have been established, but the efficacy of probiotic usage to address these issues is still questionable.

Generally, the therapeutic usage of probiotics aims to positively influence the distribution of the gut microbiome, shifting it out of dysbiosis. The strong correlations between dysbiosis and disease indicate that this positive shift would also reduce disease. The hardship lies in the capability of supplemented probiotic bacteria to take root in the gut [32]. Only after integration with the existing environment can the state of the microbiome be influenced by these new strains of beneficial bacteria.

Still, there is great potential for the therapeutic usage of probiotics. The study of the human gut and probiotics is a fascinating, ongoing area of research.

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What are your thoughts?

Elle Lee

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References

1. Hill, C. et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat. Rev. Gastroenterol. Hepatol. 11, 506–514 (2014).

2. Clemente, J. C., Ursell, L. K., Parfrey, L. W., & Knight, R. (2012). The impact of the gut microbiota on human health: an integrative view. Cell, 148(6), 1258–1270. doi:10.1016/j.cell.2012.01.035

3. Carding, S., Verbeke, K., Vipond, D. T., Corfe, B. M., & Owen, L. J. (2015). Dysbiosis of the gut microbiota in disease. Microbial ecology in health and disease, 26, 26191. doi:10.3402/mehd.v26.26191

4. Moayyedi P, Ford AC, Talley NJ, et al. The efficacy of probiotics in the treatment of irritable bowel syndrome: a systematic review. Gut 2010;59:325-332.

5. The Costly Toll of IBS. (2016, November 30). Retrieved from https://badgut.org/information-centre/a-z-digestive-topics/the-costly-toll-of-ibs/.

6. Jonkers, D., Penders, J., Masclee, A. et al. Drugs (2012) 72: 803. https://doi.org/10.2165/11632710-000000000-00000

7. Sokol, H., Pigneur, B., Watterlot, L., Lakhdari, O., Bermúdez-Humarán, L. G., Gratadoux, J. J., … Langella, P. (2008). Faecalibacterium prausnitzii is an anti-inflammatory commensal bacterium identified by gut microbiota analysis of Crohn disease patients. Proceedings of the National Academy of Sciences of the United States of America, 105(43), 16731–16736. doi:10.1073/pnas.0804812105

8. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA); Scientific Opinion on the substantiation of health claims related to live yoghurt cultures and improved lactose digestion (ID 1143, 2976) pursuant to Article 13(1) of Regulation (EC) No 1924/2006. EFSA Journal 2010; 8( 10):1763. [18 pp.]. doi:10.2903/j.efsa.2010.1763

9. Gundry, S.R. (2017). The Plant Paradox: The Hidden Dangers in "Healthy" Foods That Cause Disease and Weight Gain. Harper Wave.

10. Are anti-nutrients harmful? (2019, October 21). Retrieved from https://www.hsph.harvard.edu/nutritionsource/anti-nutrients/.

11. Ilka M Vasconcelos, José Tadeu A Oliveira. (2004). Antinutritional properties of plant lectins. Toxicon, Volume 44, Issue 4, 385-403. https://doi.org/10.1016/j.toxicon.2004.05.005.

12. Carla Luciana Gerez, Andrea Dallagnol, Graciela Rollán, Graciela Font de Valdez. (2012). A combination of two lactic acid bacteria improves the hydrolysis of gliadin during wheat dough fermentation. Food Microbiology, Volume 32, Issue 2, 427-430, ISSN 0740-0020. https://doi.org/10.1016/j.fm.2012.06.007.

13. Jessica R. Biesiekierski, Simone L. Peters, Evan D. Newnham, Ourania Rosella, Jane G. Muir, Peter R. Gibson. (2013). No Effects of Gluten in Patients With Self-Reported Non-Celiac Gluten Sensitivity After Dietary Reduction of Fermentable, Poorly Absorbed, Short-Chain Carbohydrates. Gastroenterology, Volume 145, Issue 2. 320-328.e3. ISSN 0016-5085. https://doi.org/10.1053/j.gastro.2013.04.051.

14. J.G. Muir, J.E. Varney, M. Ajamian, P.R. Gibson. Gluten-free and low-FODMAP sourdoughs for patients with coeliac disease and irritable bowel syndrome: A clinical perspective. (2019). International Journal of Food Microbiology, Volume 290. 237-246. ISSN 0168-1605, https://doi.org/10.1016/j.ijfoodmicro.2018.10.016.

15. Cagno, R. D., Angelis, M. D., Auricchio, S., Greco, L., Clarke, C., Vincenzi, M. D., … Gobbetti, M. (2004, February 1). Sourdough Bread Made from Wheat and Nontoxic Flours and Started with Selected Lactobacilli Is Tolerated in Celiac Sprue Patients. Retrieved from https://aem.asm.org/content/70/2/1088#sec-15.

16. Sheridan, P. O., Bindels, L. B., Saulnier, D. M., Reid, G., Nova, E., Holmgren, K., … Scott, K. P. (2014). Can prebiotics and probiotics improve therapeutic outcomes for undernourished individuals?. Gut microbes, 5(1), 74–82. doi:10.4161/gmic.27252

17. Reigstad, C. S., Salmonson, C. E., Rainey, J. F., 3rd, Szurszewski, J. H., Linden, D. R., Sonnenburg, J. L., … Kashyap, P. C. (2015). Gut microbes promote colonic serotonin production through an effect of short-chain fatty acids on enterochromaffin cells. FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 29(4), 1395–1403. doi:10.1096/fj.14-259598

18. Berger, M., Gray, J. A., & Roth, B. L. (2009). The expanded biology of serotonin. Annual review of medicine, 60, 355–366. doi:10.1146/annurev.med.60.042307.110802

19. Dinan, T. G., & Cryan, J. F. (2013, August 1). Melancholic microbes: a link between gut microbiota and depression? Retrieved from https://onlinelibrary.wiley.com/doi/full/10.1111/nmo.12198

20. Carabotti, M., Scirocco, A., Maselli, M. A., & Severi, C. (2015). The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Annals of gastroenterology, 28(2), 203–209.

21. Anastasiya Slyepchenko, Andre F. Carvalho, Danielle S. Cha, Siegfried Kasper and Roger S. McIntyre. (2014). Gut Emotions - Mechanisms of Action of Probiotics as Novel Therapeutic Targets for Depression and Anxiety Disorders. CNS & Neurological Disorders - Drug Targets.13: 1770. https://doi.org/10.2174/1871527313666141130205242

22. Hoban1, A. E., Stilling1, R. M., Moloney2, G. M., Moloney1, R. D., Shanahan1, F., Dinan1, T. G., … Clarke1, G. (2017, August 25). Microbial regulation of microRNA expression in the amygdala and prefrontal cortex. Retrieved from https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-017-0321-3

23. Rao, R. K., & Samak, G. (2013). Protection and Restitution of Gut Barrier by Probiotics: Nutritional and Clinical Implications. Current nutrition and food science, 9(2), 99–107.

24. Honda, K., & Littman, D. R. (2012). The microbiome in infectious disease and inflammation. Annual review of immunology, 30, 759–795. doi:10.1146/annurev-immunol-020711-074937

25. Honda, K., & Littman, D. R. (2012). The microbiome in infectious disease and inflammation. Annual review of immunology, 30, 759–795. doi:10.1146/annurev-immunol-020711-074937

26. Hao  Q, Dong  BR, Wu  T. Probiotics for preventing acute upper respiratory tract infections. Cochrane Database of Systematic Reviews 2015, Issue 2. Art. No.: CD006895. DOI: 10.1002/14651858.CD006895.pub3.

27. Saklayen M. G. (2018). The Global Epidemic of the Metabolic Syndrome. Current hypertension reports, 20(2), 12. doi:10.1007/s11906-018-0812-z

28. R.SinaikoMD1, A. (2012, February 14). Insulin Resistance. Retrieved from https://www.sciencedirect.com/science/article/pii/S0022347612000315.

29. Joyce, S. A., & Gahan, C. G. M. (2014, March). The gut microbiota and the metabolic health of the host. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/24468803?dopt=Abstract&holding=npg.

30. Vrieze, Anne et al. (2012, June 20). Transfer of Intestinal Microbiota From Lean Donors Increases Insulin Sensitivity in Individuals With Metabolic Syndrome. Retrieved from https://www.sciencedirect.com/science/article/abs/pii/S001650851200892X.

31. Ley, R. E. (2010, January). Obesity and the human microbiome. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/19901833.

32. Human gut study questions probiotic health benefits. (2018, September 6). Retrieved from https://www.sciencedaily.com/releases/2018/09/180906141640.htm.

Cover Image. Illustration by Marcia Staimer, www2.gmu.edu/news/188421