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How Probiotics Boost Immunity

Article at-a-glance:

  • The immune system becomes more vulnerable to infection and inflammation as we age
  • Studies show probiotics protect against infections
  • Species of probiotics have been studied for many conditions, including IBS and to fight infections
  • Some probiotics stimulate the secretion of an immune protein that helps protect against pathogens, as well as promote a healthy allergic response, modulate the expression of genes and release important natural enzymes
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Probiotics are healthy gut bacteria with a wide-range of health benefits, including boosting immunity, balancing inflammation and fighting infections. The average human provides a home to about 100 trillion microbes, the majority of which make their living in your gut.1 The gut is one of the most densely populated ecosystems on the planet. With so many of them, it’s not surprising that they do a lot of work. Some microbes help break down foods and synthesize vitamins. For example, intestinal probiotics synthesize B vitamins,2 help keep inflammation in check3 and a healthy gut microbiome is associated with higher levels of vitamin D.4 A healthy, plant-based diet and time-restricted eating, also called intermittent fasting, have been shown to change the microbiome, making it healthier and increasing the diversity of organisms.5

Microbiome health

When an imbalance between friendly and unfriendly organisms develops, you get intestinal dysbiosis. When these unhealthy critters dominate, we are more susceptible to unhealthy amounts of inflammation, gastrointestinal distress, blood sugar imbalance, difficulty managing weight, infections and feeling blue.6

Our probiotics need nutrients to grow and sustain themselves. This includes certain carbohydrates and fibers that we can’t digest, but our friendly bacteria love. Giving them what they need to be healthy helps us be healthy too. Two groups of important prebiotics are fructooligosaccharides (FOS) and galactooligosaccharides (GOS).7 Prebiotics are frequently found in vegetables, which is why Belly Rescue includes a prebiotic blend from plants, such as Jerusalem artichoke and chicory root. 

As we get older, dysbiosis becomes more common. That’s because medications, diet, stress, and environmental toxins can kill healthy gut bacteria.8 Antibiotics indiscriminately kill good and bad bacteria. When the balance between healthy and unhealthy bacteria gets disturbed, it provides an opportunity for disease-causing species to multiply and create problems. And if you’ve been prescribed multiple rounds of antibiotics, your risk for dysbiosis increases even more.9 Along with antibiotics, acid-blocking medications (eg, Protonix, Prilosec), non-steroidal anti-inflammatories (eg, Tylenol, acetaminophen, Ibuprofen), antipsychotic medications and metformin have also been shown to create dysbiosis and are some of the most common gut killers.10,11


Older adults are at higher risk for infections, and they die three times as often from infections compared to younger adults. For example, during the flu season, about 90% of flu-related deaths occur in people older than 65.12 Flu vaccines are also not as potent in the elderly.13 Additionally, as people get older the immune system tilts towards inflammation, contributing to unhealthy blood clotting and the illnesses that are so common we age—cancer, cardiovascular disease, stroke, arthritis, osteoporosis, and dementia.14 

Fortunately, there are many ways you can support your immune system and combat “inflammaging.” As the name implies, inflammaging is a chronic, low-grade inflammation that ages you faster. It contributes to osteoporosis, arthritis, heart disease, losing brain cells, and seeing more lines and wrinkles staring back at you in the mirror by destroying collagen. The first step is making sure you’re following a whole foods diet, getting enough sleep, and reducing stress, which is all part of the four pillars of health

Supplementing with a pre- and pro-biotic blend can also help. Probiotics can suppress pathogens. In fact, molecules secreted by friendly lactic-acid probiotics can reduce the prevalence and virulence of certain highly inflammatory bacteria such as Klebsiella and E. coli.15 A molecule secreted by the probiotic Lactobacillus salivarius prevents mice from succumbing to invasive infections caused by Listeria monocytogenes.16 

Probiotics can also help counter the negative effect of antibiotics, including diarrhea. A review of scientific literature on probiotics and GI disorders by the American Gastroenterological Association (AGA) Institute found that may be helpful in reducing the risk fo CDAD (C. difficile associated diarrhea) after antibiotic use.”17

Streptococcus thermophilus, a naturally occurring probiotic, exerts antimicrobial activity by virtue of its production of lactic acid and antibacterial peptides called thermophilins. These can inhibit or kill bacteria. The lactic acid produced by S. thermophilus may reduce pathogen growth. In mice infected with C. difficile, giving them S. thermophilus resulted in 46% less weight loss as compared with mice not taking the probiotic. Taking S. thermophilus was associated with less diarrhea, lower pathology scores, and a decrease in C. difficile toxin production.18 In vitro studies have shown that thermophilins can inhibit many opportunistic and foodborne pathogens, including Enterococcus faecalis, Staphylococcus aureus, Clostridium botulinum, and Listeria monocytogenes.19.20,21,22

Probiotics also support a healthy immune system by stimulating the body’s secretion of immunoglobulin A (IgA). This immune protein helps protect against gastrointestinal infections, as well as reduce allergies, modulate the expression of genes, release important natural enzymes and decrease the ability of pathogens to adhere to the intestinal wall.23

Probiotics have even been demonstrated to improve vaccine response in adults. A review of twenty randomized controlled trials in nearly 2000 adults who took probiotics or prebiotics found the response to flu vaccine was significantly improved over their counterparts who did not consume probiotics and prebiotics.24 In other research on probiotics and response to vaccines, B. bifidum and L. acidophillus increased the response to the gut pathogen Salmonella typhi.25 

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1BEC Crew. Here’s How Many Cells in Your Body Aren’t Actually Human. April 2018. [Report]

2Yoshii K, Hosomi K, Sawane K, Kunisawa J. Metabolism of Dietary and Microbial Vitamin B Family in the Regulation of Host Immunity. Front Nutr. 2019;6:48. [Article]

3Wang J, Chen WD, Wang YD. The Relationship Between Gut Microbiota and Inflammatory Diseases: The Role of Macrophages. Front Microbiol. 2020;11:1065. [Article]

4Active Vitamin D Levels Linked to Gut Microbiome. Genetic Engineering & Biotechnology News. Accessed June 2021. [Report]

5Zarrinpar A, Chaix A, Yooseph S, Panda S. Diet and feeding pattern affect the diurnal dynamics of the gut microbiome. Cell Metab. 2014;20(6):1006-1017. [Article]

6Wilkins LJ, Monga M, Miller AW. Defining Dysbiosis for a Cluster of Chronic Diseases. Sci Rep. 2019;9(1):12918. Published 2019 Sep 9. [Article]

7Davani-Davari D, Negahdaripour M, Karimzadeh I, et al. Prebiotics: Definition, Types, Sources, Mechanisms, and Clinical Applications. Foods. 2019;8(3):92. [Article]

8Karl JP, Hatch AM, Arcidiacono SM, et al. Effects of Psychological, Environmental and Physical Stressors on the Gut Microbiota. Front Microbiol. 2018;9:2013. [Article]

9Konstantinidis T, Tsigalou C, Karvelas A, Stavropoulou E, Voidarou C, Bezirtzoglou E. Effects of Antibiotics upon the Gut Microbiome: A Review of the Literature. Biomedicines. 2020;8(11). [Article]

10Clooney AG, Bernstein CN, Leslie WD, et al. A comparison of the gut microbiome between long-term users and non-users of proton pump inhibitors. Aliment Pharmacol Ther. 2016;43(9):974-984. [Article]

11Le Bastard Q, Al-Ghalith GA, Grégoire M, et al. Systematic review: human gut dysbiosis induced by non-antibiotic prescription medications. Aliment Pharmacol Ther. 2018;47(3):332-345. [Article]

12 Statista. Number of deaths due to influenza during the 2018-2019 flu season in the United States, by age group. Accessed June 2012. [Report

13Jiang N et al. 2013 Lineage structure of the human antibody repertoire in response to influenza vaccination. Sci. Transl. Med. 5, 171ra19. [Article]

14Simon AK, Hollander GA, McMichael A. Evolution of the immune system in humans from infancy to old age. Proc Biol Sci. 2015 Dec 22;282(1821):20143085 [Article]

15Adeniyi BA, Adetoye A, Ayeni FA. Antibacterial activities of lactic acid bacteria isolated from cow faeces against potential enteric pathogens. Afr Health Sci. 2015;15(3):888-895. [Article]

16Corr SC, Li Y, Riedel CU, O’Toole PW et al. Bacteriocin production as a mechanism for the antiinfective activity of Lactobacillus salivarius UCC118. Proc Natl Acad Sci U S A. 2007;104(18):7617-7621. [Article]

17Preidis GA, Weizman AV, Kashyap PC, Morgan RL. AGA Technical Review on the Role of Probiotics in the Management of Gastrointestinal Disorders. Gastroenterology. 2020 Aug;159(2):708-738.e4 [Article]

18Kolling GL, Wu M, Warren CA, et al. Lactic acid production by Streptococcus thermophilus alters Clostridium difficile infection and in vitro Toxin A production. Gut Microbes. 2012;3(6):523-529. [Article]

19Fontaine L, Hols P. The inhibitory spectrum of thermophilin 9 from Streptococcus thermophilus LMD-9 depends on the production of multiple peptides and the activity of BlpG(St), a thiol-disulfide oxidase. Appl Environ Microbiol. 2008;74(4):1102-1110. [Article]

20Rossi F, Marzotto M, Cremonese S, Rizzotti L, Torriani S. Diversity of Streptococcus thermophilus in bacteriocin production; inhibitory spectrum and occurrence of thermophilin genes. Food Microbiol. 2013;35(1):27-33. [Article]

21Kabuki T, Uenishi H, Watanabe M, Seto Y, Nakajima H. Characterization of a bacteriocin, Thermophilin 1277, produced by Streptococcus thermophilus SBT1277. J Appl Microbiol. 2007;102(4):971-980. [Article]

22Gilbreth SE, Somkuti GA. Thermophilin 110: a bacteriocin of Streptococcus thermophilus ST110. Curr Microbiol. 2005;51(3):175-182. [Article]

23Plaza-Diaz J., Ruiz-Ojeda F.J., Gil-Campos M et al. Mechanisms of action of probiotics. Adv. Nutr. 2019;10:S49–S66. [Article]

24Lei WT, Shih PC, Liu SJ etal. Effect of Probiotics and Prebiotics on Immune Response to Influenza Vaccination in Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients. 2017 Oct 27;9(11):1175. [Article]

25Vitetta L., Saltzman E.T., Thomsen M. et al. Adjuvant probiotics and the intestinal microbiome: Enhancing vaccines and immunotherapy outcomes. Vaccines. 2017;5:50. [Article]

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