Probiotics for immune system

When it comes to whole body health, a lot of parts vie for the spotlight—your brain, your heart, you name it. But since your gut microbiome accounts for a whopping 70%1 of your immune system, what happens inside this community of microbes, also called microbiota, can dictate much of what happens to you from head to toe, even how well you sleep2. And while research is still evolving, there’s even evidence showing that your gut could play a role in viral infections such as SARS-CoV-2, or COVID-193.

Let’s break it down.

What is the Gut Microbiome?

This ecosystem in your digestive tract is made up of more than 100 trillion bacteria spanning more than 1,000 species4. But you didn’t start with that much diversity. As a fetus, the microbiome is a blank slate5. Passing through the birth canal is your first exposure to bacteria and breastfeeding results in more microbes. When you hit age 3, you essentially have an adult microbiome6.

As years pass, factors like diet, antibiotic use, and lifestyle can affect the composition of your microbiome. Do you take probiotics and eat probiotic-rich foods like live culture yogurt? Are you a non-smoker7? Do you manage your stress levels? These are all ways to keep your microbiome in tip-top shape.

How a Healthy Gut Microbiome Influences Immunity

Your microbiome plays several important roles, from synthesizing vitamins and breaking down complex carbs to informing the immune system on how best to function8. The actual communication between your gut and your immune system is a dialogue among epithelial cells, mucus, Immunoglobulin A, antimicrobial peptides, and immune cells that all band together to create a sort-of firewall5. Basically, keep in the good and keep out the bad to achieve equilibrium.

That’s why feeding your gut with the highest quality probiotics strains—like Bifidobacterium lactis Bl-04 which you can find in Routine For Her and has been shown to improve immune response time9—is paramount to protecting your body against possible infections and cutting down just how long you’ll be sick, too. In one scientific review, kids and adults who took a probiotic supplement had “significantly fewer numbers of days of illness” and were absent from work or school less than those who took a placebo10.

The Benefits to Your Respiratory Health

Depending on the strain, probiotics have been clinically proven to help regulate the effects of viral infections, allergies, and other immune response-related diseases11.

For Routine, we chose Bifidobacterium lactis Bl-04 specifically because the research is aplenty, including evidence that Bl-04 can help significantly reduce the risk of upper respiratory tract infections by 27%. Need more numbers? While the median time for the placebo group to get sick was 2.5 months, the median for those who took Bl-04 wasn’t until the 3.2-month mark12.

And not all Bifidobacteria are created equally. In the same study, when comparing Bifidobacterium lactis Bl-04 to Bifidobacterium lactis Bi-07, and a placebo, researchers found that the risk of getting an upper respiratory illness was lower in the Bl-04 group.

Probiotics and COVID-19

Research is in early stages, but experts have seen potential for probiotics to positively influence  viral infections like COVID-19. Spread of the highly contagious virus typically occurs through respiratory droplets—like when someone coughs or sneezes—but the FDA reported that COVID-19 RNA was found in patients’ stool samples as well13. Other reports state a demonstrated link between COVID-19 and intestinal imbalance, explaining that the inflammation from the microbiome can result in a poor response to pathogens. Essentially, your body isn’t in fighting condition when it really needs to be, and your gut plays a role in that.

That’s where probiotics have potential to help. In a May 2020 report in the peer-reviewed journal Frontiers, researchers stated a case for taking the daily capsules, citing not just probiotics’ ability to help restore balance in the gut microbiome, but also the established connection between the microbiomes in your gut and lungs3. In particular, certain probiotic strains have the potential to minimize “immune response-mediated damage to the lungs”—a potential breakthrough to treat acute respiratory distress syndrome (ARDS), which is a frequent complication of COVID-19.

It’s important to note that the science is still emerging, with new reports and data being analyzed (and re-analyzed) every day. But given the significant evidence that certain probiotic strains can help reduce the frequency and severity of upper respiratory infections and an already demonstrated correlation to boosted immunity, there’s serious potential. As we say, what happens in the gut doesn’t stay in the gut—it can have implications for the whole body.

The Takeaway

Keeping our microbiomes in shape can be a useful tool while we all navigate our new normal. Beyond taking a daily probiotic, there are other things you can do to stay healthy and make your immune systems as robust as possible. Get enough sleep. Eat a balanced, whole food-centric diet. Exercise regularly. And yes, wash your hands for at least 20 seconds. Ultimately, it comes down to supporting your body from all angles so you can be the best, most healthy version of yourself every day.

To learn more about the research behind Routine, check out The Science, our deep-dive into the clinical trials and scientific studies that helped us select the most effective, premium strains for Routine.


 1 Nagano T, Otoshi T, Hazama D, et al. Novel cancer therapy targeting microbiome. Onco Targets Ther. 2019;12:3619-3624. doi:10.2147/OTT.S207546
2 Smith RP, Easson C, Lyle SM, et al. Gut microbiome diversity is associated with sleep physiology in humans. PLoS ONE. 2019;14(10):e0222394. doi: 10.1371/journal.pone.0222394
3 Baud D, Dimopoulou Agri V, Gibson G, Reid G, Giannoni E. Using probiotics to flatten the curve of coronavirus disease COVID-2019 pandemic. Front Public Health. 2020;8. doi:10.3389/fpubh.2020.00186
4 Shreiner AB, Kao JY, Young VB. The gut microbiome in health and in disease. Curr Opin Gastroenterol. 2015;31(1):69-75. doi:10.1097/MOG.0000000000000139
5 Belkaid Y, Hand TW. Role of the microbiota in immunity and inflammation. Cell. 2014;157(1):121-41. doi:10.1016/j.cell.2014.03.011
6 Hasan N, Yang H. Factors affecting the composition of the gut microbiota, and its modulation. PeerJ. 2019;7:e7502. doi:10.7717/peerj.7502
7 Savin Z, Kivity S, Yonath H, Yehuda S. Smoking and the intestinal microbiome. Arch Microbiol. 2018;200(5):677-684. doi:10.1007/s00203-018-1506-2
8 The Microbiome. Harvard T.H. Chan School of Public Health.
9 Paineau D, Carcano D, Leyer G, et al. Effects of seven potential probiotic strains on specific immune responses in healthy adults: a double-blind, randomized, controlled trial. FEMS Immunol Med Microbiol. 2008;53(1):107-13. doi:10.1111/j.1574-695X.2008.00413.x
10 King S, Glanville J, Sanders ME, Fitzgerald A, Varley D. Effectiveness of probiotics on the duration of illness in healthy children and adults who develop common acute respiratory infectious conditions: a systematic review and meta-analysis. Br J Nutr. 2014;112(1):41-54. doi:10.1017/S0007114514000075
11 Yan F, Polk DB. Probiotics and immune health. Curr Opin Gastroenterol. 2011;27(6):496-501. doi:10.1097/MOG.0b013e32834baa4d
12 West NP, Horn PL, Pyne DB, et al. Probiotic supplementation for respiratory and gastrointestinal illness symptoms in healthy physically active individuals. Clin Nutr. 2014;33(4):581-7. doi:10.1016/j.clnu.2013.10.002
13 Fecal microbiota for transplantation: safety alert - regarding additional safety protections pertaining to SARS-CoV-2 and COVID-19. U.S. Food & Drug Administration. 2020.


  • What specific lifestyle changes besides diet and probiotic use can affect the gut microbiome?

    Lifestyle changes beyond diet and probiotic use that can influence the gut microbiome include factors such as regular exercise habits, exposure to environmental toxins, medication usage (particularly antibiotics and certain medications that can affect gut health), and even psychological stress levels. These factors can all impact the diversity and composition of the microbiome, influencing its ability to support overall health and immunity.

  • Are there any potential side effects or risks associated with taking probiotics for immune support?

    While probiotics are generally considered safe for most people, there can be potential side effects for some individuals, such as gastrointestinal discomfort, bloating, or allergic reactions. Additionally, there may be risks associated with probiotic use in certain populations, such as people with compromised immune systems or underlying health conditions. It's important for individuals considering probiotic supplementation to consult with a healthcare professional, especially if they have any concerns or existing health conditions.

  • How do probiotics specifically interact with the immune system to improve response time and reduce illness duration?

    Probiotics interact with the immune system through various mechanisms, including modulating the balance of gut bacteria, enhancing the production of immune-regulating molecules, and supporting the function of immune cells. Specific strains of probiotics, like Bifidobacterium lactis Bl-04 mentioned in the article, have been shown in research to improve immune response time and reduce illness duration by supporting a healthy immune system. However, the exact mechanisms behind these effects may vary depending on the probiotic strain and individual factors, and further research is needed to fully understand their interactions with the immune system.


Written by Philippe Gauthier

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