Could L. reuteri Be the Key to Fewer Sick Days?

Let's be honest: this flu season has been brutal. If you've been battling wave after wave of illness, constantly worried about the next bug that will knock you (or your kids) out for days, you're not alone. This feels like one of the worst flu seasons we've seen in decades.

This Year's Flu Season: The Numbers Don't Lie

According to the latest data from the CDC, over 24 million Americans have already fallen ill with the flu this season, resulting in more than 310,000 hospitalizations and over 20,000 deaths.¹ For families, the impact can be devastating. Missed school days pile up. Work deadlines get pushed back. That family trip you planned is postponed. You burn through your PTO. The emotional and financial toll of repeat illness goes far beyond just feeling under the weather.

What You Can Do: Focus on Improving Your Immune Function

Fun Fact: Approximately 70% of your immune cells actually live in your gut,² with the gut playing a central role in your body's overall immune distribution.³ Your digestive system isn't just responsible for breaking down last night's dinner. It's a central hub for your body's immune function.

But here's the problem. Modern life has left most of us with depleted gut microbiomes. Stress, processed foods, antibiotics, pollution - they've all taken a toll on the beneficial bacteria we are born with that help support our immune systems. Research shows that L. reuteri (Limosilactobacillus reuteri), a keystone bacterial species our ancestors had in abundance, has nearly disappeared from the gut microbiomes of most Western people.⁴˒⁵

Meet Your Gut's Immune-Supporting Allies: L. reuteri ATCC PTA 6475 and DSM 17938

Not all probiotics are created equal, and when it comes to supporting immune function and helping maintain a healthy inflammatory response, two specific strains of L. reuteri stand out: ATCC PTA 6475 and DSM 17938. These aren't just random bacterial strains; they're scientifically studied keystone bacteria that have been extensively researched for their potential to support immune health and gut barrier function.

If you're wondering how your gut microbiome changes as it moves toward balance with these keystone bacteria, you can learn more about the timeline of gut healing and what to expect.

How L. reuteri ATCC PTA 6475 May Help Support a Healthy Inflammatory Response

Inflammation is your body's alarm system. It can be helpful in short bursts, but when it becomes chronic, it can affect overall wellness in many different ways. L. reuteri ATCC PTA 6475 has been studied for its potential to support a healthy inflammatory response.

Research published in the American Journal of Physiology-Gastrointestinal and Liver Physiology showed that this strain may help modulate the production of inflammatory markers like IL-8 in intestinal cells.⁶ Another study in PLOS ONE found that supplementation with ATCC PTA 6475 showed a tendency toward reduced IL-6 levels (an inflammatory cytokine) in adults with IBS.⁷

A year-long study published in NPJ Biofilms and Microbiomes demonstrated that supplementation with L. reuteri ATCC PTA 6475 was associated with changes in gut microbiota composition, including decreased E. coli and increased short-chain fatty acid-producing bacteria, which are associated with healthy gut ecosystem function.⁸

How L. reuteri DSM 17938 May Support Immune Function

While ATCC PTA 6475 focuses on supporting healthy inflammatory balance, DSM 17938 has been studied for its potential effects on immune function. Research suggests that DSM 17938 may help support the body's natural immune responses.

A study in Frontiers in Pediatrics found that supplementation with L. reuteri DSM 17938 was associated with increased expression of CCR7 in infants, a receptor involved in immune cell communication.⁹ Another study showed that adults who supplemented with L. reuteri DSM 17938 exhibited higher antibody levels following COVID-19 vaccination compared to placebo, suggesting this strain may help support the body's immune response to vaccination.¹⁰

Research on Combined Strains: Supporting Gut Health and Inflammatory Balance

When these two strains of Limosilactobacillus reuteri are taken together, the science suggests they may work synergistically. A randomized controlled trial published in Frontiers in Gastroenterology examined adults who took both L. reuteri DSM 17938 and ATCC PTA 6475 for 14 weeks. After 14 weeks, people taking both L. reuteri strains were significantly more likely to achieve clinically meaningful improvements in IBS symptoms compared to placebo, along with greater reductions in inflammatory markers.¹¹

Why does gut barrier function matter? A healthy gut barrier helps maintain the integrity of the intestinal lining, which plays an important role in overall immune health. Supporting your gut microbiome with these specific probiotic strains may be one way to help maintain immune health naturally.

Research Evidence: Studies in Children and Adults

Multiple clinical trials have examined the specific L. reuteri strains found in Zoguri in the context of upper respiratory symptoms:

A study published in Beneficial Microbes followed 70 children with pharyngitis and tonsillitis. Those who received L. reuteri ATCC PTA 5289 combined with DSM 17938 as an adjunct to standard care experienced resolution of fever by day two, compared to ongoing fevers in the placebo group. They also showed significant improvements in symptom severity scores for sore throat, runny nose, and nasal congestion, along with reduced TNF-alpha (an inflammation marker).¹²

A review in European Journal of Pediatrics summarized randomized controlled trials in infants and children, including studies conducted in daycare settings, and reported that L. reuteri DSM 17938 was associated with fewer episodes of diarrhea and respiratory symptoms compared to placebo.¹³

In adults, research has shown that L. reuteri supplementation may help support immune responses, as demonstrated in the vaccination study mentioned above.¹⁰

A Personal Experience

Dan, the founder of Zoguri, saw firsthand how supporting gut health made a big difference for his own son. Like many kids, his son experienced frequent illnesses that kept him home from school. After taking Zoguri daily, Dan observed that his son had 79% fewer missed school days over the following 12 months. While this reflects one family's personal experience and individual results will vary, it inspired Dan to make Zoguri available to other families seeking to support their immune wellness.
Click to learn how Zoguri may support your immune health and overall wellness.

Take Action: 5 Steps to Support Immune Health

While we can't control the viruses circulating around us, we can support our gut health and give our immune systems foundational support. Here's what you can do starting today:

REPLENISH BENEFICIAL GUT BACTERIA - Consider adding a probiotic supplement that contains both L. reuteri ATCC PTA 6475 and DSM 17938 to your daily routine. Zoguri is specifically formulated with these two science-backed keystone strains, along with five additional beneficial bacteria species, to help support your gut.

FEED YOUR GOOD BACTERIA - Probiotics need food to thrive. Load up on prebiotic-rich foods like dark leafy greens, berries, legumes, and whole grains. These fiber-packed foods help your beneficial bacteria flourish and support healthy digestion.

PRIORITIZE SLEEP - Your immune system does important work while you sleep. Aim for 7 to 9 hours each night to give your body time to repair and recharge.

MANAGE STRESS - Chronic stress can affect your gut bacteria and overall wellness. Find practices that help you unwind, whether it's meditation, exercise, time in nature, or simply taking a few deep breaths throughout your day.

STAY HYDRATED - Water helps support your body's natural processes and keeps your mucous membranes functioning properly, which is part of your body's natural defense system.

The Bottom Line

This flu season doesn't have to leave you feeling helpless. While vaccines and hand-washing remain important, supporting your gut health may be a powerful complement to these practices. By replenishing beneficial keystone bacteria like L. reuteri ATCC PTA 6475 and DSM 17938, you're giving your gut microbiome and immune system the foundational support they need.

You deserve to spend your energy living your life and supporting your body's natural wellness. Here's to supporting your health from the inside out!

 

¹ Centers for Disease Control and Prevention. "Preliminary Estimated Flu Disease Burden 2025-2026 Flu Season." CDC Flu Burden, November 2025.

² Wiertsema, S. P., et al. "The Interplay between the Gut Microbiome and the Immune System in the Context of Infectious Diseases throughout Life and the Role of Nutrition in Optimizing Treatment Strategies." Nutrients, vol. 13, no. 3, 2021.

³ Sender, R., et al. "The total mass, number, and distribution of immune cells in the human body." Proceedings of the National Academy of Sciences, vol. 120, no. 44, 2023.

⁴ Mu, Qinghui, et al. "Role of Lactobacillus reuteri in Human Health and Diseases." Frontiers in Microbiology, vol. 9, 2018.

⁵ Farhana, A. "Lactobacillus reuteri Paradigm -- How Loss of a Sentinel of Gut-Brain-Metabolic Health Fuels Modern Epidemics and Era of Microbial Restoration." International Journal of Health Sciences (Qassim), 2025, pp. 1--4.

⁶ Jones, Samuel E., et al. "Human-derived probiotic Lactobacillus reuteri strains differentially reduce intestinal inflammation." American Journal of Physiology-Gastrointestinal and Liver Physiology, vol. 299, no. 5, 2010, pp. G1087--G1096.

⁷ Schreiber, Olof, et al. "The effects of a 6-week intervention with Limosilactobacillus reuteri ATCC PTA 6475 alone and in combination with L. reuteri DSM 17938 on gut barrier function, immune markers, and symptoms in patients with IBS-D." PLOS ONE, vol. 19, no. 11, 2024.

⁸ Li, Peishun, et al. "One-year supplementation with Lactobacillus reuteri ATCC PTA 6475 counteracts a degradation of gut microbiota in older women with low bone mineral density." NPJ Biofilms and Microbiomes, vol. 8, no. 1, 2022.

⁹ Savino, F., et al. "Lactobacillus reuteri DSM 17938 Probiotics May Increase CC-Chemokine Receptor 7 Expression in Infants Treated for Colic." Frontiers in Pediatrics, vol. 7, 2019.

¹⁰ Vlasova, Anastasia N., et al. "Limosilactobacillus reuteri DSM 17938 supplementation and SARS-CoV-2 specific antibody response in healthy adults: a randomized, triple-blinded, placebo-controlled trial." Gut Microbes, vol. 15, no. 1, 2023.

¹¹ Cruchet, S., et al. "Limosilactobacillus reuteri DSM 17938 and ATCC PTA 6475 for the treatment of moderate to severe irritable bowel syndrome in adults: a randomized controlled trial." Frontiers in Gastroenterology, 2024.

¹² Maya-Barrios, A., et al. "Limosilactobacillus reuteri ATCC PTA 5289 and DSM 17938 as adjuvants to improve evolution of pharyngitis/tonsillitis in children: randomised controlled trial." Beneficial Microbes, vol. 12, no. 2, 2021, pp. 137--145.

¹³ Gutierrez, Gabriela, et al. "The efficacy of Lactobacillus reuteri DSM 17938 in infants and children: a review of the current evidence." European Journal of Pediatrics, vol. 173, no. 10, 2014, pp. 1247--1261.