Do Probiotics Help the Immune System? Probiotics and Upper Respiratory Infections

Being sick is not fun. For years, the scientific communities have looked into ways to bolster our body’s defense army, the immune system. Probiotics have become one of the candidates for this. But do probiotics really help the immune system? This article aims to answer that question hopefully. We will be looking at how probiotics can help us thwart one of the most common types of infection: upper respiratory infection. If you want to refresh yourself on what probiotics are, head to this article for a quick refresher.

Why focus on the upper respiratory infection (URI)?

Upper respiratory infections (URI) are very common. More patients visit doctors’ offices and the emergency departments because of URIs than any infections. Most people, even healthy individuals, probably have experienced at least one URI before. How do these infections happen? It usually starts with bacteria, viruses, or both getting inside our body when we breathe in. Our body’s immune system recognizes foreign invaders and attempts to eliminate them. If they are successful, you either have mild symptoms or none at all. If they are not, the symptoms can worsen and potentially lead to respiratory failure. Have you experienced a URI before? Feel free to share your experience in the comment box below! Let’s talk more about URI.

URI is a term that is used to describe a collection of infections that happen within the upper respiratory system. That includes infections in the throat, the nose, and the ears. So while you may not have heard of URI, chances are that you know about an ear infection, sinus infection, strep throat, a cold, and the flu. Because they are so common, any chance we have of reducing the number of people getting URI can be impactful. Probiotics were raised as one of the prime candidates for boosting our immune system to prevent URI.

How do probiotics improve our chances against URI?

The immune system can be very complicated. Here, we will talk about how probiotics boost our immune system. Because of this, this section will contain several scientific terminologies and concepts. If you don’t want to get into that, the quick summary is that probiotics trigger an increase in several immune agents in our body, which leads to our body having more agents to fight off foreign invaders (bacteria and viruses). Because we have more agents to fight, theoretically, our body should have an easier time eliminating them and preventing infections. Continue to read below if you want more details on the process, or skip to the section. “Do they actually work?”

Probiotics have been reported to enhance the functions of the immune system both in innate and adaptive immunities. In innate immunities, the focus is on the interaction between probiotics, intestinal epithelial cells, and intestinal immune cells. The interaction increases the activities of phagocytosing immune agents called macrophages, which can go around the body and phagocytize or “eat” foreign bacteria. Another innate immune system effect that probiotics have is increasing the effectiveness of natural killer cells, whose duty is to consume foreign bacteria and viruses.

As mentioned, probiotics also have impacts on the adaptive immune system. Where the innate immune system works with non-specialized agents that can fight against multiple types of invaders, the adaptive immune system work with specialized agents that are very effective against a single kind of invader. These specialized agents are known as immunoglobulins. Probiotics have been reported to induce an increase in immunoglobulin A (IgA), which work in tandem with macrophages to eliminate foreign invaders that macrophages cannot deal with.

So we know how probiotics work with our body to boost our immune system, but does the boost actually translate to a reduction in upper respiratory infections?

Do they actually work?

Quick answer: There is no clear-cut answer to this just yet.

Most of the studies that have been published thus far demonstrated that the amount of relevant immune agents, as well as their activities, are increased in participants who took probiotics compared to participants who did not. Some of these differences were considered “non-significant,” which means that the differences that they saw during the studies may be due to random chances and that there may not be any difference. The studies’ result implies that this boost in relevant immune agents should enhance the immune system and provide some health benefits that lead to a lower incidence of URI.

A study conducted in Japan in 2013 demonstrated a reduction in the amount of URIs in healthy, aged 30-49 adults. The study participants were given a probiotic once daily for 12 weeks. The probiotics were provided to the participants in the form of fermented milk containing the Lactobacillus casei strain made by Yakult Honsha. The authors reported a significant difference in the number of URIs between participants who received the probiotics and those who did not where 53.2% of the no-probiotics group and 22.4% of the probiotic group had URIs). The same trend was observed with the number of common colds (18.4% vs. 44.7%). The result of this study looks very promising. Still, I want to caution that all of the authors responsible for this study were employed under Yakult Honsha, the company that supplied the probiotics. As such, more studies need to be done to see if the results can be replicated before we can say for certain that probiotics containing Lactobacillus casei help reduce the incidence of URIs.

Specific Strain of Probiotics for URIs?

Because there is no clear-cut answer to whether probiotics help prevent URIs or not, I cannot recommend one strain of probiotics over the other just yet. But, I can say that many studies on this topic have been done with the Lactobacillus family. From the studies that were looked at for this article, there were Lactobacillus fermentum, L. plantarum, L. casei, and L. paracasei.

Conclusion

In conclusion, there is no clear-cut study that comes out to say that probiotics help prevent upper respiratory infections, but there are a lot of data that implies that they should. I hope that this content helps provide clarification for some of you. As usual, if you have any questions or want an article on a specific health topic, please feel free to comment below or reach out to me via email.

Reference

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