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What Does Gut Bacteria Have to Do with Asthma?

Reading time | 5 mins

I was diagnosed with asthma just before my 17th birthday, after a fair amount of arguing with my doctor that the persistent “bronchitis” I was being treated for wasn’t bronchitis at all. Although I will never know the exact “cause” of my asthma, I have several risk factors for developing the disease. The factors that likely predisposed me to developing asthma include:

  • my family history (although neither of my parents have it)
  • atopy (a genetic tendency toward allergic diseases)
  • being born 10 weeks premature via cesarean delivery, commonly referred to as a C-section
  • my mother had an infection while pregnant that required antibiotics

I’m sure I’m leaving something out, but those are the main offenders when it comes to my asthma. Looking at all these risk factors, I’m surprised I didn’t get asthma earlier than I did.

As a data enthusiast and asthma patient advocate, I’m always hungry for the latest research into what causes and triggers this chronic condition, and how those of us living with asthma can find better ways to cope.

So when I came across research looking into a possible cause of asthma pertaining both to C-section babies and those of us with asthma in general, my interest piqued. This new area of research concerns the role of gut bacteria in asthma development.

I know what you’re thinking: What does a lung condition have to do with your gut?

Unwrapping the science between gut bacteria and asthma is a lot to unpack, so let’s take this theory step-by-step.

We’ll start by looking at the hygiene hypothesis and the role of bacteria exposure in possibly preventing asthma, and move on to what gut bacteria actually is and what it does in the body.

Finally, we’ll consider whether there are any practical implications of this research for people living with asthma.

The hygiene hypothesis

Developing fetuses are protected from bacteria thanks to an incredibly sterile, germ-free environment within the womb. For babies born vaginally, bacterial exposure begins during the exit from the birth canal, and this may have a life-long effect on the immune system. Researchsuggests this process can kick-start the body’s ability to fight off germs.

Those of us born by C-section miss out on this extra burst of bacteria, research has found. As a result, we don’t get that immune system boost as we enter the world.

After birth, we’re exposed to an ever-evolving ecosystem of bacteria. Repeated exposure may help our immune systems develop, enabling us to fight common infections and preventing hyper-response to everyday substances (think allergies).

This is the backbone of the hygiene hypothesis. It’s one possible explanation for what predisposes some of us to asthma and allergies. 

Are we helping or harming children with our societal diligence toward disinfecting and sanitizing every surface, and therefore preventing exposure to certain germs? The hygiene hypothesis makes a good case.

Studies indicate children who are more frequently in contact with other children — such as those in day care or with large families and several siblings — may have lower risk of developing asthma. The same is true for children raised on farms who are exposed to livestock and other animals. These scenarios prompt the immune system to respond to germs, and in turn, to develop resistance to those germs.

However, the hygiene hypothesis remains just that — a hypothesis. It hasn’t been proven. Studies supporting the hygiene hypothesis have been met with research disputing it.

Bring it on: Tying in gut bacteria

While the hygiene hypothesis may be disputed, the role of gut bacteria in immune system development has been well-documented.

Some types of gut bacteria are good for us and help to control our future health. These “healthy” gut bacteria developed in infancy may set the stage for disease development throughout the lifespan. Similarly, the destruction of those healthy gut bacteria by way of antibiotics may impact us for the rest of our lives.

Asthma is a condition characterised by hyper-responsiveness of the airway. Could it be we simply didn’t develop the right bacteria to sensitize our bodies — our lungs — to everyday stimuli, such as allergens? The research in this area is new, but promising, and may help explain why the disease develops in some people but not others.

Infants with low levels of specific gut bacteria at specific age markers have demonstrated increased incidence of allergies and asthma later in life, according to a recent study. Applying these findings to mice, however, brought some hope: It may be possible to manipulate the gut bacteria and mitigate risk of developing asthma.

Dr. Stuart Turvey at University of British Columbia, quoted in TIME Health, stated he hopes this research will lead to the development of approaches to prevent asthma and allergies. It’s possible that someday providing a probiotic supplement in infancy could ultimately prevent asthma from developing.

We’re not there yet, but there is hope in future research developments.

Practical aspects: Could probiotics help me even though I have asthma?

If probiotics could be used to promote good bacterial growth in infants, potentially preventing asthma and allergies, could those probiotic supplements on the market now help with asthma? After all, the theory remains the same — we simply need to rebalance what’s gone awry in the gut to solve this asthma thing, right?

Not so fast.

Multifaceted claims about the wonders of probiotic supplements are rampant online. But when it comes to asthma, they are generally not well-supported by research. Of the limited research available, the results tend to differ from study to study. Probiotic supplements can be expensive, and based on the research that is available, they may not produce any significant benefit for treating asthma or allergies.

People with compromised immune systems may also need to be cautious about taking probiotics due to the bacteria they introduce to the body. If you’re considering a probiotic supplement, speak with your doctor to ensure it’s safe for you, as many asthma treatments can compromise your immune system to some degree. Probiotics may be safe if you’re curious, but only your doctor can provide this advice.

Because research to date focuses on altering the gut bacteria during infancy while the immune system is still developing, more information is needed before we can be certain about the impacts of probiotics on asthma, and which probiotic strains are likely to be beneficial.

Looking ahead in asthma research

As someone living with asthma, I share Dr. Turvey’s hope that the key to preventing the disease may lie in gut bacteria.

Imagine if a simple probiotic supplement could prevent millions of children from developing asthma, whether or not they face extra risk factors (like me). What if we could predict who is going to get asthma more easily and have an isolated marker for it — in gut bacteria?

We aren’t there yet, but hopefully this developing research can provide clues that show us better ways to treat asthma, if not prevent it entirely. Although we might have to wait a while for researchers to make the next big breakthrough, there’s reason to believe that the future for new potential treatments looks bright.