Around 20% of children population in Western countries have asthma, the most prevalent child chronic health condition. Worldwide, there are 235 million asthmatic people, according to World Health Organisation. Until now, the disease was associated to a combination of genetic and environmental factors, such as air pollution. Some recent studies had also demonstrated in animal models that an altered gut microbiota early in life could also have an influence in the developing of asthma later on. Unfortunately, scientists did not know whether that link could also be applied in humans.
As we have already explained in this blog, in a 2015 study published in Science Translational Medicine, a team of researchers and paediatricians from University of British Columbia, in Canada, demonstrated for the very first time in humans the key role gut microbiota play during the first three months of life in training the immune system. And how, also, alterations during that specific window of time could lead to asthma.
The paediatrician Stuart Turvey is one of the co-author of that revealing research and he was one of the experts attending to a Barcelona Bdebate conference held at the Cosmocaixa Science Museum dedicated to the human gut microbiome on June 30 and July 1. There we could interview him and talked about the link of immune system diseases, like asthma, and alterations in gut microbiota.
What is the link between asthma and gut microbiota?
It is complicated and interesting, because asthma is a disease in the lungs and the microbiota is in the gut. The link is seems to be from the metabolites that the bacteria make. The bacteria are digesting food but they also are releasing chemicals, which go to the blood stream. And we know those chemicals are very important to train the immune system. In fact, without that bacterial training, our defence system gets confused and causes lung inflammation or other immune problems.
So the bacteria make metabolites and they train the immune system. When anything happens in this chain of tasks, problems arise.
We should be cautious. The mechanisms that we have seen and that we have evidence to support are through the metabolite. But the bacteria that live inside us are complicated machines as well. So apart from making metabolites they also likely train the immune system in other ways that we don’t exactly understand. The importance of our research is that we have seen that if you don’t have the right bacteria very early in life, that’s when you run into problems like asthma.
Can we be more specific about early life? Is it about the first months or years?
We think that there is a window of time, which contains the first 100 days, the first three months of life. That is when you may need the right bacteria to train your immune system. We have observed that if those bacteria are not there, in the training, that seems to be the linked to asthma.
How did you find out the link between asthma and gut bacteria?
We recruited pregnant mothers for our study. Then, after the babies were born, we collected different samples and we found that in the stool samples of three months of age, when there were low levels of four specific bacteria, later on the children went to have asthma by age 3 years (the study is ongoing so we are following up the children to see if the gut microbiome is also related to asthma beyond age 3 years). Then we did some mice experiments and we showed that if we gave those four bacteria deliberately back to the animals, that protected them from developing asthma.
Which were those bacteria?
We nicknamed then FLVR, because they have long Latin names: Faecalibacterium, Lachnospira, Veillonella and Rothia. These were the four we found to be in low levels in the babies who went to have asthma.
Can we use probiotics to restore those FLVR bacteria in babies and prevent asthma, as in your study with mice?
I am a paediatrician and my goal is certainly to prevent asthma before it starts. And a long-term goal is to see whether we could give safe versions of the FLVR bacteria to babies, a little bit like probiotics. Today the probiotics available in the supermarket have different bacteria, but not FLVR in them. Our goal is to design and develop a specific cocktail of bacteria for those babies, but before we need to make sure it is safe before, obviously.
Why do some babies lack those FLVR gut microbiota during those first 100 days?
We don’t know the answer yet. Our study wasn’t set up to look at why some children were low or some children were high. We only looked at the differences and saw what happened to their health. Now we are doing studies with more children to see whether the differences in the mother’s diet or the way the baby was delivered, caesarean or vaginally, may shed some light on that question.
Do you think that the lack of the FLVR bacteria can be linked also to other immune health problems?
Potentially, they might be. In our study we only looked at this one health outcome, asthma. But in the Canadian Child Study we were also very interested in other things related to children’s health, such as obesity; we are looking to see if the gut microbiota would predict which children would become obese or have other health problems. Maybe there are different diseases for which different bacteria are important. Or maybe there is a small set of bacteria that if missing you get a variety of immune system problems, such as celiac disease.
Different factors have been linked to the increase of cases of asthma in western societies, such as pollution or the hygiene hypothesis.
Air pollution and smoking in the home are certainly risk factors for asthma. But the gut microbiota is also one of those likely environmental risk factors also related to the disease. Would having a healthy gut microbiome protect against pollution or against smoking? That is an important question. If we could get the answer, maybe one effective intervention in the gut microbiota of the children could minimize the impact of other things.
Is there anything families can do to keep their babies’ gut microbiota as healthy as possible?
Breast-feeding is protective and helps mitigate other health problems. So, if possible, breast-feeding is to be encouraged. Also, we should minimise the use of antibiotics, just make a proper and thoughtful use of antibiotics. And, of course, another things families can do is simply let the children be out in the world. It is not helpful to lock them up to not expose them to anything. We should be comfortable to let them go and live and explore in the environment.