You’ve probably heard about the gut microbiota (also commonly called “microbiome”). This collection of bacteria, viruses, and fungi is found in nearly every part of the body—our mouths and intestines, for example—and helps maintain good health.
Not long ago, experts believed that our lungs, on the other hand, did not have a microbiota—that they were a sterile environment unless they became infected. But there is growing evidence that the airways have a microbiota of their own. In fact, healthy lungs commonly house many bacteria.
Why does that matter? Knowing that there is an assortment of organisms in our lungs means that researchers can try to manipulate them. That may lead to better treatments for serious lung diseases such as chronic obstructive pulmonary disease (COPD) and asthma.
Early exposure can affect disease
It may seem counterintuitive that when particular bacteria take up residence in our bodies, they can make us healthier. But that’s what researchers have found. For example, children who were exposed to certain bugs as infants—kids who lived on a farm with livestock or had two or more dogs in their home—had lower rates of asthma than those who were not.
Without some of these early influences, the immune system may not get the jump-start that it needs in order to fend off disease later. But it’s complicated. Different studies on children and asthma have found that exposure to other types of bacteria increases a child’s susceptibility to the disease.
Scientists have also looked at the relationship between illness in adults and the microbiota of the lungs. Adults with advanced COPD have a lower diversity of lung bacteria than those with less severe disease. But adults with asthma have higher levels of bacteria in their lungs than healthy people. That seeming contradiction may be because of how the diseases are treated. For example, people with COPD are often given antibiotics or steroids, which can change the bacterial landscape.
A pattern similar to COPD has been found in people with cystic fibrosis. Researchers learned in one study that as the disease got worse, the patients’ lungs had fewer and fewer different kinds of bacteria. They concluded that the antibiotics used to treat infections, which are common in cystic fibrosis, changed the bacteria population.
The role of antibiotics
Beginning largely with the discovery of penicillin, which became widely available in 1944, antibiotics have saved millions of lives. But their role is more complicated today. Overuse of antibiotics has led to resistance to the drugs and the breeding of more powerful bacteria in our bodies. That means that the antibiotics we do have are less effective, and fewer new varieties are being developed.
In addition, we know now that antibiotics can change the microbiota of the gut—which “talk” to other parts of the body, including the lungs, according to a review of recent evidence published in March 2017 in Clinical and Translational Immunology. When the careful balance of the microbiota is altered, our immune defenses can be weakened, as a number of studies have demonstrated.
One study published in 2014 showed that infants who were given antibiotics had a greater chance of developing asthma in childhood. Babies who received five or more courses of antibiotics in the first year of life were twice as likely to develop “persistent” asthma, defined as beginning before age 3 and continuing through ages 4 to 7.
That doesn’t mean that antibiotics are bad. Doctors still depend on them for treating asthma, flare-ups of COPD, and infections in cystic fibrosis. As we learn more about the microbiota of the lungs, more research is being focused on the role antibiotics play in lung disease.
A study published in 2015 in Seminars in Respiratory and Critical Care Medicine looked at patients with non-cystic-fibrosis bronchiectasis, a disease in which the airways are damaged. Scientists found that the type of inhaled antibiotics that patients typically use may not always be ideal for them. The researchers suggested that identifying the specific bacteria in a patient’s lungs could point doctors to a more tailored strategy of treatment and different choice of antibiotics.
When you think about your own health, keep in mind that antibiotics will not work on viruses like the common cold and the flu. Taking them when you don’t need them contributes to the increase of antibiotic-resistant strains of bacteria.
Probiotics and prebiotics
Scientists are excited about exploring new treatments for chronic lung diseases using what they are finding out about the lung microbiota. They also are drawing on research on the gut microbiota, which has a much longer history. As mentioned previously, the two systems affect each other in what experts call “cross-talk.”
That’s why researchers believe that what we eat or ingest may influence our lungs. Many hope probiotics and prebiotics could be important elements in treating lung disease.
Probiotics—the word means “for life”—are defined by the World Health Organization (WHO) as “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host.” Most common among those microorganisms are bacteria in the Lactobacillus and Bifidobacterium families. Certain yeasts may also be present. Evidence has shown that they may work by competing with “bad” bacteria.
Most of us think of probiotics simply as food or supplements that help keep us healthy. Probiotics are found in fermented foods such as yogurt. Prebiotics, on the other hand, don’t contain microorganisms themselves but favor the growth of bacteria that normally live in us. They are non-digestible food ingredients. A commonly cited example of a prebiotic is dietary fiber.
Some very preliminary research shows promise for the use of probiotics for lung diseases and infections. For example, an Italian study, published in the Journal of Pediatric Gastroenterology and Nutrition in 2014, of children and adults with mild to moderate cystic fibrosis found that those who were given drops of a Lactobacillus probiotic for six months had fewer disease flare-ups and upper respiratory tract infections than those who were not.
The bottom line
Probiotics and prebiotics may someday be used to benefit the lung microbiota directly. There may be a way, for example, to remove a microbiota from diseased lungs and install a new one. But research in the area of probiotics and prebiotics and the lungs is in its infancy. Much more study is needed, including high-quality clinical trials in people that focus on asthma, COPD, and pulmonary fibrosis. Before you take any supplement to treat lung disease, talk to your doctor, and keep in mind that supplements are not reviewed for safety and effectiveness by the Food and Drug Administration.
Also see Probiotics Pros and Cons.