Promoting beneficial gut bacteria through the use of prebiotics could help ease asthma caused by physical activity, shows a new study published in the British Journal of Nutrition.

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Researchers say prebiotics could help reduce the severity of exercise-induced asthma.

Asthma is one of the most common respiratory conditions in the United States, affecting around 17.7 million adults and 6.3 million children.

The condition is characterized by inflammation and narrowing of the airways, which can cause shortness of breath, chest tightness, coughing, and wheezing.

There are two types of asthma: allergic and nonallergic. Allergic asthma can be triggered by allergens, such as pollen, dust and mold, while nonallergic asthma can be triggered by other factors, including stress, exercise, illnesses, and medications.

However, up to 90 percent of patients with asthma - whether allergic or nonallergic - experience symptoms during or after exercise.

There is no cure for asthma; healthcare professionals recommend avoiding asthma triggers in order to prevent flare-ups, and current medications - such as anti-inflammatory drugs - focus on alleviating symptoms of the condition.

Now, research led by scientists from Nottingham Trent University in the United Kingdom suggests a possible new avenue of treatment for individuals with exercise-induced asthma: prebiotics.

Prebiotics and gut bacteria

Prebiotics are nondigestible carbohydrates present in a number of foods, including bananas, oatmeal, and Jerusalem artichokes. They promote the growth of "good" gut bacteria, helping to maintain a healthy digestive system.

Lead study author Dr. Neil Williams - of the Department of Sport Science and the Sport, Health and Performance Enhancement (SHAPE) Research Centre at Nottingham - and colleagues note that a number of studies have suggested a link between gut microbes, immune system activity, and allergies.

"We are only just starting to understand the role the gut microbiome plays in health and disease, and it is becoming increasingly recognized that microbes living in the gut can have a substantial influence on immune function and allergies which is likely to be important in airway disease," says Dr. Williams.

For their double-blind, placebo-controlled trial, Dr. Williams and colleagues set out to investigate how a prebiotic supplement called Bimuno-galactooligosaccharide (B-GOS) might affect asthma severity.

B-GOS reduced markers of airway inflammation, improved lung function

The team enrolled 10 individuals with exercise-induced asthma, alongside eight subjects without a history of asthma, who formed the control group.

Participants were randomized to receive either the B-GOS supplement for 3 weeks, followed by a 2-week "washout" period - during which subjects received no treatment - before taking a placebo supplement for a further 3 weeks.

Each supplement was identical in taste, texture, and color, the authors note.

At study baseline and after each 3-week treatment period, subjects' blood samples were assessed for markers of airway inflammation. Additionally, participants underwent a hyperventilation test - which induces the symptoms of exercise-induced asthma - and their pulmonary function, or lung function, was measured.

While the control group showed no improvement in lung function following B-GOS supplementation, the prebiotic led to significant improvement in this area for subjects with exercise-induced asthma, compared with placebo.

What is more, participants with exercise-induced asthma experienced reductions in blood markers of airway inflammation - including C-reactive protein (CRP) and chemokine CC ligand 17 (CCL17) - after taking B-GOS.

The researchers say their results suggest B-GOS may be an effective treatment for patients with exercise-induced asthma:

"These findings suggest that B-GOS, through its impact on the gut microbiota, has the potential to modulate the underlying immunopathology of asthma, and thereby attenuate the airway hyper-responsiveness associated with HIB/EIB [hyperpnea-induced bronchoconstriction/exercise-induced bronchoconstriction]."

While the exact mechanisms by which B-GOS may ease severity of exercise-induced asthma are unclear, Dr. Williams says it is likely down to its promotion of good gut bacteria.

"This [...] may reduce the inflammatory response of the airways in asthma patients to exercise. Importantly, the level of improvement in lung function that appears after the prebiotic is perceivable by the patient and therefore potentially clinically relevant," he adds.

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