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Published on : Jan 08, 2014

Asthma - the common inflammatory condition that contracts the fluent airways of the lung has drastically increased in several westernized countries since the 1960s; however, it is still not common in the less well-developed countries such as Africa, where an abundant supply of vegetables and fruits forms the bigger chunk of the regular diet. 

According to the latest studies, asthma may ward off from the body system because of a rich fiber diet meal. This simply means that a dietary fiber meal definitely influences various other inflammatory diseases in the system including asthma. 

The fiber that is consumed in vegetables and fruits settles the overzealous activities taking place in the immune system which ultimately leads to irritable bowel syndrome conditions, colon cancer, and Crohn’s disease. When we consume abundant vegetables and fruits, the bacteria that grow inside our body, or perhaps the ones that occur naturally in our intestines, help us stomach the fiber soon. 

In addition, the microbes in the body take soluble fiber such as pectin obtained in citrus fruits, pears, apples, berries, and onions and ferment it into special types of fatty acids that act together with different immune cells. The fatty acids circulate through the bloodstream interacting with immune cells throughout the body. All these aspects help in keeping inflammation in a proper check. However, studies have not clearly explained about the anti-inflammatory going beyond the digestive tract.

Certain tests were run to examine the possible link of this case study, whereby, immunologist Benjamin Marsland of the University of Lausanne in Switzerland and a team of colleagues put a group of mice on a low-fiber diet. After two weeks of constant study of them, the researchers had the mice sniff an allergen compound - which was ideally derived from dust mites. The allergen is originally a key trigger of asthma and human allergy. 

Nevertheless, these mice exhibited inflated asthmatic responses such as inflammatory compounds in the lungs, wheezing, shortness of breath, and constricted airways as familiar to asthmatic patients. 

On the other hand, mice that consumed a diet rich in pectin meal for two weeks before being injected with the allergen exhibited a reduced inflammatory response during the tests. Even the levels of the antibody immunoglobulin E and the immune cells known as eosinophils were increased in allergies, whereas, asthma were nearly halved in condition. The mice even showed less constriction of their airways.

After the scientists analyzed the feces of the mice on the regular low, normal, and high-fiber diets, they realized that the gut bacteria were actually responsible for the fiber-mediated benefits. When the animals were given the pectin, the bacteria were able to generate the anti-inflammatory fatty acids which were twice as prevalent as the former. The researchers examined these animals closely and discovered higher amounts of fatty acids in the stool as well as in their blood. 

However, the message was not clear if the fatty acids in the bloodstream were controlling the immune system in certain ways. And thus, the researchers then injected the mice with propionate. It was after then, and two weeks later, the mice exhibited less constriction of the airways in response and reduced inflammatory markers to the allergen treatment. This was reported online in the Nature Medicine. 

In addition, to the research, the immune cells known as dendritic cells also behaved haphazardly. Depending on the types of immune cells, the dendritic cells can either ramp up the responses of the mice or scale down the immune system. Nonetheless, in this process, the mice on the high-fiber diet could turn on the effector cells, which are one of the key players in the causing allergic asthma in humans as well as mice. 

The final phase of the researchers’ tests however determined that mice that were injected with propionate were basically producing precursor cells that formulate into the dendritic cells protecting against asthma. 

According to Marsland, this was their first study to demonstrate that diet can control the development of immune cells in the bone marrow that could lead to major implications throughout the body, including lungs. 

Gary Huffnagle, an immunologist at the University of Michigan, Ann Arbor, said if researchers had expected that if certain compounds that were developed by the bacteria influenced asthma, the same compounds would influence the lung tissues as well. 

He added that the series of events linking dietary changes, a shift in immune cell production in the bone marrow, altered metabolism of gut bacteria, and relief of asthmatic inflammation is a progressive development. The overall study is a convergence of observations.

Nevertheless, Marsland believes that rigorous scientific work still needs to be done in this sector. Tests need to be conducted on dietary supplements including purified propionate, which may be similar to fatty acids. These compounds might be beneficial for those people who face asthma problems or for those who do not have the fortune to fruits and vegetables. A balanced diet rich in fiber is however the best way out to avail the anti-inflammatory benefits, he adds.