High Fiber Diet May Decrease Severity of Asthma Reaction

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If you have asthma, you have an extra reason to focus on eating more fruits and vegetables. It may help reduce the severity of your symptoms.

Asthma is a chronic (long-term) lung disease that inflames and narrows the airways. The disease causes recurring periods of wheezing (a whistling sound when you breathe), chest tightness, shortness of breath, and coughing. The coughing often occurs at night or early in the morning.

Asthma affects people of all ages, but it most often starts during childhood. In the United States, more than 25 million people are known to have asthma; about 7 million are children.

Over recent decades, the incidence of allergic asthma has increased in developing countries, while the consumption of dietary fiber – especially from fruits and vegetables – has decreased. The finding is more than just coincidental.

Researchers at Lausanne University Hospital studied the effect of diet on mice through an effort funded by the Swiss National Science Foundation. A group of mice fed a low-fiber diet developed worse lung inflammation during an allergen challenge (dust mites). The animals reacted with much more mucus in the lungs than those on the “control” diet.

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Conversely, those animals fed a high fiber diet, particularly one rich in “fermentable fibers” such as pectin showed that the nutrients provided a protective influence.

High fiber diets, says Benjamin Marsland who led the study, do not just protect the gut. The protection extends to other parts of the body, including the lungs. The study found that dietary fiber alters the composition of bacteria in the gut. These then release metabolites which enter the blood stream and influence the development of immune cells. These short-chain fatty acids help reduce levels of inflammation throughout the body, including within the lungs.

The western diet – ie, high fat, high sugar, low fiber – has been much studied recently with regards to its effect on asthma. Recently, researchers from West Virginia University School of Medicine found that poor diet plus a lack of exercise lead to an imbalance in metabolism that may also increase a child’s risk of developing asthma.

Another study, conducted by Dr. Gabriele Nagel of the Insitute of Epidemiology at Ulm University in Germany, found that the diet most protective against asthma symptoms was the Mediterranean Diet. The component with the most protection was fruit, a food typically high in pectin, especially apples, grapefruit, oranges and apricots. Also protective were green vegetables and fish (versus fatty burgers and fries).

Journal Reference:
Aurélien Trompette, Benjamin J Marsland et al. Gut microbiota metabolism of dietary fiber influences allergic airway disease and hematopoiesis. Nature Medicine, 2014; DOI:10.1038/nm.3444

Additional Resources:
National Institutes of Health – What is Asthma?

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