Eat your fruits and veggies, says a new study published in a recent online issue of Nature Medicine. According to a recent study funded by the Swiss National Science Foundation (SNSF), a high fiber diet may reduce the risk of asthma.
Researchers led by Benjamin Marsland, an assistant professor at Lausanne University Hospital (CHUV) in Switzerland, used laboratory mice to investigate a potential link between a high fiber diet and a reduced risk of developing asthma.
Asthma is a chronic lung disease that inflames and narrows the airways. Symptoms include wheezing, coughing, chest tightness, and shortness of breath. Over the past 50 years, rates of allergic asthma have increased in the United States.
At the same time, the amount of high-fiber fruits and vegetables featured in the typical Western diet has decreased.
To determine a link, if any, between a high fiber diet and a reduced risk of asthma, the researchers compared three groups of lab mice. One group ate a low-fiber diet comparable to a Western diet, averaging no more than 0.6 percent fiber. The second group ate a standard diet consisting of four percent fermentable fiber. The third group ate a standard diet enriched with fermentable fibers.
The researchers also exposed the mice to an extract of house dust mites in order to provoke an allergic reaction.
The mice on the low-fiber diets experienced the strongest allergic reactions, developing more mucus in the lungs, than the mice on the standard diets. Furthermore, the mice who consumed the enriched fiber diet exhibited an even stronger protective effect than the mice on the standard diet.
In other words, eating a diet full of high-fiber fruits and vegetables provides protection against allergic asthma reactions.
The researchers believe that the protection against asthma offered by a high fiber diet is the result of gut bacteria. Previous studies have confirmed that having a rich and diverse mix of microbes in the gut that digests and ferments fiber helps prevent cancer of the intestines. A more recent study also discovered a link between gut microbes and a reduced risk of asthma: Children who grow up with dogs in the house have a decreased risk of allergies and asthma due to changes in gut microbes.
Prof. Marsland explains, “We are now showing for the first time that the influence of gut bacteria extends much further, namely up to the lungs.”
Upon further examination, the researchers discovered that the protective effect of a high fiber diet rich in fruits and vegetables is the result of a series of reactions that occur when the fiber reaches the intestines, is fermented by gut bacteria, and is transformed into short-chain fatty acids. After entering the bloodstream, these short-chain fatty acids affect the development of immune cells in the bone marrow. When an allergen enters the body, immune cells trigger an allergic response. The strength of the allergic response depends on the effect of the short-chain fatty acids.
Prof. Marsland believes that the findings of this study are significant for two reasons. First, the results indicate that a low fiber diet increase the risk of allergic asthma. Second, the results are applicable to humans because the parts of the immune system involved in mice is almost indistinguishable from that of humans.
Although more research is necessary, this study indicates that diets rich in high-fiber fruits and vegetables provide more protection against disease than previously thought.
References
Gut microbiota metabolism of dietary fiber influences allergic airway disease and hematopoiesis: http://www.nature.com/nm/journal/v20/n2/full/nm.3444.html
High fiber diet may protect against asthma: http://www.medicalnewstoday.com/articles/270827.php
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