Dietary fibres protect against asthma

The Western diet probably has more to do with the asthma epidemic than has been assumed so far because developing asthma is related to the amount of fruit and vegetables consumed. Gut bacteria ferment the dietary fibres contained in them and fatty acids enter the blood as a result, influencing the immune response in the lungs. This has been shown by a research project funded by the Swiss National Science Foundation (SNSF).

In the West, an increasing number of people have developed allergic asthma in the past fifty years. But dietary habits have also changed during the same period: fruit and vegetables are playing an ever smaller role in people's diets. Now new results suggest that these two developments are not merely simultaneous, they are also causally linked. A team of researchers led by Benjamin Marsland from Lausanne University Hospital (CHUV) has shown in experiments with mice that the lack of fermentable fibres in people's diet paves the way for allergic inflammatory reactions in the lungs.

Influence extends to the lungs

Researchers have already known for some time that the microbial diversity in the gut when digesting and fermenting fibres plays a significant role in preventing intestinal cancer. "We are now showing for the first time that the influence of extends much further, namely up to the lungs," says Marsland. His team either put mice on a with four percent fermentable fibres or gave them low-fibre food with merely 0.3 percent fermentable fibres. This low-fibre food is largely comparable to the Western diet, which contains no more than 0.6 percent fibres on average.

When the researchers exposed the mice to an extract of house dust mites, the mice with the low-fibre food developed a stronger allergic reaction with much more mucus in the lungs than the mice with the standard diet. Conversely, a comparison between mice on a standard diet and mice who received food enriched with fermentable fibres likewise showed that these dietary fibres have a protective influence.

This protection is the result of a multi-level reaction chain, as Marsland's team has now shown. First the fibres reach the intestine, where they are fermented by bacteria and transformed into short-chain . These acids then enter the bloodstream and influence the development of immune cells in the bone marrow. Attracted by the extract of house dust mites, these immune cells wander into the lungs, where they eventually trigger a weaker allergic response.

Another reason why fruit and vegetables are good for you

Marsland thinks that the results obtained by his group are clinically relevant not only because the share of plant fibres in Western diets is comparable to the low-fibre food of the mice, but also because the examined aspects of the immune system are virtually indistinguishable in and humans. Many questions still remain unanswered. "We plan to conduct clinical studies to find out how a diet enriched with fermentable fibres affects allergies and inflammations." It is already sufficiently clear, however, that here is another reason why one should eat more .

More information: Aurélien Trompette, Eva Gollwitzer, Koshika Yadava, Anke K. Sichelstiel, Norbert Sprenger, Catherine Ngom-Bru, Carine G. Blanchard, Tobias M. Junt, Laurent P. Nicod, Nicola L. Harris, Benjamin J. Marsland (2014). "Gut microbiota metabolism of dietary fiber influences allergic airway disease and hematopoiesis through GPR41." Nature Medicine. DOI: 10.1038/nm.3444

Related Stories

A treatment for obesity-associated asthma

Dec 16, 2013

(Medical Xpress)—Research conducted at Boston Children's Hospital indicates that obesity might cause asthma via factors in the immune system and suggests a new way of treating asthma in obese people—who often respond ...

Your gut's what you eat, too

Jan 03, 2014

As the saying goes, you are what you eat. But new evidence suggests that the same may also be true for the microbes in your gut.

Men in Crete live six years longer than men in Zutphen

Dec 18, 2013

Men in the Dutch city of Zutphen in the Netherlands live six years shorter than their peers on the Greek island of Crete. This has been shown by the Seven Countries Study, which involved middle-aged men from ...

Recommended for you

Asthma outcomes worse in older women

Aug 21, 2014

(HealthDay)—Older women face increased challenges in managing their asthma, according to a review published in the August issue of the Annals of Allergy, Asthma & Immunology.

Study reveals nervous system's role in asthma attacks

Jul 22, 2014

(Medical Xpress)—Asthma is a debilitating condition that kills 250,000 people around the world each year. People with asthma have hyperreactive airways and thickened lung walls obstructed with mucus. During ...

User comments