Does your diet affect your risk of developing asthma, or how severely it affects you? New research in Switzerland suggests that the consumption of dietary fiber may well influence the course of this common condition.

The Experts Explore

In a recent study underwritten by the Swiss National Science Foundation, some mice were fed a diet containing a hefty amount of fiber, while others ate a very low-fiber diet. All the mice were then given an extract containing house dust mites, a common allergen and asthma trigger. The mice who had eaten the low-fiber diet, similar to a typical Western diet, reacted much more strongly to the dust mites, and developed significantly more lung mucus (a common asthma symptom) than the mice who had eaten greater quantities of dietary fiber.

What’s Fiber Got to Do With it?

Why did the fiber seem to have such an effect on the mice’s asthma symptoms? The answer lies in the immune system, which is how the body defends itself. Inflammation is an immune system response, and while it helps us fight injury and infection, long-term, chronic inflammation is linked with various health issues. Dietary fiber acts as an anti-inflammatory; and the Swiss team showed that in the digestive system, fiber turns into short-chain fatty acids that trigger the production of immune cells. These immune cells then migrate to the lungs, where they effectively blunt the allergic/asthmatic response.

Dietary fiber has a positive effect on the human gastrointestinal system; other studies have shown a link between a higher intake of dietary fiber and lower rates of intestinal cancer. But the Swiss study suggests that dietary fiber’s effects on the inflammatory process can benefit not just the digestive system but the lungs, and possibly other vital organs as well.

Future Research

Mice, of course, are not people and do not develop asthma the way people do. The next step, ideally, would be a similar study using human subjects. "We are planning now to do our first test in humans, for which we are currently trying to raise the funds," says Marsland. In the meantime, given all that we know about the benefits of a high-fiber diet, go ahead and bulk up your diet with fruits and vegetables. While the impact fiber has on asthma is not yet clear, a diet rich in high-fiber fruits and vegetables offers plenty of health benefits.

Benjamin Marsland, associate professor, Lausanne University Hospital reviewed this article.


  1. Benjamin Marsland, associate professor, Lausanne University Hospital. "Dietary Fibres Protect Against Asthma." Swiss National Science Foundation. Accessed 25 February 2014.
  2. Benjamin Marsland, associate professor, Lausanne University Hospital. Email interview. 26 February 2014.  
  3. Kuo, Shiu-Ming. "The Interplay Between Fiber and the Intestinal Microbiome in the Inflammatory Response." Advances in Nutrition 4 (2013): 16-28.
  4. "Asthma Triggers: Gain Control. Dust Mites". Environmental Protection Agency. Last updated April 16, 2014. 
  5. "The Digestive System and How It Works". National Digestive Diseases Information Clearinghouse (NDDIC). Page last updated September 18, 2013.