Fruit, Vegetable Fiber Protects Against Asthma

LAUSANNE, SwitzerlandConsuming a diet high in dietary fiber from fruits and vegetables may support the immune response in the lungs, thus protecting against asthma, according to a new study published in the journal Nature Medicine.

Lausanne University Hospital (CHUV) researchers put mice on a standard diet with 4% fermentable fibers or gave them low-fiber food with merely 0.3% fermentable fibers. This low-fiber food is largely comparable to the Western diet, which contains no more than 0.6% fibers on average.

When the researchers exposed the mice to an extract of house dust mites, the mice with the low-fiber 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 fibers likewise showed that these dietary fibers have a protective influence.

This protection is the result of a multi-level reaction chain. The fibers are fermented by bacteria in the intestine and transformed into short-chain fatty acids. These acids 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.

"We are now showing for the first time that the influence of gut bacteria extends much further, namely up to the lungs," said lead researcher Benjamin Marsland.

In a prior study, fruit and vegetable fiber was shown to decrease risk of stroke in persons with type 2 diabetes.