Dietary fibres protect the lungs from asthma
10 January 2014
Researchers at Lausanne University Hospital (CHUV) have shown
that fermentable fibres present in fruit and vegetables start a
chain reaction that enables the body to protect the lungs from the
inflammatory response in asthma.
The fermentable fibres are transformed in the gut into
short-chain fatty acids which enter the bloodstream and affect
production of immune cells in the bone marrow. These immune cells in
turn protect the lungs from asthma.
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. It has already been
known for some time that the microbial diversity in the gut when
digesting and fermenting fibres plays a significant role in
preventing intestinal cancer. Now these new results suggest that
asthma and lack of fruit and vegetables in the diet are also
causally linked. So the western diet probably has more to do with
the asthma epidemic than has been assumed so far.
In the study, the researchers either put mice on a standard diet
with 4% fermentable fibres or gave them low-fibre food with merely
0.3% fermentable fibres. This low-fibre food is largely comparable
to the Western diet, which contains no more than 0.6% fibres on
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 showed that these dietary fibres have a protective influence.
This protection is the result of a multi-level reaction chain.
First the fibres reach the intestine, where they are fermented by
bacteria and transformed into short-chain fatty acids. 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.
Lead researcher Benjamin 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 mice and
Many questions still remain unanswered so the team plans 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 to
eat more fruit and vegetables.
Trompette A, et al. Gut microbiota metabolism of dietary
fiber influences allergic airway disease and hematopoiesis through
GPR41. Nature Medicine. 2014. doi: 10.1038/nm.3444