The asthma epidemic in recent years has been correlated with increased consumption of a Western-style diet which lacks fibre. In addition, a high fibre intake was shown to prevent allergic responses in experiments using mice. However, it was unclear how long the benefits of such a diet could last and when dietary fibre intake is most beneficial.
Charles Mackay and colleagues fed pregnant mice diets with different levels of fibre, then exposed their adult offspring to asthma-inducing allergens. The mice exposed to a high-fibre diet in the womb were resistant to asthma development as adults. The authors find that this is because the digestion of fibre by certain gut bacteria produces metabolites that are taken up into the bloodstream and that these suppress inflammatory and allergic reactions. These metabolites also have epigenetic effects on the mouse foetus, suppressing certain genes linked to both human asthma and allergic airways disease (a mouse model for human asthma).
The authors also found that a high fibre diet in pregnant women results in the presence of the same metabolites, and that these are associated with a significant decrease in infants requiring more than 2 visits to the doctor for respiratory complaints in their first year of life.