Doctors have been trying to get us all to eat more fibre in our diets for some time now and more recent attempts have focussed around the potential for increased dietary fibre to promote beneficial gut microbe populations (microbiome) that are responsible for many things that affect our health. There are now many articles contains lots of good advice on improving our gut microbiome but the main principles are the same and are supported by the UK NHS - eat a balanced diet.
The typical diet of someone in the UK or US tends to contain a lot of purified simple sugars (white sugar, sugared drinks, confections etc) and processed starches (white bread, white rice, potatoe's, white pasta) which are all OK to eat BUT we should eat them in much lower amounts as they contain very little fibre. Fibre is also a type of highly complex sugar (a carbohydrate) that is resistant to digestion. If we replace as much of this food as we can with foods containing fibre we dramatically slow down sugar intake and thus calories, helping us keep slim, helping us avoid diabetes.
That is not all! Studies are showing us that fibre helps people who have a chronic inflammatory disorder eg people with asthma, by directly calming an overactive immune system. This paper reviews evidence that fibre can directly interact with the mast cells in our gut. Those cells are highly important for triggering our response to microbes and injury ie our inflammatory response and when they come into contact with fibre they are partially deactivated, or at least stopped from over-reacting. Those cells can stop our entire bodies from over-reacting to stimuli such as those that cause asthma attacks.
Foods containing fibre are easy to find - any unprocessed food that comes from plants will be rich in fibre so fruit, vegetables, nuts, seeds are all great sources. Replace white bread with wholemeal, wholegrain breads. Replace processed carbs (sweetened drinks, biscuits, confectionary) with whole fruit drinks (with the bits left in!), nuts & seeds. Replace white rice with brown, replace white pasta with brown. Replace potatoes with sweet potatoes. NB The BBC has been covering this issue for some time now so see their links for help & other suggestions - for example the simple starches in white bread become much more resistant if you freeze it and then toast it! Potatoes & pasta are much better if you chill them overnight after cooking and then reheat.
It has never been more important to eat a balanced diet every day, especially if you have asthma.