It seems like an odd link, diet and breathing, but actually it makes enormous amounts of sense.  Our bodies need nutrients to function effectively.  Nutrition affects every cell from those that make up our bones to those of the skin.  The lungs and the cells of the immune system, both of which are involved in asthma, are no exception.  During an asthma attack the immune system produces certain antibodies (immunoglobulin E) and these stimulate the release of a chemical called histamine in the lining of the airways in the lungs.  The airways consequently become inflamed and swollen, excess mucous is also released and this can block the smaller airways and affect breathing.

The asthma statistics(1) for the UK are shocking.  5.2 million of us are currently receiving treatment for the condition.  1.1 million sufferers are children, that represents 1 in 10 kids, and 4.1 million are adults, that is 1 in 12.  On average there will be 3 children in every classroom who have asthma in the UK.  We also have the highest prevalence of severe wheeze in children aged 13-14 years WORLDWIDE!  Not a position to be proud of.  Every 19minutes a child is admitted to hospital due to their asthma and asthma costs the NHS over £996million per year.  Employers ought to care too as over 12.7million working days are lost to asthma each year.

I am an optimist, so this post is not all doom and gloom!  Dietary change can make a terrific difference!

The decision to write about asthma was prompted by two reasons.  The first was watching a child come out of a fast-food outlet and immediately using his “puffer” medication and the second was that two very interesting studies(2,3) have been published this month which link the adherence to a Mediterranean diet to a reduction in asthma symptoms.

In the first study(2) the scientists looked at the diet of 1784 children who were aged around 4 years, they found that adhering to a traditional Mediterranean diet was a protective factor for wheezing.  The second study(3) looked at diet during pregnancy and what affect that had on children when they were 6 years old.  The results indicate a protective effect of adherence to a Mediterranean diet during pregnancy against asthma-like symptoms (including wheezing and allergy) in childhood.  The lead scientist of the second study, Dr Chatzi, has previously published studies which indicate the protective effects of a Mediterranean diet against asthma symptoms.

So what constitutes a traditional Mediterranean diet?  Basically, this is healthy diet rich in a variety of different fruits and vegetables, legumes (peas and beans), oily fish, nuts and seeds, olive oil and unrefined wholegrains.  The diet is also high in fibre and relatively low in red meat, saturated fats and trans fatty acids (which are abundant in some processed foods).  The total fat content in general is relatively high but the type of fat is monounsaturated and also high in omega 3 fatty acids.  There are many reasons why this kind of healthy balanced diet could reduce the prevalence of asthma symptoms:

Fruits and vegetables are abundantly rich in all sorts of vitamins and flavonoids (a group of over 4000 plant compounds).  Studies (7,8) have shown that the flavonoid quercetin (found abundantly in onions and apples) appears to reduce the risk and severity of asthma symptoms.  This is probably due to the anti-inflammatory properties that quercetin exhibits in the body.  Vitamin C may be particularly important to asthmatics (9) as it seems to reduce the degree of constriction in the airways.  Studies (10) have found that asthma sufferers tend to have lower plasma vitamin C levels than non-asthmatics and supplementation of 1000mg Vitamin C a day may help improve lung function and reduce the frequency and severity of asthma attacks.  As mentioned in the post on hayfever, Vitamin C and Quercetin both act as natural anti-histamines in the body.  Asthmatics tend to have high histamine levels.  Histamine is produced by cells of the immune system and stimulates an inflammatory reaction in the body which may be responsible for the wheezing and shortness of breath in asthma sufferers.

Other vitamins and nutrients found in fruits and vegetables, such as carotenes, have also been implicated as important for prevention of symptoms in asthma sufferers.

Nuts, Seeds and Wholegrains are rich in the mineral magnesium.  A diet high in magnesium may well be useful for asthmatics since this important mineral appears to alleviate the bronchoconstriction (tightening of the airways in the lungs) associated with asthma.  There are many studies (far too many for me to list) which indicate the importance of magnesium in those suffering with asthma.  A study in children showed that low magnesium intakes are associated with poorer lung function(4) another found that asthma patients supplemented with 400 mg magnesium a day showed an improvement in asthma symptom scores(5).  Many studies have also found that asthmatics commonly have lower levels of magnesium in their blood(e.g. 6).  The National Diet and Nutrition Surveys (NDNS) for the UK have found that dietary intakes of magnesium are generally low in most children and women in the UK.  We would all do well to try and include more nuts, seeds and wholegrains into our daily diets. 

Fat:  There is some evidence that asthma may be related to an imbalance in fatty acids in the diet.  An Australian study(11) found that a diet high in omega 6 fatty acids and low in omega 3 fatty acids increased the risk of asthma symptoms in a large group of children.  Excessive amounts of omega-6 fatty acids, found in vegetable oils, and a relative lack of omega-3 fats, found in oily fish such as salmon and mackerel and some nuts and seeds, seems to promote inflammation and aggravate asthma. Inflammatory chemicals produced from omega 6 fats by the immune system can trigger constriction of the airways and mucous production.  Omega 3 fatty acids are involved in the production of anti-inflammatory chemicals by the cells of the immune system. 

One study(12) in asthmatic patients found that supplementation with corn oil (rich in omega-6 fats) tended to increase the production of inflammatory white blood cells, whereas supplementation with perilla seed oil (rich in omega-3 fats) had the opposite effect.  Patients treated with perilla seed oil also had significant increases in their lung function.  In another study(13), supplementation with fish oil (rich in the omega 3-fats) for 10 months reduced asthma symptom scores in a group of children.  Avoidance of excessive amounts of margarine and vegetable oils, and the inclusion of oily fish such as salmon, trout, mackerel and herring (or flaxseed oil for vegetarians) in the diet may, therefore, possibly help to control asthma symptoms.  Using olive oil in place of vegetable oils will probably prove useful as it is a monounsaturated fat and does not contribute to inflammation in the body, indeed it may even play a role in reducing inflammation(14).

In part II I will be covering other important dietary measures that affect asthmatics

(1) Asthma UK www.asthma.org.uk
(2) Castro-Rodriguez JA et al.  2008.  Mediterranean diet as a protective factor for wheezing in preschool children.  J Pediatr.  152(6):823-8, 828
(3) Chatzi L et al.  2008Mediterranean diet in pregnancy is protective for wheeze and atopy in childhood. Thorax.  63(6):507-13
(4) Gilliland FD et al.  2002.  Dietary magnesium, potassium, sodium and children’s lung function.  Am J Epidemiol.  155(2):125-131
(5) Hill J et al.  1997.  Investigation of the effect of short-term change in dietary magnesium intake in asthma.  Eur Respir J.  Oct;10(10):2225-9.
(6) Alamoudi OS.  2000.  Hypomagnesemia in chronic, stable asthmatics: prevalence, correlation with severity and hospitalization.  Eur Resoir J.  16:427-431
(7) Knekt P et al.  2002.  Flavonoid intake and risk of chronic diseases.  Am J Clin Nutr.  76:560-568.
(8) Saheen SO et al.  2001.  Dietary antioxidants and asthma in adults: population-based case-control study.  Am J Respir Crit Care Med.  164:1823-1828
(9) Bielory L et al.  1994.  Asthma and Vitamin C.  Annals Allergy.  73(2):89-96.
(10) Harik-Khan RI et al.  2004.  Serum vitamin levels and the risk of asthma in children.  Am J Epidemiol.  159:351-357.
(11) Oddy WH et al. 2004. Ratio of omega-6 to omega-3 fatty acids and childhood asthma.  Journal of Asthma.  41:319-326.
(12) Okamoto, M et al.  2000.  Effects of dietary supplementation with n-3 fatty acids compared with n-6 fatty acids on bronchial asthma.  Intern Med.  39(2):107-111
(13) Nagakura et al.  2000.  Dietary supplementation with fish oil rich in omega-3 polyunsaturated fatty acids in children with bronchial asthma.  Eur Resp J.  16(5):861-865.
(14) Beauchamp GK et al.  2005.  Phytochemistry: ibuprofen-like activity in extra-virgin olive oil.  Nature.  437:45-46.

Written by Ani Kowal