Can dietary change help asthmatics to breathe easier? Part II

At the beginning of the week I examined how a Mediterranean diet may be useful in the prevention and easing of asthma symptoms.  Today I wanted to add a little more information on the link between diet and asthma.


Salt consumption has been linked to asthma.  A review(1) of studies found that reducing salt intake may be helpful in reducing the severity of asthma attacks in affected individuals.  One study found that giving salt, an additional 6.1g per day, worsened symptoms in asthmatic patients and increased their use of inhaled steroids.  The authors of this study suggest that a low salt diet (around 5g per day) may have favourable effects in patients with asthma and can reduce the need for anti-asthma drugs(2).  Salt appears to heighten the airways’ response to histamine causing increased airway constriction(3).  Avoiding the addition of salt to food and limiting consumption of processed foods might help to reduce asthma symptoms and is also a good idea for all of us.  Excess salt has been linked to various conditions including high blood pressure, heart disease, cancer, kidney problems, osteoporosis and fluid retention (for more information on salt and health visit Consensus Action on Salt and Health CASH).


Interesting evidence shows that the gut bacteria of healthy infants appears different to those who suffer from allergies, eczema and asthma (known as ‘atopic’ infants).  Atopic infants seem to have a disturbed balance between beneficial and potentially harmful bacteria in their large intestine(4,5,6).  A healthy balance of microorganisms in the digestive system is thought to be essential for the normal development and maturation of the immune system.  In one study, the probiotic Lactobacillus GG was give to pregnant women who had at least one first-degree relative (or partner) with an allergic condition such as atopic eczema, allergic rhinitis, or asthma.  After the birth, the probiotic was also given to the child for 6 months.  Probiotic supplementation significantly reduced risk of early allergic disease in children at high risk (7)


Research in this area is still in the early stages, clinical studies of children and supplement studies in animals do suggest that the exposure to microbes through the digestive system powerfully shapes immune function.  Taking a probiotic or prebiotic supplement during pregnancy, breastfeeding and early childhood could be considered in order to prevent against asthma/allergy development in children.  Some infant milks are already including pre probiotics in their formulation (Always check with a doctor before undergoing any supplementation programme, especially during pregnancy).


Finally I would like to mention food allergies.  If your child suffers from asthma it may be worth taking them to the doctor for a skin-prick test in order to determine whether they suffer from a true food allergy.


Food sensitivity may be an underlying factor in asthma, especially in childhood asthma.  In one study, 91% of children with respiratory allergy improved on a six-week diet that excluded common problem foods including grains and dairy products(8).  And a review(9) found that approximately 5% to 8% of asthma patients have a food allergy that can be confirmed via a food challenge. Identification and elimination of problem foods is often a useful strategy in the management of asthma.  This should always be done under the supervision of a doctor. 


(1)Mickleborough TD & Fogarty A. 2006. Dietary sodium intake and asthma: an epidemiological and clinical review.  International Journal of Clinical Practice.  60:1616-1624.
(2)Medici TC et al.  1993.  Are asthmatics salt-sensitive? A preliminary controlled study. Chest.  Oct;104(4):1138-43
(3)Burney PG et al.  1981.  The effect of changing dietary sodium on the bronchial response to histamine.  Thorax.  44(1):36-41
(4)Kirjavainen PV et al.  2001.  characterizing the composition of intestinal microflora as a prospective treatment target in infant allergic disease.  FEMS Immunol Med Microbiol.  32:1-7. 
(5)Kirjvainen PV et al.  2002.  Aberrant composition of gut microbiota of allergic infants: a target of bifidobcterial therapy at weaning.  Gut.  51:51-55. 
(6)Murch, SH.  2001.  Toll of allergy reduced by probiotics.  Lancet.  357:1057-1059
(7)Kalliomaki M et al.  2001.  Probiotics in primary prevention of atopic disease: a randomised placebo-controlled trial.  Lancet.  357:1076-1079
(8)Ogle KA & Bullock JD.  1980.  Children with allergic rhinitis and/or bronchial asthma treated with elimination diet: a five-year follow-up.  Ann Allergy.  May;44(5):273
(9)Miller A.  2001.  The etiologies, pathophysiology, and alternative/complementary treatment of asthma.  Alternative Medicine Review.  6(1):20-47.


Written by Ani Kowal

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