Fat v fibre
Saturated fats and asthma
Asthma is a condition of airway narrowing due, in part, to inflammation and swelling in the airways in your lungs. The degree of airway swelling can be indicated by the number of eosinophils (a type of white blood cell which contributes to the inflammation and swelling) circulating in the body and in mucus - the higher the number of eosinophils, the higher the level of airway swelling.
It has been found that for people with asthma, a diet high in fat is associated with an increase in the number of airway eosinophils1, whilst one high fat meal can result in airway swelling within hours2. Another study showed a direct link between the amount of hamburgers (a food typically high in saturated fat) eaten and asthma symptoms - the more hamburgers eaten, the more asthma symptoms3.
Extra body weight and the impact on asthma
A diet high in saturated fat can be very energy dense (contains lots of kilojoules) and can increase the risk of a person becoming overweight or obese. Being overweight or obese is associated with many conditions such as diabetes, cardio-vascular disease, some cancers and mental health problems4, but it can also affect asthma. A person who is overweight or obese is more likely to have asthma compared to a person in the healthy weight range5.
For people who already have asthma, being obese can cause asthma to be more difficult to control and harder to manage6. For those people with severe asthma, even a small weight increase of a few kilograms can result in poorer asthma control and the need for more oral steroids 7. Even though medication is the mainstay of asthma management, aiming to maintain a healthy weight may help to improve control of asthma symptoms.
Research has demonstrated that if you are overweight or obese, weight loss of as little as 5-10% of your current body weight is enough to reduce asthma symptoms8.
Can diet improve asthma?
Emerging data from recent research in Australia has indicated that a diet high in fibre, in particular inulin, can reduce airway inflammation and improve lung function9. The study involved 17 people with asthma at Newcastle University’s Centre for Healthy Lungs taking a daily soluble fibre supplement containing inulin.
Although further funding is required to conduct a larger, longer term trial to determine if this could be used as part of a treatment regimen for asthma, biomedical science professor Lisa Wood suggested anyone could trial increasing fibre in their diet. She told ABC news that, “Soluble fibre is present in high concentrations in fruit and vegetables and wholegrains, so if people are wanting to try this strategy, then certainly increasing those healthy foods in the diet is a sensible approach.”10
Including fibre in your diet can also assist with weight loss as high food fibre foods are predominantly low energy and filling. Fibre rich foods are plant based such as fruit and vegetables. Aim for 2 serves of fruit and 5 serves of vegetables each day to boost fibre.
How can you help your asthma?
- Minimise intake of processed and take-away foods high in saturated fat 11,12
- Maintain a healthy weight. If you are overweight or obese, aim for a 5-10% weight loss
- Consume foods rich in fibre like fruit and vegetables
- Berthon, BS, Macdonald-Wicks, LK, Gibson, PG, Wood, LG 2013, Investigation of the association between dietary intake, disease severity and airway inflammation in asthma’, Respirology, vol. 18, pp. 44-454, doi 10.1111/resp.12015.
- Wood, LG, Manohar, L, Garg, ML, Gibson, PG 2011, ‘A high-fat challenge increases airway inflammation and impairs bronchodilator recovery in asthma’, American Academy of Allergy, Asthma and Immunology, vol. 127, pp. 1133-40, doi: 10.1016/j.jaci.2011.01.036.
- Wickens, K, Barry D, Friezema A, Rhodius R, Bone N, Purdie G, Crane J 2005, ‘Fast foods – are they a risk factor for asthma’, Allergy, vol. 60, pp 1537-1541, doi
- Australian Government Preventative Health Taskforce 2009, ‘AUSTRALIA: THE HEALTHIEST COUNTRY BY 2020’, retrieved 21 April 2017, http://www.health.gov.au/internet/preventativehealth/publishing.nsf/Content/E233F8695823F16CCA2574DD00818E64/$File/obesity-jul09.pdf
- Deuther, DA, Sutherland, RE 2007, ‘Overweight, Obesity, and Incident Asthma’, American Journal of Respiratory and Critical Care Medicine, vol. 175, pp. 661-666, doi: 0.1164/rccm.200611-1717OC
- Nan, LV, Xiao, L, Ma, J 2015, ‘Weight Management Interventions in Adult and Pediatric Asthma Populations: A Systematic Review’, Journal of Pulmonary and Respiratory Medicine vol. 5, no. 232, doi 10.4172/2161-105X.1000232
- Tmirah Haselkorn, T, Fish, JE, Chipps, BE, Miller, DP, Chen, H, Weiss, SC 2009, Effect of weight change on asthma-related health outcomes in patients with severe or difficult-to-treat asthma, Respiratory Medicine, vol. 103, pp. 274-283, doi: 10.106/j.rmed.2008.08.010
- Scott, HA, Gibson, PG, Garg, ML, Pretto, JJ, Morgan, PJ, Callister, R, Wood, LG, 2013, Dietary Restriction and Exercise Improve Airway Inflammation and Clinical Outcomes in Overweight and Obese Asthma: A Randomised Trial, Clinical and Experimental Allergy, vol, 43, no. 1, pp. 36-49, doi 10.1111/cea.12004.
- Halnes, I, Baines, K.J, Berthon, BS, MacDonald-Wicks LK, Gibson, PG, Wood, LG 2017, Soluble Fibre Meal Challenge Reduces Airway Inflammation and Expression of GPR43 and GP41 in Asthma, Nutrients, vol. 9, no. 1, pp. 57, doi 10.3390/nu9010057
- Kearney, Justine. 27 Mar 2017, Study shows fibre supplements could be used as asthma treatment. ABC News Online retrieved 5 May 2017 http://www.abc.net.au/news/2017-03-27/study-shows-fibre-supplements-could-treat-asthma/8388564
- National Asthma Council Australia 2015, Clinical Issues Food, Australian Asthma Handbook, version 1.1, retrieved 4 May 2015, <https://www.asthmahandbook.org.au/uploads/575a52993d075.pdf>
- Australian Government National Health and Medical Research Council 2013, ‘Australian Dietary Guidelines’, retrieved 4 May 2017, < https://www.nhmrc.gov.au/_files_nhmrc/file/your_health/healthy/nutrition/n55a_australian_dietary_guidelines_summary_131014_1.pdf>