Oily Fish Reduces Airway Inflammation in Asthmatic Children

Childhood asthma is the most common respiratory disorder worldwide, being associated with increased morbidity and a decreased quality of life.  Omega-3 fatty acids have anti-inflammatory and immunomodulating properties; however, their efficacy in asthma is controversial.

Regularly eating oily fish can help to reduce airway inflammation in children with asthma, according to the results of a study headed by researchers at La Trobe University in Melbourne. The six-month study in children with mild asthma, found that adding omega-3 fatty acid-rich fish such as salmon, trout, and sardines to a healthy Greek Mediterranean diet led to a significant reduction in bronchial inflammation.

Reporting their results in the Journal of Human Nutrition and Dietetics, the researchers, headed by Maria Papamichael, at La Trobe University’s department of rehabilitation, nutrition & sport, say additional trials should now be carried out to corroborate the findings. “We already know that a diet high in fat, sugar, and salt can influence the development and progression of asthma in children and now we have evidence that it’s also possible to manage asthma symptoms through healthy eating,” Papamichael commented. “Fatty fish is high in omega-3 fatty acids which have anti-inflammatory properties. Our study shows eating fish just twice a week can significantly decrease lung inflammation in children with asthma.”

The team described the trial in a paper titled, “Efficacy of a Mediterranean diet supplemented with fatty fish in ameliorating inflammation in paediatric asthma: a randomised controlled trial.”

Childhood asthma is the most common respiratory disorder worldwide, the authors write, and Global Initiative for Asthma estimates suggest that by 2025 there will be an additional 100 million people with asthma worldwide. “Asthma is the most common respiratory disease in young people and one of the leading reasons for hospitalizations and trips to emergency for children,” noted associate professor Bircan Erbas, Ph.D., an expert in asthma and allergies at La Trobe’s School of Psychology and Public Health, who co-supervised the trial. “Unfortunately, the rate of asthma worldwide remains high. It is imperative that we identify new therapies that we can use alongside conventional asthma medications.”

Asthma is caused by genetic and environmental factors, and research has linked disease risk with factors including smoking, pollution, pet hair, house dust mites, mold, and diet. Prior studies have found that diets high in fat, processed foods, sugar, and salt can increase the risk and prevalence of asthma in children and adolescents, the authors continue. Conversely, other research has found that asthma is less prevalent in regions where people commonly eat a Mediterranean diet that is (broadly) rich in vegetables, fruits, unrefined cereals, bread, legumes, and olive oil, and low in meat and dairy.

Studies have also highlighted the importance to health of balancing the ratio of omega-6 to omega-3 fatty acids in the diet. “ … a high omega-6:omega-3 fatty acid ratio can promote the pathogenesis of chronic diseases including asthma,” the authors write. “Specifically, a ratio of 5:1 (as in Mediterranean diets) had a beneficial effect on patients with asthma, whereas a ratio of greater than 10:1 (as in common in Western diets) had adverse consequences. Thus, an optimal ratio of these two fatty acids and a high intake of omega-3 fatty acids might have prophylactic potential with respect to asthma symptoms.”

There are no universal dietary guidelines for asthma, and what isn’t yet known is whether fish-derived omega-3 fatty acids can have any benefit. To investigate this further the team designed a study to investigate the effectiveness of a Mediterranean diet supplemented with omega 3-containing oily fish, on factors such as airway inflammation, in children with asthma. The study involved 64 children aged 5–12 years who had mild asthma, and were living in Greece. The participants were split into two groups. One group continued to eat their regular, Mediterranean-type Greek diet, and the other was instructed to include two meals of cooked oily fish (at least 150 grams) daily for six months as part of their Mediterranean diet. Questionnaires were completed to evaluate adherence to diet, asthma control, and physical activity.

At the end of the six months, and after adjusting for factors such as age, body mass index, and regular physical exercise, the team found that the addition of oily fish to the diet resulted in significant reductions in bronchial inflammation, measured as exhaled nitric oxide (FeNO). The 14 units reduction was higher than the 10 units cut-off for significance. There was also a greater (though not statistically significant) reduction in the use of anti-leuktriene medication among children consuming a Mediterranean diet rich in oily fish, which the authors say also warrants further exploration.

“To our knowledge, this is the first clinical trial investigating the effect of high omega-3 ‘fatty’ fish intake added to a Mediterranean diet in children with ‘mild’ asthma,” the authors concluded. “Few studies have examined the effect of fatty fish in asthma and the present study adds to the existing evidence … our findings suggest that a Mediterranean diet supplemented with fatty fish might be a potential nonpharmacological strategy to combat airway inflammation.”

The team said their findings have important public health implications because it is relatively easy and inexpensive to change dietary habits in “real-life” situations. “Following a traditional Mediterranean diet that is high in plant-based foods and oily fish could be an easy, safe, and effective way to reduce asthma symptoms in children,” commented co-researcher and head of La Trobe’s School of Allied Health, Catherine Itsiopoulos, Ph.D.