Fish Oil Flops for Asthma Control in Overweight Youth

Fish oil supplementation was not associated with improvements in asthma-related outcomes among overweight/obese teens and young adults with uncontrolled asthma in randomized trial.

Six months of treatment with 4 g/day of fish oil did not improve self-reported asthma control or breathing test outcomes or reduce urgent care visits and severe asthma exacerbations relative to soybean-oil placebo, reported Jason E. Lang, MD, of Duke University, and colleagues in Annals of the American Thoracic Society.

While several studies have linked consumption of cold-water fish rich in omega-3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid to a lower incidence of asthma, research exploring the possible impact of fish oil supplementation on asthma symptoms has been limited.

Both obesity and adolescent age are risk factors for poor asthma control, said Lang, and this is one reason obese and overweight teens and young adults were chosen for the study.

“We know that obesity is associated with more general inflammation,” he told MedPage Today, adding that since omega-3 fatty acids in fish oil have anti-inflammatory properties, the hypothesis was that supplementation with fish oil might have therapeutic benefits in obesity-related asthma.

“We don’t really know why obesity is associated with worse asthma control, but it has been suggested that greater circulating inflammation would prime the lung and airways to be more hyperactive,” he said.

The so-called NOOA trial is one of the largest to date to examine omega 3 supplementation with the primary outcome of improving asthma outcomes.

The study included 98 subjects ages 12-25 who were overweight or obese with uncontrolled asthma.

The study participants were randomized 3:1 to take supplements of omega-3 fatty acid or soy oil as control for 24 weeks. Primary outcomes were asthma symptoms, which were self reported through the Asthma Control Questionnaire (ACQ). Secondary outcomes included blood leukocyte n3PUFA levels, urinary leukotriene-E4, spirometry, and asthma-related events.

A total of 77 study participants were randomized to take the fish oil supplement and 21 were randomized to the control arm of the study. More than 86% of study subjects completed all visits and asthma and demographic characteristics were similar for both treatment groups.

Participants in the fish oil arm of the study showed elevations in blood omega-3 levels, which suggested compliance with treatment, Lang said.

But no significant differences were seen between the two groups in asthma control and lung function measures and changes at 3 and 6 months during the intervention period. Specifically, fish oil supplements did not significantly alter mean ACQ change at 6 months, and FEV₁ percent predicted and exacerbation risk were also similar in both groups.

Fish oil supplementation did appear to impact one asthma symptom outcome, however.

“[Study participants] who took the fish oil made fewer calls to their physicians related to asthma symptoms,” Lang told MedPage Today. “That could be a red herring or it may mean something else.”

The researchers are currently analyzing data from the study to determine if fish oil supplementation affected circulating inflammatory markers.

Participants with a variant of the gene ALOX5 (n=93), which is associated with reduced response to anti-leukotriene drugs, did not respond to fish oil supplements.

Study limitations cited by the researchers included the possibility that the study was too small or that treatment length was too short to show a treatment effect, and/or the fish oil dosage was not large enough to reduce leukotriene production and improve asthma control “in the right population.”

“Our population was mostly sedentary,” the researchers wrote. “Future studies at this dose may yield better efficacy focusing on patients with exercise-induced symptoms or those who report activity limitation.”