A total of 98 patients aged between 12 and 25 years were randomized to receive a daily 4 g omega-3 fatty acid supplement (n = 77) or a protein-free soy oil placebo (n = 21) for 24 weeks. Eligible patients had physician-diagnosed asthma, uncontrolled asthma with the use of a daily inhaled corticosteroid controller, and overweight/obesity. The primary outcome was results from the Asthma Control Questionnaire (ACQ), and secondary outcomes were blood leukocyte n3PUFA levels, urinary leukotriene-E4 (uLTE4), spirometry, and asthma-related events.
No evidence that fish oil supplementation affects asthma in overweight patients in #RCT. Should I file this to Archives of RCTs disproving hypotheses generated from retrospective studies, or to the archives of inconclusive studies? #MondayMood #Asthma https://t.co/Sh3hftgxkr pic.twitter.com/7scinoRD6A
— Naftali Kaminski (@KaminskiMed) January 28, 2019
More than 86% of patients completed the trial. The fish oil group had no change in mean ACQ at six months (fish oil group: -0.09 [-0.09, 0.10] vs. control group: -0.18 [-0.42, 0.06], p=0.58). Six-month changes were similar between both cohorts in uLTE (p=0.24), FEV1 percent predicted (p=0.88), and exacerbations (RR=0.92, 95% CI 0.30-2.89). One difference researchers noted, though, is that the fish oil group made fewer asthma-related phone calls to their providers (RR=0.34, 95% CI 0.13-0.86, p=0.02).
— Juan C Ivancevich MD (@Aller_MD) January 26, 2019
“That could be a red herring or it may mean something else,” study author Jason E. Lang, MD, of Duke University, told MedPage Today.
The researchers chose this population because young age and overweight are risk factors for uncontrolled asthma, Lang said.
“We know that obesity is associated with more general inflammation,” he said, adding, “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.”
In their report, the study authors concluded, “In adolescents and young adults with overweight/obesity and uncontrolled asthma, fish oil supplementation at 4g/day increased n3PUFA concentration in peripheral blood monocytes and granulocytes. However, these enhancements did not translate to a measurable reduction in LTE4 production, asthma control, nor most secondary outcomes. These findings do not support a strategy of therapeutic n3PUFA supplementation in these patients with symptomatic asthma.”