A Cochrane review included 4 studies with a total of 91 subjects. Two studies compared omega-3 fatty acids to olive oil controls for a six week treatment period. One study compared a liquid dietary supplement containing omega-3 fatty acids to one without for 6 months. One study compared omega-3 fatty acids and omega-6 fatty acids to a control (capsules with customised fatty acid blends) for 3 months. Only one short-term study (n=19) comparing omega-3 to placebo reported a significant improvement in FEV1, FVC, Shwachman score and reduction in sputum volume in the omega-3 group. Another study (43 participants) demonstrated a significant increase in serum phospholipid essential fatty acid content and a significant drop in the n-6/n-3 fatty acid ratio following omega-3 fatty acid supplementation compared to control. The longer-term study (n=17) demonstrated a significant increase in essential fatty acid content in neutrophil membranes and a significant decrease in the leukotriene B4 to leukotriene B5 ratio in study participants taking omega-3 supplements compared to placebo.
Comment: The quality of evidence is downgraded by imprecise results (few patients) and by indirectness: there was lack of data for many of the outcomes likely to be meaningful to people with or making treatment decisions about cystic fibrosis.