Evening primose oil and fish oil are ineffective as supplementary treatment of bronchial asthma.

The effect of daily dietary supplementation with 15 to 20 mL of evening primrose seed oil or fish oil was assessed by comparison with olive oil as placebo in a cross-over study in 29 asthmatics. During 10 weeks of each regimen, the patients kept record of symptoms, peak expiratory flow rates and medication. Plasma and urine TxB2, PGE2, PGF2 alpha and 6 keto-PGF1 alpha and plasma fatty acid composition of plasma cholesterol esters were measured at the end of each treatment period. There were no differences between regimes with regard to peak flow rates, symptoms, or drug consumption. Plasma PGE2 levels increased during the fish oil treatment but there were no changes in other prostanoids in plasma or urine. The fatty acid pattern of plasma cholesterol esters showed significant differences between the supplementation periods. We conclude that moderate doses of evening primrose oil or fish oil are ineffective as a supplementary treatment of bronchial asthma.