A case-control study of dietary and erythrocyte membrane fatty acids in asthma

Background Epidemiological evidence suggests that increased dietary omega-6 and reduced omega-3 fatty acid intake, may have contributed to the rising prevalence of asthma, but these hypotheses have not been tested in studies comparing both dietary intake and objective measures of polyunsaturated fatty acids. Objective To assess whether a higher intake of omega-6 or a lower intake of omega-3 fatty acids increases the risk of asthma, by measuring dietary fatty acid intake by a food frequency questionnaire (FFQ) and erythrocyte membrane fatty acids, as an objective biomarker of intake. Methods We have compared individual fatty acid intake estimated by FFQ and by mass spectrometry of fasting erythrocyte cell membranes in 89 cases of asthma and 89 community-matched controls. Results The odds of asthma were increased in relation to intake of the omega-3 fatty acids eicosapentaenoic acid (odds ratio (OR) for difference between the 25th and 75th centiles of intake=1.89, 95% CI 1.15-3.11) and docosahexaenoic acid (OR=2.11, 95% CI 1.19-3.74). There was no evidence of any difference in erythrocyte membrane levels of omega-3 fatty acids, while the odds of asthma were reduced in relation to linoleic acid (omega-6) membrane levels (OR=0.45, 95% CI 0.21-0.95). Conclusion These findings suggest that dietary omega-3 fatty acids do not play a major role in protecting against asthma, and that higher levels of erythrocyte membrane linoleic acid are associated with a lower risk of asthma.