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Cutting down on omega-6 is better than increasing omega-3
T M McKeever, S A Lewis, P A Cassano, M Ocké, P Burney, J Britton, H A Smit. The relation between dietary intake of individual fatty acids, FEV1 and respiratory disease in Dutch adults. Thorax 2008;63:208-214
Abstract
Background: A reduced dietary intake of n-3 fatty acids, in association with increased n-6 fatty acid intake, has been proposed as a potential aetiological factor for chronic obstructive pulmonary disease (COPD) and asthma. However, the relative importance of individual fatty acids within the n-3 and n-6 categories on this effect has not been widely investigated. We have studied the relation between individual fatty acid intakes, lung function and self-reported respiratory symptoms and diagnoses in a representative sample of more than 13 000 Dutch adults.
Methods: Intake of individual fatty acids was estimated by a food frequency questionnaire and analysed in relation to measures of forced expiratory volume in 1 s (FEV1) and to questionnaire reported wheeze, asthma and COPD symptoms.
Results: After adjusting for confounding, we found no protective association between individual n-3 fatty acid intakes and FEV1. Higher intakes of some n-6 fatty acids were associated with lower FEV1, this effect being most marked for c22:4 n-6 docosatetraenoic acid (reduction in FEV1 between the highest and lowest quintile of intake 54.5 ml (95% CI –81.6 to –27.4)). Most of the n-6 fatty acid effects interacted significantly with smoking, their effects being strongest in current smokers. Individual n-3 fatty acid intakes were generally associated with a higher risk of wheeze in the past year, but otherwise there was little or no association between fatty acid intake and wheeze, doctor diagnosed asthma or other respiratory symptoms.
Conclusions: A high intake of n-3 fatty acids does not appear to protect against COPD or asthma, but a high intake of several n-6 fatty acids is associated with a significant reduction in FEV1, particularly in smokers. These findings indicate that high dietary intake of n-6 fatty acids, rather than reduced n-3 intake, may have an adverse effect on lung health.
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COMMENT: For the last quarter of a century we have been advised to choose veteable oils and margarines in place of traditional fats such as butter. As a consequence, the omega-6 fatty acids which predominate in these vegetable fats have overwhelmed their cousins, the omega-3 fatty acids.
So, more recently, we have been exhorted to increase our intakes of omega-3s to make up for the imbalance between the two. This has led to a much higher intake of these polyunsaturated fatty acids in total — and that is decidedly unhealthy.
And, as this study shows, we don't need to, because it doen't work. Rather thasn increase omega-3s, they say, we should reduce omega-6s. In other words, what we should really do is go back to eating butter and other traditional fats which have the correct proportion of both omega-3 and omega-6
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