Merchants of doubt: the Omega-3 fatty acid study in the NEJM

sardinesIn the New England Journal of Medicine (9 May 2013) the results of The Risk and Prevention Study Collaborative Group on n-3 Fatty Acids in patients with multiple cardiovascular risk factors are published. The authors conclude that in a large general-pratice cohort of patients with multiple cardiovascular risk factors, daily treatment with n-3 fatty acids (n-3FA) did not reduce cardiovascular mortality and morbidity. Study patients received one capsule daily containing 1 g fatty acids with docosahexaenoic acid (DHA) content of < 85%. This result was highly predictable as in several earlier studies is concluded that responsiveness of cardiovascular risk markers is highly dose-dependent. Anti-arrhythmic actions became evident at intakes as low as 200 mg/day, but intakes of 2-3 g per day are needed to cause a meaningful reduction in plasma inflammatory markers, arterial blood pressure and vascular function. (Musa-Velosa et al. Br J Nutr 2011). Studies indicate that n-3FA intakes of approxiamtely 1 gr/day is protective in subjects free of known cardiovascular risks at baseline (ISO et al 2006; He et al. 2004). A dose of 1 g could be considered a minimum target intake, rather than an absolute target, especially in high-risk individuals. Furthermore, cardiovascular benefits will be become clear after prolonged and higher intake, e.g. 1.8 g/day for 5 years (Yokoyama et al. 2005). And there should be a balance between n-3 fatty acids and n-6 fatty acids ( n-3:n6FA balance )

In age-adjusted analyses, fish consumption is inversely associated with the risk of chronic diseases, but this association was attenuated and no longer significant after adjusting for other risk factors and dietary habits.

The Collaborative Group did not measure n-3FA levels in plasma. It is found that significantly higher levels of docosapentaenoic acid (DPA) and lower levels of DHA were found in high-risk individuals. High DPA is linked to a deteriorated cardiovascular risk profile, high DHA with a more favourable (Garneau et al, 2013).

Higher consumption of fish oil (2-3 g/day) can be safe (Mozaffarioan & Rimm JAMA 2006) and is beneficial in reducing systemic blood pressure and systemic vascular resistance, lowering resting heart rate and improves left ventricular diastolic function. General practitioners and cardiologists could conclude, based on the results of the cohort study by The Risk and Prevention Study Collaborative Group, that recommandation of consumption of fish (oil) to high risk patients is useless, but a higher dose could be benificial. Consumption of fish (oil) should be one the aspects of a complex change in lifestyle for reducing cardiovascular morbidity and mortality.

Obviously this study was published to promote statines and to ridicule more natural methods of lowering the risk factors for cardiovascular diseases. I don’t like this, bad science. Merchants of doubts.

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