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Full Title: Health Effects of Omega-3 Fatty Acids on Cardiovascular Risk Factors and Intermediate Markers of Cardiovascular Disease
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Objectives: To assess the effect of consumption of omega-3 fatty acids on various risk factors and intermediate markers of cardiovascular disease (CVD) in healthy people or people with dyslipidemia, diabetes, or known CVD.
Data Sources: MEDLINE®, EMBASE, Cochrane Central Register of Controlled Trials, Biological Abstracts, and Commonwealth Agricultural Bureau databases were searched for potentially relevant studies.
Review Methods: The researchers analyzed 123 studies that met inclusion criteria (quantification of the amount of fish or omega-3 fatty acid intake, consumption of less than 6 g of omega-3 fatty acid per day, and duration of at least 4 weeks). Information was abstracted about the study design, population demographics, the amount of omega-3 fatty acids (in supplements or diet) or fish consumed, and outcomes. For RCTs, the researchers assessed methodological quality.
Results: The effect of omega-3 fatty acids was examined on a variety of CVD risk factors and on intermediate markers of CVD. The researchers also assessed correlations between long-chain, omega-3 fatty acids intake and tissue phospholipid levels.
Omega-3 fatty acids demonstrated a consistently large, significant effect on triglycerides-a net decrease of 10-33 percent. The effect was dose dependent, generally consistent in different populations, and was generally larger in studies with higher mean baseline triglyceride levels. In contrast to fish oils, the single study of plant-derived alpha-linolenic acid found a net increase in triglycerides. Omega-3 fatty acids had a weaker effect on other serum lipids, such as high-density lipoproteins.
A small beneficial effect was found with fish oil supplementation for blood pressure (reduced about 2 mm Hg), restenosis rates after coronary angioplasty (14 percent reduction), exercise tolerance, and heart rate variability. For other outcomes, including measures of glucose tolerance, the effects of omega-3 fatty acids were either small or inconsistent across studies.
Conclusions: A large, consistent beneficial effect of omega-3 fatty acids was found only for triglyceride levels. Little or no effect of omega-3 fatty acids was found for a variety of other cardiovascular risk factors and markers of cardiovascular disease. The benefits of omega-3 fatty acids on reducing cardiovascular disease are not well explained by the fatty acids' effects on the examined cardiovascular risk factors.
Given the large amount of heterogeneity across studies for the outcomes evaluated, many questions remain about the effect of omega-3 fatty acids in improving potential CVD risk factors and intermediate markers of CVD. Additional research is needed to determine the optimal treatment.
Health Effects of Omega-3 Fatty Acids on Cardiovascular Risk Factors and Intermediate Markers of Cardiovascular Disease
Evidence-based Practice Center: Tufts-New England Medical Center
Topic Nominator: Office of Dietary Supplements, National Institutes of Health
Current as of March 2004