Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review

Abstract

Objective To review systematically the evidence for an effect of long chain and shorter chain omega 3 fatty acids on total mortality, cardiovascular events, and cancer. Data sources Electronic databases searched to February 2002; authors contacted and bibliographies of randomised controlled trials (RCTs) checked to locate studies. Review methods Review of RCTs of omega 3 intake for ≥ 6 months in adults (with or without risk factors for cardiovascular disease) with data on a relevant outcome. Cohort studies that estimated omega 3 intake and related this to clinical outcome during at least 6 months were also included. Application of inclusion criteria, data extraction, and quality assessments were performed independently in duplicate. Results Of 15 159 titles and abstracts assessed, 48 RCTs (36 913 participants) and 41 cohort studies were analysed. The trial results were inconsistent. The pooled estimate showed no strong evidence of reduced risk of total mortality (relative risk 0.87, 95% confidence interval 0.73 to 1.03) or combined cardiovascular events (0.95, 0.82 to 1.12) in participants taking additional omega 3 fats. The few studies at low risk of bias were more consistent, but they showed no effect of omega 3 on total mortality (0.98, 0.70 to 1.36) or cardiovascular events (1.09, 0.87 to 1.37). When data from the subgroup of studies of long chain omega 3 fats were analysed separately, total mortality (0.86, 0.70 to 1.04; 138 events) and cardiovascular events (0.93, 0.79 to 1.11) were not clearly reduced. Neither RCTs nor cohort studies suggested increased risk of cancer with a higher intake of omega 3 (trials: 1.07, 0.88 to 1.30; cohort studies: 1.02, 0.87 to 1.19), but clinically important harm could not be excluded. Conclusion Long chain and shorter chain omega 3 fats do not have a clear effect on total mortality, combined cardiovascular events, or cancer.

Inclusion of fish or fish oil in weight-loss diets for young adults: effects on blood lipids

“…[29][30][31][32][33] However, the benefits of LC n-3 PUFAs on cardiovascular health are still a matter of debate. 34 The TG-lowering effects of LC n-3 PUFAs are well documented. 9,35,36 The hypotriacylglycerolemic effects of LC n-3 PUFAs were apparent in this study, where the greatest reduction in TG concentration was seen in the group receiving the largest amount of LC n-3 PUFAs.…”

n-3 fatty acids and cardiovascular disease

“…Based upon a high quality meta-analysis of 41 cohort studies (including more than 563 218 participants) and 48 randomized intervention trials, in which 36 913 participants with and without cardiovascular disease received n-3 PUFA for at least 6 months, Hooper et al 18 concluded that n-3 PUFA do not have a clear effect on total mortality or combined cardiovascular events.…”

Meta-analysis of the effects of n-3 polyunsaturated fatty acids on lipoproteins and other emerging lipid cardiovascular risk markers in patients with type 2 diabetes

“…of cardiovascular mortality in high-risk and general populations [1], although recent trials [2,3] and a metaanalysis [4] have cast doubt on the strength of this evidence. There are limited data about the potential benefits for people with type 2 diabetes [5,6], but two prospective cohort studies among women showed that the risk of coronary heart disease is much lower among women with type 2 diabetes who consume n-3 PUFA [5,7].…”