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Review
. 2006 Apr 1;332(7544):752-60.
doi: 10.1136/bmj.38755.366331.2F. Epub 2006 Mar 24.

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

Lee Hooper  1 , Rachel L Thompson, Roger A Harrison, Carolyn D Summerbell, Andy R Ness, Helen J Moore, Helen V Worthington, Paul N Durrington, Julian P T Higgins, Nigel E Capps, Rudolph A Riemersma, Shah B J Ebrahim, George Davey Smith
Affiliations
Review

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

Lee Hooper et al. BMJ. .

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 (3) 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.

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Figures

Fig 1
Fig 1
The selection process for randomised controlled trials (RCTs) and cohort studies on omega 3 fatty acid and health outcomes
Fig 2
Fig 2
Effect of omega 3 fatty acids on mortality. For references see bmj.com
Fig 3
Fig 3
Effect of omega 3 fatty acids on cardiovascular events. For references see bmj.com
Fig 4
Fig 4
Effect of omega 3 fatty acids on the diagnosis of cancer or death from cancer. For references see bmj.com
Fig 5
Fig 5
Effect of omega 3 fatty acids on stroke. For references see bmj.com
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