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.