Omega 3 fatty acids for prevention and treatment of cardiovascular disease

Abstract

Background It has been suggested that omega 3 (W3, n-3 or omega-3) fats from oily fish and plants are beneficial to health. Objectives To assess whether dietary or supplemental omega 3 fatty acids alter total mortality, cardiovascular events or cancers using both RCT and cohort studies. Search methods Five databases including CENTRAL, MEDLINE and EMBASE were searched to February 2002. No language restrictions were applied. Bibliographies were checked and authors contacted. Selection criteria RCTs were included where omega 3 intake or advice was randomly allocated and unconfounded, and study duration was at least six months. Cohorts were included where a cohort was followed up for at least six months and omega 3 intake estimated. Data collection and analysis Studies were assessed for inclusion, data extracted and quality assessed independently in duplicate. Random effects meta-analysis was performed separately for RCT and cohort data. Main results Forty eight randomised controlled trials (36,913 participants) and 41 cohort analyses were included. Pooled trial results did not show a reduction in the risk of total mortality or combined cardiovascular events in those taking additional omega 3 fats (with significant statistical heterogeneity). Sensitivity analysis, retaining only studies at low risk of bias, reduced heterogeneity and again suggested no significant effect of omega 3 fats. Restricting analysis to trials increasing fish-based omega 3 fats, or those increasing short chain omega 3s, did not suggest significant effects on mortality or cardiovascular events in either group. Subgroup analysis by dietary advice or supplementation, baseline risk of CVD or omega 3 dose suggested no clear effects of these factors on primary outcomes. Neither RCTs nor cohorts suggested increased relative risk of cancers with higher omega 3 intake but estimates were imprecise so a clinically important effect could not be excluded. Authors’ conclusions It is not clear that dietary or supplemental omega 3 fats alter total mortality, combined cardiovascular events or cancers in people with, or at high risk of, cardiovascular disease or in the general population. There is no evidence we should advise people to stop taking rich sources of omega 3 fats, but further high quality trials are needed to confirm suggestions of a protective effect of omega 3 fats on cardiovascular health. There is no clear evidence that omega 3 fats differ in effectiveness according to fish or plant sources, dietary or supplemental sources, dose or presence of placebo.

Dietary fatty acids and cardiovascular disease

“…This trial has been criticized as being unblinded and for the nature of the EPA-rich fish oil (Marik and Varon, 2009). Hooper et al (2004) note that excluding this one trial alters the conclusions of the analysis and supports a beneficial effect of n-3 PUFA. A contemporary systematic review by Wang et al (2006) concluded that consumption of very long chain n-3 PUFA from fish or fish oil reduces overall mortality, cardiac mortality and sudden death, with the evidence being considerably stronger for secondary prevention (in subjects who have already suffered a CVD event) rather than primary prevention.…”

“…Such findings have spawned a large number of cohort and interventional studies aimed at evaluating the possible benefits of consuming very long chain n-3 PUFA (either through consuming fish or fish oil supplements) on CVD mortality and morbidity. Hooper et al (2004 and carried out a systematic review of 48 randomized control trials and 41 cohort studies investigating the impact of n-3 PUFA on total mortality and CVD events. Their somewhat surprising conclusion was that there was no clear evidence that dietary or supplemental n-3 PUFA altered total mortality or combined CVD events either in people with, or at high risk of, CVD or in the general population.…”

“…A large cohort study, following 45 722 men over a period of 14 years, concluded that consumption of plant-derived n-3 PUFA (largely ALA) reduced CHD risk, particularly when intake of marine-derived n-3 PUFA is low (Mozaffarian et al, 2005). However, neither the systematic review of Hooper et al (2004 and nor that of Wang et al (2006) found any specific benefit of ALA consumption. A further recent cohort study of 20 069 men and women, followed between 8 and 13 years, has also failed to demonstrate any relationship between ALA intake and CHD risk (de Goede et al, 2011).…”

Atorvastatin in Factorial with Omega-3 EE90 Risk Reduction in Diabetes (AFORRD): a randomised controlled trial

“…Omega-3 (n-3) polyunsaturated fatty acids (PUFA) are an alternative triacylglycerol-lowering therapy; there is strong epidemiological evidence suggesting favourable outcomes in people with type 2 diabetes with high omega-3 PUFA intake [16] and improvements in CVD-risk-factor profiles [17,18]. Studies involving wider populations have been less supportive [19], and a prospective primary-care trial is required to establish whether omega-3 PUFA, alone or with a statin, can improve risk-factor levels and reduce estimated CVD risk as a prelude to cardiovascular-outcome studies.…”

Current and Novel Treatments for Ulcerative Colitis

“…8.1 n-3 fatty acids Over the years, dietary n-3 fatty acids have gained a reputation in preventing and treating several disorders including cardiovascular diseases, rheumatoid arthritis and Alzheimer's disease by way of anti-inflammatory, antithrombotic, antiarrythmic, hypolipidemic and vasodilatory activities (101,(106)(107)(108)(109)(110)(111). It has been shown in human and animal studies that these n-3 fatty acids have potent immunomodulatory and anti-inflammatory effects by inhibiting the production of inflammatory mediators, eicosanoids, PGE2 and LTB4 and cytokines, TNF and IL1 (112).…”