A systematic review from the Agency for Healthcare Research and Quality (AHRQ) found insufficient evidence regarding the effect of or association between omega 3 fatty acids and clinical or intermediate outcomes.
The researchers also said there was a low strength of evidence or no association between omega 3 fatty acids and stroke, death or MI. The AHRQ published the results online on Aug. 12.
Examples of omega 3 fatty acids include marine oils such as eicosapentaenoic acid and docosahexaenoic acid and alphalinolenic acid (ALA).
The researchers mentioned the topic of the association between omega 3 fatty acids and cardiovascular disease has been controversial since the AHRQ published its first systematic review in 2004. They said that statins, antihypertensives and low-dose aspirin act on metabolic and biochemical pathways that omega 3 fatty acids also impact, so omega 3 fatty acids may not have cardiovascular benefits.
For this review, they conducted literature searches of studies from 2002 to June 2015 and also included studies from original reviews that met current eligibility criteria. They selected 98 studies, including 61 randomized controlled trials and 37 longitudinal observational studies.
An analysis of the randomized trials found that marine oil supplementation increased high-density lipoprotein cholesterol and low-density lipoprotein cholesterol by 2 mg/dL or less and decreased trigyclerides. The association was found in healthy people and people with an increased risk for cardiovascular disease.
In addition, the randomized trials showed that marine oil supplements did not change the risk of major adverse cardiovascular events, all-cause death, sudden cardiac death, coronary revascularization or atrial fibrillation. The observational studies showed that higher intake of fish high in omega 3 fatty acids might decrease the risk of ischemic stroke in healthy adults.
Further, whereas the randomized trials showed no benefit for omega 3 fatty acids in reducing cardiovascular death and stroke, the observational studies found some possible benefits.
The researchers added that there was insufficient evidence comparing marine oils and ALA intake on cardiovascular disease outcomes.
“As national dietary patterns shift and new processed foods are introduced into the marketplace, food composition tables used to analyze food frequency questionnaire data need to be updated to ensure accurate estimation of (omega 3 fatty acids and other nutrient) intake,” the researchers wrote. “Similar to trial registries, a data repository for raw observational study data would greatly improve the transparency of data analyses (potentially reduce both reporting and publication biases) and the appropriateness and methodology of meta-analytical techniques for pooling observational studies. An individual participant-level meta-analysis of observational studies of marine oils could address limitations of the study-level meta-analyses that are currently feasible.”