We have known about the anti-inflammatory and cardiovascular protective qualities of EPA and DHA (essential fatty acids common in cold water fish and other sources) since I began in practice in the late 70’s and early 80’s. These benefits were confirmed over the next 30 years with thousands of studies.
A recent study [Arch Intern Med. 2012 Apr 9 Efficacy of Omega-3 Fatty Acid Supplements (Eicosapentaenoic Acid and Docosahexaenoic Acid) in the Secondary Prevention of Cardiovascular Disease] disputes this. This review out of South Korea looked at controlled double blind studies and concluded that the evidence was insufficient to support and claim of reducing any effect of heart disease including all-cause mortality, sudden cardiac death, myocardial infarction, congestive heart failure, or transient ischemic attack and stroke.
It is important to keep in mind that the scientific community did not rush to the conclusion that these essential fatty acids were beneficial. The conclusion was based on epidemiological and observational studies as well as clinical trials looking at a variety of cardiovascular disease outcomes.
Experts have pointed out that this particular meta-analysis cherry-picked 14 randomized clinical trials (RCTs), most of which were small, short-term studies (less than one year of follow-up), leaving out other RCTs of longer length and greater relevance, all observational studies, and three well-respected systematic reviews designed to look specifically at CVD outcomes. For example, two large trials not included in this meta-analysis demonstrated significant benefits of fish oil supplementation. Search GISSI-Prevenzione and GISSI-Heart Failure trials. These studies showed a significant advantage of using EPA/DHA to combat fatal cardiovascular disease.
Science is a process and this one analysis is not a very good one and will not add much to our knowledge.