Introduction
Over the past few decades, there has been a growing interest in the therapeutic properties of fish oil (Iwamoto, Ayers and Mahon 5). A report in 1976 indicated that people who consumed high amounts of fish oil in Greenland had a lowered chance of developing cardiovascular problems (Venturi 4). Clinical trials were conducted with results showing a significant reduction in mortality cases associated with cardiovascular diseases. The sudden reduction in deaths resulting from cardiac diseases led to the increased interest in the potential anti-arrhythmic properties of fish oil (Leon, Shibata and Sivakumaran 1).
Recent fish oil studies conducted on patients with cardiac defibrillators have not shown any immediate positive patient outcomes. This might have been due to various methodological challenges and the use of different formulations of fish oil such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). This “might confer a different effect on stabilizing the membrane by challenging its physical, electrical, and chemical properties” (Leon, Shibata and Sivakumaran 1, par. 2). Thus this study sought to evaluate the Different effects of EPA and DHA on deaths that occur due to cardiac diseases. The researchers hypothesized that the use of fish oil causes a significant reduction in cardiac-related deaths.
Methodology
The study made use of the protocols described by Cochrane Collaboration for systematic reviews. Extensive research data on cardiac problems and fish oil was collected from several resources and reviewed. The researchers updated their data searches to eliminate the chances of bias. Different researches that had been conducted to test fish oil as a dietary supplement were also included in the review.
The desired “primary outcomes were the arrhythmic endpoints of the appropriate implantable cardiac defibrillator intervention and sudden cardiac death” (Leon, Shibata and Sivakumaran 2, par. 3). All deaths related to cardiac causes were categorized as secondary outcomes (Leon, Shibata, and Sivakumaran 2). Subgroup analysis focused on the effects of fish oil in patients with coronary artery disease or myocardial infarction (Leon, Shibata and Sivakumaran 2).
The research team divided itself into groups that were responsible for the accomplishment of different tasks. One group identified sources and reviewed the abstracts. One member acted as a mediator to iron out inconsistencies. The third group consisting of two investigators entered the data into forms “systematically and independently on the outcomes of interest, inclusion criteria, the risk of bias and interventions” (Leon, Shibata and Sivakumaran 2, par. 4). The fourth group consisting of two reviewers carried out an independent assessment of the quality of every study using a Jadad criteria form (Leon, Shibata and Sivakumaran 2).
The agreement of different sets of data from different reviewers was measured using Kappa analysis and heterogeneity was measured using chi-square and the T-test. Meta-regression analysis was used to establish the existence of dose-response for both DHA and EPA. Death outcome due to cardiac causes was taken to be the statistically significant outcome (Leon, Shibata and Sivakumaran 2). The risk posed by fish oil to patients was assessed in comparison to placebo.
Results
Studies that did not make use of randomized trials were excluded. Those with duplicate data were also excluded leaving the researchers with a total of 12 studies. Out of the 12 studies reviewed five had a score of 5 for methodological quality on the Jadad scale, four of them had 4, two with 3 and one scored 2 (Leon, Shibata and Sivakumaran 3). It was established “that fish oil supplementation reduced the risk of appropriate implantable cardiac defibrillator intervention by a non-significant 10%” (Leon, Shibata and Sivakumaran 3, par. 2). The results indicated an overall non-significant dose-response relation for DHA and EPA on the reduction or cardiac-related deaths (Leon, Shibata and Sivakumaran).
The researchers concluded that the use of fish oil as a supplement reduced the number of deaths by a significant margin when all cardiac cases were considered. However, it had no significant effect on arrhythmias. Thus further trials are required to verify whether the reduction in cardiac mortality rates is a result of reduced arrhythmias or due to a delay in the progression of coronary artery diseases (Stone 5).
Comments and other findings
As discussed above, the studies show that fish oil is beneficial in reducing cardiac associated deaths. However, there are no established doses as to how much fish oil a given patient should use. However, one can use daily doses described in the studies reviewed. It remains to be established if fish has any effect on arrhythmic events (Stone 5).
Other studies have also shown that fish oil reduces the risk of heart diseases (Venturi 3). Several epidemiological studies have indicated that people “who eat fish sometimes every week had a lower coronary heart disease mortality rate than those who don’t eat fish” (Venturi 4, par. 5). The following mechanism of action has been suggested: a comprehensive review of human studies indicates that omega -3 fatty acids that are derived from fish oil lead to a reduction in serum triglyceride levels by up to 30 percent (Venturi 6).
This is usually accompanied by an increase in LDL cholesterol levels to up to 10 percent and HDL cholesterol to 3% (Iwamoto, Ayers and Mahon 4). Omega-3 fatty acids are also found to decrease the ability of platelets to aggregate resulting in the elongation of bleeding times. Omega-3 fatty acids were also shown to reduce blood pressure in hypertensive patients (Stone 5).
Works cited
Iwamoto, Martha, et al. “Epidemiology of Seafood-Associated Infections in the United States.” clin. microbiol (2010): 399-411. Print.
Leon, Hernando, et al. “Effect of fish oil on arrhythmias and mortality: systematic review.” BMJ (2009): 2931. Web.
Stone, Nixon. “Fish Consumption, fish oil, lipids, and coronary heart disease.” Circulation (1996): 2337-2340. Print.
Venturi, Coochi. “Iodide, antioxidant function and Omega-6 and Omega-3 fatty acids: a new hypothesis of a biochemical cooperation?.” Progress in Nutrition (2000): 15-19. Print.