Abstract
Fish and commercially available fish oil preparations are rich sources of long-chain omega-3 polyunsaturated fatty acids. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are the most important fatty acids in fish oil. Following dietary intake, these fatty acids get incorporated into the cell membrane phospholipids throughout the body, especially in the heart and brain. They play an important role in early brain development during infancy, and have also been shown to be of benefit in dementia, depression, and other neuropsychiatric disorders. Early epidemiologic studies show an inverse relationship between fish consumption and the risk of coronary heart disease. This led to the identification of the cardioprotective role of these marine-derived fatty acids. Many experimental studies and some clinical trials have documented the benefits of fish oil supplementation in decreasing the incidence and progression of atherosclerosis, myocardial infarction, heart failure, arrhythmias, and stroke. Possible mechanisms include reduction in triglycerides, alteration in membrane fluidity, modulation of cardiac ion channels, and anti-inflammatory, anti-thrombotic, and anti-arrhythmic effects. Fish oil supplements are generally safe, and the risk of toxicity with methylmercury, an environmental toxin found in fish, is minimal. Current guidelines recommend the consumption of either one to two servings of oily fish per week or daily fish oil supplements (around 1 g of omega-3 polyunsaturated fatty acids per day) in adults. However, recent large-scale studies have failed to demonstrate any benefit of fish oil supplements on cardiovascular outcomes and mortality. Here, we review the different trials that evaluated the role of fish oil in cardiovascular diseases.
Highlights
Cardiovascular disease (CVD) is a leading cause of death in the United States [1]
The possible cardioprotective role of fish consumption was first identified in the early studies of Greenland’s Inuit population who were found to have a low incidence of myocardial infarction (MI) compared to their Danish counterparts
Large doses of fish oil interfere with the synthesis of very low-density lipoprotein (VLDL) via inhibition of sterol receptor element-binding protein-1c
Summary
Cardiovascular disease (CVD) is a leading cause of death in the United States [1]. despite extensive advances in our knowledge of nutritional options in the prevention and therapy of CVD, the benefits of dietary fish and fish oil supplementation on CVD remains debatable. The benefit was attributed to the high fish consumption by the Inuits [2,3] This was followed by nearly four decades of research, including animal studies, epidemiological studies, randomized controlled trials (RCTs), meta-analyses of epidemiological cohort studies, and trial meta-analyses. Many of these studies demonstrated the cardioprotective effects of fish consumption and fish oil supplementation [4,5,6,7,8,9,10]. The rising amount of evidence led to recommendations regarding consumption of seafood/fish and/or their dietary supplementation with ω-3 PUFA from the Food and Drug Administration (FDA) [11]. We conclude by providing possible reasons for the conflicting evidence and recommendations regarding the dietary intake of fish and fish oil supplements
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