Muscle proximate composition of various food fish species and their nutritional significance: A review

Fish (finfish or shellfish) may have health benefits and also contain contaminants, resulting in confusion over the role of fish consumption in a healthy diet. We searched MEDLINE, governmental reports, and meta-analyses, supplemented by hand reviews of references and direct investigator contacts, to identify reports published through April 2006 evaluating (1) intake of fish or fish oil and cardiovascular risk, (2) effects of methylmercury and fish oil on early neurodevelopment, (3) risks of methylmercury for cardiovascular and neurologic outcomes in adults, and (4) health risks of dioxins and polychlorinated biphenyls in fish. We concentrated on studies evaluating risk in humans, focusing on evidence, when available, from randomized trials and large prospective studies. When possible, meta-analyses were performed to characterize benefits and risks most precisely. Modest consumption of fish (eg, 1-2 servings/wk), especially species higher in the n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), reduces risk of coronary death by 36% (95% confidence interval, 20%-50%; P or =5 servings/wk) should limit intake of species highest in mercury levels. Levels of dioxins and polychlorinated biphenyls in fish are low, and potential carcinogenic and other effects are outweighed by potential benefits of fish intake and should have little impact on choices or consumption of seafood (women of childbearing age should consult regional advisories for locally caught freshwater fish). For major health outcomes among adults, based on both the strength of the evidence and the potential magnitudes of effect, the benefits of fish intake exceed the potential risks. For women of childbearing age, benefits of modest fish intake, excepting a few selected species, also outweigh risks.

During the recent decades, awareness towards the role of essential fatty acids in human health and disease prevention has been unremittingly increasing among people. Fish, fish oils and some vegetable oils are rich sources of essential fatty acids. Many studies have positively correlated essential fatty acids with reduction of cardiovascular morbidity and mortality, infant development, cancer prevention, optimal brain and vision functioning, arthritis, hypertension, diabetes mellitus and neurological/neuropsychiatric disorders. Beneficial effects may be mediated through several different mechanisms, including alteration in cell membrane composition, gene expression or eicosanoid production. However, the mechanisms whereby essential fatty acids affect gene expression are complex and involve multiple processes. Further understanding of the molecular aspects of essential fatty acids will be the key to devising novel approaches to the treatment and prevention of many diseases.

Few studies have examined associations of fish consumption with ischemic heart disease (IHD) risk among older adults or how different types of fish meals relate to IHD risk. In a population-based prospective cohort study, usual fish consumption was ascertained at baseline among 3910 adults aged > or =65 years and free of known cardiovascular disease in 1989 and 1990. Consumption of tuna and other broiled or baked fish correlated with plasma phospholipid long-chain n-3 fatty acids, whereas consumption of fried fish or fish sandwiches (fish burgers) did not. Over 9.3 years' mean follow-up, there were 247 IHD deaths (including 148 arrhythmic deaths) and 363 incident nonfatal myocardial infarctions (MIs). After adjustment for potential confounders, consumption of tuna or other broiled or baked fish was associated with lower risk of total IHD death (P for trend=0.001) and arrhythmic IHD death (P=0.001) but not nonfatal MI (P=0.44), with 49% lower risk of total IHD death and 58% lower risk of arrhythmic IHD death among persons consuming tuna/other fish 3 or more times per week compared with less than once per month. In similar analyses, fried fish/fish sandwich consumption was not associated with lower risk of total IHD death, arrhythmic IHD death, or nonfatal MI but rather with trends toward higher risk. Among adults aged > or =65 years, modest consumption of tuna or other broiled or baked fish, but not fried fish or fish sandwiches, is associated with lower risk of IHD death, especially arrhythmic IHD death. Cardiac benefits of fish consumption may vary depending on the type of fish meal consumed.