Oily fish

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The large open-water Atlantic bluefin tuna is an oily fish. Bluefin-big.jpg
The large open-water Atlantic bluefin tuna is an oily fish.
Most small forage fish, like these schooling anchovies, are also oily fish. Anchovy closeup.jpg
Most small forage fish, like these schooling anchovies, are also oily fish.

Oily fish are fish species with oil (fats) in soft tissues and in the coelomic cavity around the gut. Their fillets may contain up to 30% oil, although this figure varies both within and between species. Examples of oily fish include small forage fish such as sardines, herring and anchovies, and other larger pelagic fish such as salmon, trout, tuna, swordfish and mackerel. [1]

Contents

Oily fish can be contrasted with whitefish, which contain oil only in the liver and in much less overall quantity than oily fish. Examples of whitefish are cod, haddock and flatfish. White fish are usually demersal fish which live on or near the seafloor, whereas oily fish are pelagic, living in the water column goes from the bottom.

Oily fish meat is a good source of important fat-soluble vitamins such as Vitamin A and D, and is rich in omega-3 fatty acids (white fish also contain these nutrients but at a much lower concentration). For this reason the consumption of oily fish rather than white fish can be more beneficial to humans, particularly concerning heart diseases such as stroke and ischemic heart disease; [2] however, oily fish are known to carry higher levels of contaminants (such as mercury or dioxin or POPs) than whitefish.[ citation needed ] Among other benefits, studies suggest that the omega-3 fatty acids in oily fish may help improve inflammatory conditions such as arthritis. [3]

Health benefits

Oily fish fillet (salmon - bottom) contrasted with a white fish fillet (halibut - top) Halibut and salmon fillets.jpg
Oily fish fillet (salmon – bottom) contrasted with a white fish fillet (halibut – top)

Dementia

A 1997 study published in Annals of Neurology followed 5,386 elderly participants in Rotterdam. It found that fish consumption decreased the risk of dementia. [4] However, the 2.1-year average follow-up was less than the three years dementia commonly affects people prior to diagnosis. Thus, the study was unclear as to whether fish consumption protected against dementia, or if dementia prevented the participants from wanting more fish. [5]

French research published in 2002 in the British Medical Journal (BMJ) followed 1,674 elderly residents of southern France for seven years, studying their consumption of meat versus seafood and the presence of dementia symptoms. The conclusion was that people who ate fish at least once a week had a significantly lower risk of being diagnosed with dementia over a seven-year period. This study reinforced the Annals of Neurology findings. Because of the longer term, the BMJ study provided stronger evidence of a genuine protective effect. [5] There was a possible confounding factor in that individuals with higher education have both a lower risk of dementia and higher consumption of fish. [6]

Cardiovascular health

Consuming 200–400 g of oily fish twice per week may also help prevent sudden death due to myocardial infarction by preventing cardiac arrhythmia. [7] The eicosapentaenoic acid found in fish oils appears to dramatically reduce inflammation through conversion within the body to resolvins, with beneficial effects for the cardiovascular system and arthritis. [8]

Grilled salmon, an oily fish Thyme and Garlic Grilled Salmon with Mango Salsa, Rosemary Potatoes and Snow Peas (297986190).jpg
Grilled salmon, an oily fish

In 1994, the UK Committee on Medical Aspects of Food and Nutrition Policy recommended that people eat at least two portions of fish per week, one of which should be oily fish.

In 2004 the UK Food Standards Agency published advice on the recommended minimum and maximum quantities of oily fish to be eaten per week, to balance the beneficial qualities of the omega-3 fatty acids against the potential dangers of ingesting polychlorinated biphenyls and dioxins. It reiterated the 1994 guideline of two portions of fish per week including one portion of oily fish, but advised eating no more than four portions per week, and no more than two portions for people who are pregnant, may become pregnant or who are breastfeeding. [9]

The United States Environmental Protection Agency's (EPA) Exposure Reference Dose (RfI) for methylmercury (MeHg) is 0.1 micrograms per kg body weight per day. The corresponding limit of blood mercury is 5.8 micrograms per liter. The restrictions apply to certain oily fish – "marlin, swordfish, shark and, to a lesser extent, tuna". [10] The recommendations on maximum consumption of oily fish were up to four portions (1 portion = 140g, or approx 4.9 ounces) a week for men, boys, and women past childbearing age, and up to two portions a week for women of childbearing age, including pregnant and breastfeeding women, and girls. There is no recommended limit on the consumption of white fish.

The EPA and 2007 U.S. Department of Agriculture guidelines sets a limit only on consumption of fatty fish with greater than one part per million of methylmercury, specifically tilefish, king mackerel, shark and swordfish. [ citation needed ] There are limits, however, for nursing/pregnant women and children under the age of six. This population should completely avoid fish with high risk of mercury contamination (those listed above) and limit consumption of moderate and low-mercury fish to 12 ounces or less per week. [ citation needed ] Albacore tuna should be limited to six ounces or less per week. [ citation needed ]

Omega-3 content

Concerns about contamination, diet or supply have led to investigation of plant sources of omega-3 fatty acids, notably flax, hempseed and perilla oils. Lactating women who supplemented their diet with flaxseed oil showed increases in blood and breastmilk concentration of alpha-linolenic acid and eicosapentaenoic acid but no changes to concentrations of docosahexaenoic acid. [11]

See also

Related Research Articles

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In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food.

Omega−3 fatty acids, also called omega−3 oils, ω−3 fatty acids or n−3 fatty acids, are polyunsaturated fatty acids (PUFAs) characterized by the presence of a double bond three atoms away from the terminal methyl group in their chemical structure. They are widely distributed in nature, being important constituents of animal lipid metabolism, and they play an important role in the human diet and in human physiology. The three types of omega−3 fatty acids involved in human physiology are α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). ALA can be found in plants, while DHA and EPA are found in algae and fish. Marine algae and phytoplankton are primary sources of omega−3 fatty acids. DHA and EPA accumulate in fish that eat these algae. Common sources of plant oils containing ALA include walnuts, edible seeds, and flaxseeds as well as hempseed oil, while sources of EPA and DHA include fish and fish oils, and algae oil.

<span class="mw-page-title-main">Seafood</span> Food from the sea

Seafood is the culinary name for food that comes from any form of sea life, prominently including fish and shellfish. Shellfish include various species of molluscs.

Essential fatty acids, or EFAs, are fatty acids that are required by humans and other animals for normal physiological function that cannot be synthesized in the body.⁠ As they are not synthesized in the body, the essential fatty acids – alpha-linolenic acid (ALA) and linoleic acid – must be obtained from food or from a dietary supplement. Essential fatty acids are needed for various cellular metabolic processes and for the maintenance and function of tissues and organs. These fatty acids also are precursors to vitamins, cofactors, and derivatives, including prostaglandins, leukotrienes, thromboxanes, lipoxins, and others.

α-Linolenic acid Chemical compound

α-Linolenic acid, also known as alpha-linolenic acid (ALA), is an n−3, or omega-3, essential fatty acid. ALA is found in many seeds and oils, including flaxseed, walnuts, chia, hemp, and many common vegetable oils.

<span class="mw-page-title-main">Cod liver oil</span> Dietary supplement derived from liver of cod fish

Cod liver oil is a dietary supplement derived from liver of cod fish (Gadidae). As with most fish oils, it contains the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and also vitamin A and vitamin D. Historically, it was given to children because vitamin D had been shown to prevent rickets, a consequence of vitamin D deficiency.

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<span class="mw-page-title-main">Eicosapentaenoic acid</span> Chemical compound

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<span class="mw-page-title-main">Docosahexaenoic acid</span> Chemical compound

Docosahexaenoic acid (DHA) is an omega−3 fatty acid that is an important component of the human brain, cerebral cortex, skin, and retina. It is given the fatty acid notation 22:6(n−3). It can be synthesized from alpha-linolenic acid or obtained directly from maternal milk (breast milk), fatty fish, fish oil, or algae oil. The consumption of DHA (e.g., from fatty fish such as salmon, herring, mackerel and sardines) contributes to numerous physiological benefits, including cognition. As a component of neuronal membranes, the function of DHA is to support neuronal conduction and to allow the optimal functioning of neuronal membrane proteins (such as receptors and enzymes).

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<span class="mw-page-title-main">Nutrition and pregnancy</span> Nutrient intake and dietary planning undertaken before, during and after pregnancy

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References

  1. ↑ "What's an oily fish?". Food Standards Agency. 24 June 2004. Archived from the original on 10 December 2010.
  2. ↑ "Oily fish helps heart attack victims to live longer - 07 October 1989". New Scientist. 7 October 1989. Retrieved 27 July 2009.
  3. ↑ Kremer JM (2017). "Fish Oil and Inflammation — A Fresh Look". The Journal of Rheumatology. 44 (6): 713–716. doi: 10.3899/jrheum.161551 . PMID   28572471.
  4. ↑ Kalmijn, S.; Launer, L. J.; Ott, A.; Witteman, J. C. M.; Hofman, A.; Breteler, M. M. B. (1997). "Dietary fat intake and the risk of incident dementia in the Rotterdam study". Annals of Neurology. 42 (5): 776–782. doi:10.1002/ana.410420514. hdl: 1765/58975 . PMID   9392577. S2CID   24435633.
  5. 1 2 Barberger-Gateau, P.; Letenneur, L.; Deschamps, V.; Pérès, K.; Dartigues, J. F.; Renaud, S. (2002). "Fish, meat, and risk of dementia: Cohort study". BMJ (Clinical Research Ed.). 325 (7370): 932–933. doi:10.1136/bmj.325.7370.932. PMC   130057 . PMID   12399342.
  6. ↑ Wilkinson, Emma (9 March 2009). "Oily fish dementia boosts queried". BBC News. Retrieved 27 July 2009.
  7. ↑ Leaf, A.; Kang, J. X.; Xiao, Y.-F.; Billman, G. E. (2003). "Clinical prevention of sudden cardiac death by n-3 polyunsaturated fatty acids and mechanism of prevention of arrhythmias by n-3 fish oils". Circulation. 107 (21): 2646–52. doi: 10.1161/01.CIR.0000069566.78305.33 . PMID   12782616.
  8. ↑ Arita, M.; Bianchini F; Aliberti J; Sher A; Chiang N; Hong S; Yang R; Petasis NA; Serhan CN (2005). "Stereochemical assignment, antiinflammatory properties, and receptor for the Omega-3 lipid mediator Resolvin E1". Journal of Experimental Medicine . 201 (5): 713–22. doi:10.1084/jem.20042031. PMC   2212834 . PMID   15753205. Open Access logo PLoS transparent.svg
  9. ↑ "Oily fish advice: your questions answered". Food Standards Agency. 23 June 2004. Archived from the original on 3 December 2013. Retrieved 17 February 2014.
  10. ↑ SACN (2004) Advice on fish consumption: benefits and risks, 20 May 2014, Committee on Toxicity. ISBN   011243083X.
  11. ↑ Francois, C.A.; Connor, S. L.; Bolewicz, L. C.; Connor, W. E. (1 January 2003). "Supplementing lactating women with flaxseed oil does not increase docosahexaenoic acid in their milk". American Journal of Clinical Nutrition. 77 (1): 226–233. doi: 10.1093/ajcn/77.1.226 . PMID   12499346 . Retrieved 21 November 2022.

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