View source for Oily fish

{{Short description|Fish species with oils in their tissues and coelom}}
{{for|the species of snake mackerel|Oilfish}}
{{Use dmy dates|date=September 2014}}
[[File:Bluefin-big.jpg|thumb|The large [[Pelagic fish|open-water]] [[Atlantic bluefin tuna]] is an oily fish.]]
[[File:Anchovy closeup.jpg|thumb|Most small [[forage fish]], like these [[Shoaling and schooling|schooling]] [[Anchovy|anchovies]], are also oily fish.]]

'''Oily fish,''' also known as '''blue fish''' or '''fatty fish''',<ref name="Bluefish, Whitefish-Delfin Ultracongelados">{{cite web |title=Types of fish: Bluefish, Whitefish and Semi-fatty fish |url=https://www.delfinultracongelados.es/en/types-of-fish/#:~:text=Contrary%20to%20popular%20belief%2C%20the,fish%20only%20have%20about%202%25. |website=Delfin Ultracongelados |access-date=30 July 2025 |language=en |date=4 July 2024}}</ref> are [[fish]] species with [[fish oil|oil]] (fats) in [[soft tissue]]s and in the [[coelomic cavity]] around the [[Gut (zoology)|gut]].  Their [[fillet (cut)|fillet]]s 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 [[sardine]]s, [[herring]] and [[anchovy|anchovies]], and other larger [[pelagic fish]] such as [[salmon]], [[trout]], [[tuna]], [[swordfish]] and [[mackerel]].<ref>{{cite web|archive-url=https://web.archive.org/web/20051125085512/http://www.food.gov.uk/news/newsarchive/2004/jun/oilyfishdefinition|archive-date=25 November 2005|website=Food Standards Agency|date=24 June 2004|url=http://www.food.gov.uk/news/newsarchive/2004/jun/oilyfishdefinition|title=What's an oily fish?|access-date=7 September 2005|url-status=dead}}</ref>

Oily fish can be contrasted with [[whitefish (fisheries term)|whitefish]], which contain oil only in the [[liver]] and in much less overall quantity than oily fish.<ref name="Bluefish, Whitefish-Delfin Ultracongelados"/> 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 as food|fish meat]] is a good source of important [[lipophilicity|fat-soluble]] [[vitamin]]s such as [[Vitamin A]] and [[Vitamin D|D]], and is rich in [[omega-3 fatty acid]]s (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 [[cardiovascular disease|heart disease]]s such as stroke and ischemic heart disease;<ref>{{Cite web|url=https://www.newscientist.com/article/mg12416851.600-oily-fish-helps-heart-attack-victims-to-live-longer-.html |title=Oily fish helps heart attack victims to live longer - 07 October 1989 |publisher=New Scientist |date=7 October 1989 |access-date=27 July 2009}}</ref> however, oily fish are known to carry higher levels of [[contaminant]]s (such as [[Mercury in fish|mercury]] or [[dioxins and dioxin-like compounds|dioxin]] or [[persistent organic pollutants|POPs]]) than whitefish.{{citation needed|date=January 2016}} Among other benefits, studies suggest that the omega-3 fatty acids in oily fish may help improve inflammatory conditions such as [[arthritis]].<ref>{{cite journal|title=Fish Oil and Inflammation — A Fresh Look | author= Kremer JM |journal=The Journal of Rheumatology |year=  2017 |volume=  44  |issue=6 |pages=713–716 | doi=10.3899/jrheum.161551 |pmid=28572471 |doi-access=free }}</ref>

== Health benefits ==
[[File:Halibut and salmon fillets.jpg|thumb|Oily fish fillet ([[salmon]] – bottom) contrasted with a [[Whitefish (fisheries term)|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]].<ref name="rotterdam annals">{{Cite journal 
| last1 = Kalmijn | first1 = S. 
| last2 = Launer | first2 = L. J. 
| last3 = Ott | first3 = A. 
| last4 = Witteman | first4 = J. C. M. 
| last5 = Hofman | first5 = A. 
| last6 = Breteler | first6 = M. M. B. 
| doi = 10.1002/ana.410420514 
| title = Dietary fat intake and the risk of incident dementia in the Rotterdam study 
| journal = Annals of Neurology 
| volume = 42 
| issue = 5 
| pages = 776–782 
| year = 1997 
| pmid = 9392577 
| url = https://repub.eur.nl/pub/58975 
| hdl = 1765/58975 
| s2cid = 24435633 
| hdl-access = free 
}}</ref>  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.<ref name="france bmj" />

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.<ref name="france bmj">{{Cite journal 
| last1 = Barberger-Gateau | first1 = P. 
| last2 = Letenneur | first2 = L. 
| last3 = Deschamps | first3 = V. 
| last4 = Pérès | first4 = K. 
| last5 = Dartigues | first5 = J. F. 
| last6 = Renaud | first6 = S. 
| title = Fish, meat, and risk of dementia: Cohort study 
| journal = BMJ (Clinical Research Ed.) 
| volume = 325 
| issue = 7370 
| pages = 932–933 
| year = 2002 
| pmid = 12399342 
| pmc = 130057 | doi=10.1136/bmj.325.7370.932
}}</ref> There was a possible [[confounding]] factor in that individuals with higher education have both a lower risk of dementia and higher consumption of fish.<ref>{{Cite news|last=Wilkinson|first=Emma|url=https://news.bbc.co.uk/1/hi/health/7929071.stm |title=Oily fish dementia boosts queried |website=BBC News |date=9 March 2009|access-date=27 July 2009}}</ref>

=== Cardiovascular health ===

Consuming 200–400&nbsp;g of oily fish twice per week may also help prevent sudden death due to [[myocardial infarction]] by preventing [[cardiac arrhythmia]].<ref>{{cite journal |last1=Leaf |first1=A. |last2=Kang |first2=J. X. |last3=Xiao |first3=Y.-F. |last4=Billman |first4=G. E. |author4-link=George Billman |title=Clinical prevention of sudden cardiac death by n-3 polyunsaturated fatty acids and mechanism of prevention of arrhythmias by n-3 fish oils |journal=Circulation |volume=107 |pages=2646–52 |doi=10.1161/01.CIR.0000069566.78305.33 |pmid=12782616 |year=2003 |issue=21|doi-access=free }}</ref> 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]].<ref>{{cite journal |last = Arita|first = M.|author2 = Bianchini F|author3 = Aliberti J|author4 = Sher A|author5 = Chiang N|author6 = Hong S|author7 = Yang R|author8 = Petasis NA|author9 = Serhan CN|title = Stereochemical assignment, antiinflammatory properties, and receptor for the Omega-3 lipid mediator Resolvin E1|journal = [[J. Exp. Med.|Journal of Experimental Medicine]]|volume = 201|issue = 5|pages = 713–22|pmid = 15753205|year = 2005|doi = 10.1084/jem.20042031|pmc = 2212834}}{{Open access}}</ref>

== Recommended consumption ==
[[File:Thyme and Garlic Grilled Salmon with Mango Salsa, Rosemary Potatoes and Snow Peas (297986190).jpg|thumb|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.<ref>{{cite web|url=http://www.food.gov.uk/multimedia/faq/oilyfishfaq/#.UwIxPDZ_vTo|title=Oily fish advice: your questions answered|date=23 June 2004|access-date=17 February 2014|website=Food Standards Agency|archive-url=https://web.archive.org/web/20131203001459/http://www.food.gov.uk/multimedia/faq/oilyfishfaq/#.UwIx0zZ_vTo|archive-date=3 December 2013|url-status=live}}</ref>

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".<ref>SACN (2004) [https://cot.food.gov.uk/sites/default/files/cot/fishreport200401.pdf ''Advice on fish consumption: benefits and risks''], 20 May 2014, Committee on Toxicity. {{ISBN|011243083X}}.</ref> 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 [[Whitefish (fisheries term)|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|date=January 2016}} 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|date=January 2016}} [[Albacore]] tuna should be limited to six ounces or less per week. {{citation needed|date=January 2016}}

== Omega-3 content ==

Concerns about [[mercury in fish|contamination]], [[Vegetarianism|diet]] or [[Overfishing|supply]] have led to investigation of plant sources of omega-3 fatty acids, notably [[flaxseed oil|flax]], [[hemp oil|hempseed]] and [[perilla oil]]s.  [[Lactation|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]].<ref>{{cite journal |last1=Francois |first1=C.A. |last2=Connor |first2=S. L. |last3=Bolewicz |first3=L. C. |last4=Connor |first4=W. E. |title=Supplementing lactating women with flaxseed oil does not increase docosahexaenoic acid in their milk |journal=American Journal of Clinical Nutrition |url=https://academic.oup.com/ajcn/article/77/1/226/4689657 |access-date=21 November 2022 |volume=77 |issue=1 |pages=226–233 |date=1 January 2003 |pmid=12499346|doi=10.1093/ajcn/77.1.226 |doi-access=free }}</ref>

== See also ==
* [[Fish as food]]
* [[Mercury in fish]]
* [[Whitefish (fisheries term)]]: it is low fat fish.

== References ==
{{Reflist}}

== Further reading ==
* Clover, Charles. 2004. ''The End of the Line: How overfishing is changing the world and what we eat''. [[Ebury Publishing|Ebury Press]], London. {{ISBN|0-09-189780-7}}

== External links ==
*[https://academic.oup.com/ajcn/article/78/3/640S/4690006 Achieving optimal essential fatty acid status in vegetarians: current knowledge and practical implications] (American Journal of Clinical Nutrition)
*[https://web.archive.org/web/20051030031644/http://www.bupa.co.uk/health_information/html/health_news/300604fish.html BUPA article on oily fish]
*[https://www.monbiot.com/2006/06/21/not-enough-fish-in-the-sea/ George Monbiot on the environmental problems of sourcing omega-3 from fish]

{{diversity of fish}}

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[[Category:Oily fish| ]]
[[Category:Biologically based therapies]]
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