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Oily fish are
fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...
species with oil (fats) in
soft tissue Soft tissue connective tissue, connects and surrounds or supports internal organs and bones, and includes muscle, tendons, ligaments, Adipose tissue, fat, fibrous tissue, Lymphatic vessel, lymph and blood vessels, fasciae, and synovial membranes.� ...
s and in the coelomic cavity around the gut. Their
fillet Fillet may refer to: *Annulet (architecture), part of a column capital, also called a fillet *Fillet (aircraft), a fairing smoothing the airflow at a joint between two components *Fillet (clothing), a headband *Fillet (heraldry), diminutive of the ...
s may contain up to 30% oil, although this figure varies both within and between species. Examples of oily fish include small
forage fish Forage fish, also called prey fish or bait fish, are small pelagic fish that feed on planktons (i.e. planktivores) and other small aquatic organisms (e.g. krill). They are in turn preyed upon by various predators including larger fish, seabirds ...
such as
sardine Sardine and pilchard are common names for various species of small, oily forage fish in the herring suborder Clupeoidei. The term "sardine" was first used in English during the early 15th century; a somewhat dubious etymology says it com ...
s,
herring Herring are various species of forage fish, belonging to the Order (biology), order Clupeiformes. Herring often move in large Shoaling and schooling, schools around fishing banks and near the coast, found particularly in shallow, temperate wate ...
and
anchovies An anchovy is a small, common forage fish of the family Engraulidae. Most species are found in marine waters, but several will enter brackish water, and some in South America are restricted to fresh water. More than 140 species are placed in 1 ...
, and other larger
pelagic fish Pelagic fish live in the pelagic zone of ocean or lake waters—being neither close to the bottom nor near the shore—in contrast with demersal fish that live on or near the bottom, and reef fish that are associated with coral reefs. ...
such as
salmon Salmon (; : salmon) are any of several list of commercially important fish species, commercially important species of euryhaline ray-finned fish from the genera ''Salmo'' and ''Oncorhynchus'' of the family (biology), family Salmonidae, native ...
,
trout Trout (: trout) is a generic common name for numerous species of carnivorous freshwater ray-finned fishes belonging to the genera '' Oncorhynchus'', ''Salmo'' and ''Salvelinus'', all of which are members of the subfamily Salmoninae in the ...
,
tuna A tuna (: tunas or tuna) is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae ( mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bul ...
,
swordfish The swordfish (''Xiphias gladius''), also known as the broadbill in some countries, are large, highly migratory predatory fish characterized by a long, flat, pointed bill. They are the sole member of the Family (biology), family Xiphiidae. They ...
and
mackerel Mackerel is a common name applied to a number of different species of pelagic fish, mostly from the family Scombridae. They are found in both temperate and tropical seas, mostly living along the coast or offshore in the oceanic environment. ...
. Oily fish can be contrasted with whitefish, which contain oil only in the
liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...
and in much less overall quantity than oily fish. Examples of whitefish are
cod Cod (: cod) is the common name for the demersal fish genus ''Gadus'', belonging to the family (biology), family Gadidae. Cod is also used as part of the common name for a number of other fish species, and one species that belongs to genus ''Gad ...
,
haddock The haddock (''Melanogrammus aeglefinus'') is a saltwater ray-finned fish from the Family (biology), family Gadidae, the true cods. It is the only species in the Monotypy, monotypic genus ''Melanogrammus''. It is found in the North Atlantic Oce ...
and
flatfish A flatfish is a member of the Ray-finned fish, ray-finned demersal fish Order (biology), suborder Pleuronectoidei, also called the Heterosomata. In many species, both eyes lie on one side of the head, one or the other migrating through or around ...
. White fish are usually
demersal fish Demersal fish, also known as groundfish, live and feed on or near the bottom of seas or lakes (the demersal zone).Walrond Carl . "Coastal fish - Fish of the open sea floor"Te Ara - the Encyclopedia of New Zealand. Updated 2 March 2009 They oc ...
which live on or near the seafloor, whereas oily fish are pelagic, living in the
water column The (oceanic) water column is a concept used in oceanography to describe the physical (temperature, salinity, light penetration) and chemical ( pH, dissolved oxygen, nutrient salts) characteristics of seawater at different depths for a defined ...
goes from the bottom. Oily fish meat is a good source of important fat-soluble
vitamin Vitamins are Organic compound, organic molecules (or a set of closely related molecules called vitamer, vitamers) that are essential to an organism in small quantities for proper metabolism, metabolic function. Nutrient#Essential nutrients, ...
s such as
Vitamin A Vitamin A is a fat-soluble vitamin that is an essential nutrient. The term "vitamin A" encompasses a group of chemically related organic compounds that includes retinol, retinyl esters, and several provitamin (precursor) carotenoids, most not ...
and D, and is rich in
omega-3 fatty acid 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 ...
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
heart disease Cardiovascular disease (CVD) is any disease involving the heart or blood vessels. CVDs constitute a class of diseases that includes: coronary artery diseases (e.g. angina pectoris, angina, myocardial infarction, heart attack), heart failure, ...
s such as stroke and ischemic heart disease; however, oily fish are known to carry higher levels of
contaminant Contamination is the presence of a constituent, impurity, or some other undesirable element that renders something unsuitable, unfit or harmful for the physical body, natural environment, wiktionary:Workplace, workplace, etc. Types of contamina ...
s (such as mercury or dioxin or POPs) than whitefish. Among other benefits, studies suggest that the omega-3 fatty acids in oily fish may help improve inflammatory conditions such as
arthritis Arthritis is a general medical term used to describe a disorder that affects joints. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, Joint effusion, swelling, and decreased range of motion of ...
.


Health benefits


Dementia

A 1997 study published in ''
Annals of Neurology ''Annals of Neurology'' is a peer-reviewed medical journal publishing articles of "broad interest in neurology, particularly those with high impact in understanding the mechanisms and treatment of diseases of the human nervous system." The journal ...
'' followed 5,386 elderly participants in Rotterdam. It found that fish consumption decreased the risk of
dementia Dementia is a syndrome associated with many neurodegenerative diseases, characterized by a general decline in cognitive abilities that affects a person's ability to perform activities of daily living, everyday activities. This typically invo ...
. 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. French research published in 2002 in the ''British Medical Journal'' ( BMJ) followed 1,674 elderly residents of southern
France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
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. There was a possible
confounding In causal inference, a confounder is a variable that influences both the dependent variable and independent variable, causing a spurious association. Confounding is a causal concept, and as such, cannot be described in terms of correlatio ...
factor in that individuals with higher education have both a lower risk of dementia and higher consumption of fish.


Cardiovascular health

Consuming 200–400 g of oily fish twice per week may also help prevent sudden death due to
myocardial infarction A myocardial infarction (MI), commonly known as a heart attack, occurs when Ischemia, blood flow decreases or stops in one of the coronary arteries of the heart, causing infarction (tissue death) to the heart muscle. The most common symptom ...
by preventing
cardiac arrhythmia Arrhythmias, also known as cardiac arrhythmias, are irregularities in the heartbeat, including when it is too fast or too slow. Essentially, this is anything but normal sinus rhythm. A resting heart rate that is too fast – above 100 beat ...
. 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 In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. It includes the cardiovascular system, or vascular system, that consists of the heart a ...
and
arthritis Arthritis is a general medical term used to describe a disorder that affects joints. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, Joint effusion, swelling, and decreased range of motion of ...
.


Recommended consumption

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 The Food Standards Agency is a non-ministerial government department of the Government of the United Kingdom. It is responsible for protecting public health in relation to food in England, Wales and Northern Ireland. It is led by a board appoin ...
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 Polychlorinated biphenyls (PCBs) are organochlorine compounds with the formula C12 H10−''x'' Cl''x''; they were once widely used in the manufacture of carbonless copy paper, as heat transfer fluids, and as dielectric and coolant fluids f ...
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. The
United States Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent agency of the United States government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it began operation on De ...
's (EPA) Exposure Reference Dose (RfI) for
methylmercury Methylmercury is an organometallic cation with the formula . It is the simplest organomercury compound. Methylmercury is extremely toxic, and its derivatives are the major source of organic mercury for humans. It is a bioaccumulative environment ...
(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". 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 file:Malacanthus latovittatus.jpg, 250px, Blue blanquillo, ''Malacanthus latovittatus'' Tilefishes are mostly small perciform marine fish comprising the family (biology), family Malacanthidae. They are usually found in sandy areas, especially n ...
, king mackerel,
shark Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...
and
swordfish The swordfish (''Xiphias gladius''), also known as the broadbill in some countries, are large, highly migratory predatory fish characterized by a long, flat, pointed bill. They are the sole member of the Family (biology), family Xiphiidae. They ...
. 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.
Albacore The albacore (''Thunnus alalunga''), known also as the longfin tuna, is a species of tuna of the order Scombriformes. It is found in temperate and tropical waters across the globe in the epipelagic and mesopelagic zones. There are six distinct ...
tuna should be limited to six ounces or less per week.


Omega-3 content

Concerns about
contamination Contamination is the presence of a constituent, impurity, or some other undesirable element that renders something unsuitable, unfit or harmful for the physical body, natural environment, workplace, etc. Types of contamination Within the scien ...
, diet or
supply Supply or supplies may refer to: *The amount of a resource that is available **Supply (economics), the amount of a product which is available to customers **Materiel, the goods and equipment for a military unit to fulfill its mission *Supply, as ...
have led to investigation of plant sources of omega-3 fatty acids, notably
flax Flax, also known as common flax or linseed, is a flowering plant, ''Linum usitatissimum'', in the family Linaceae. It is cultivated as a food and fiber crop in regions of the world with temperate climates. In 2022, France produced 75% of t ...
, hempseed and perilla oils.
Lactating Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process naturally occurs with all sexually mature female mammals, although it may predate mammals. The proces ...
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 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 ...
.


See also

*
Fish as food Many species of fish are caught by humans and consumed as food in virtually all regions around the world. Their meat has been an important dietary source of protein and other nutrients in the human diet. The English language does not have a ...
* Mercury in fish *
Whitefish (fisheries term) Whitefish or white fish is a fisheries term for several species of demersal fish with fins, particularly Atlantic cod (''Gadus morhua''), whiting (fish), whiting (''Merluccius bilinearis''), haddock (''Melanogrammus aeglefinus''), Phycidae, hake ...
: it is low fat fish.


References


Further reading

* Clover, Charles. 2004. ''The End of the Line: How overfishing is changing the world and what we eat''. Ebury Press, London.


External links


Achieving optimal essential fatty acid status in vegetarians: current knowledge and practical implications
(American Journal of Clinical Nutrition)
George Monbiot on the environmental problems of sourcing omega-3 from fish
{{DEFAULTSORT:Oily Fish Biologically based therapies Fishing industry