Oily fish have
oilFish oil is oil derived from the tissues of oily fish. Fish oils contain the omega-3 fatty acids eicosapentaenoic acid , and docosahexaenoic acid , precursors of certain eicosanoids that are known to reduce inflammation throughout the body, and are thought to have many health benefits.Fish do not...
in their tissues and in the belly cavity around the
gutIn zoology, the gut, also known as the alimentary canal or alimentary tract, is a tube by which bilaterian animals transfer food to the digestion organs. In large bilaterians the gut generally also has an exit, the anus, by which the animal disposes of solid wastes...
. Their
filletA fillet is a cut or slice of boneless meat or fish.- Meat :In the case of beef, in the USA, the term most often refers to beef tenderloin, especially filet mignon.- Chicken :...
s contain up to 30 percent oil, although this figure varies both within and between species. Examples include small
forage fishForage fish, also called prey fish or bait fish, are small fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical ocean forage fish feed near the base of the food chain on plankton, often by filter feeding...
, such as sardines,
herringHerring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...
and anchovies, and other larger
pelagic fishPelagic fish live near the surface or in the water column of coastal, ocean and lake waters, but not on the bottom of the sea or the lake. They can be contrasted with demersal fish, which do live on or near the bottom, and reef fish which are associated with coral reefs.The marine pelagic...
, such as
salmonSalmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...
,
troutTrout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...
,
hilsaIlish , also spelled Elish, is the most popular fish to Bengalis. Its the national fish of Bangladesh and extremely popular in parts of India such as West Bengal, Orissa, Tripura, Assam as well. Ilish also can be found at India's Assamese-, Bengali- Oriya-speaking regions and in Telugu-speaking...
and
mackerelMackerel is a common name applied to a number of different species of fish, mostly, but not exclusively, from the family Scombridae. They may be found in all tropical and temperate seas. Most live offshore in the oceanic environment but a few, like the Spanish mackerel , enter bays and can be...
.
Oily fish can be contrasted with
whitefishWhitefish or white fish is a fisheries term referring to several species of demersal fish with fins, particularly cod , whiting , and haddock , but also hake , pollock , or others...
, which contain oil only in the
liverThe liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
, and much less overall than oily fish. Examples of whitefish are
codCod is the common name for genus Gadus, belonging to the family Gadidae, and is also used in the common name for various other fishes. Cod is a popular food with a mild flavor, low fat content and a dense, flaky white flesh. Cod livers are processed to make cod liver oil, an important source of...
,
haddockThe haddock , also known as the offshore hake, is a marine fish distributed on both sides of the North Atlantic. Haddock is a popular food fish and is widely fished commercially....
and
flatfishThe flatfish are an order of ray-finned fish, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the head, one or the other migrating through and around the head during development...
. Whitefish are usually demersal fish which live on or near the seafloor, whereas oily fish are
pelagicPelagic fish live near the surface or in the water column of coastal, ocean and lake waters, but not on the bottom of the sea or the lake. They can be contrasted with demersal fish, which do live on or near the bottom, and reef fish which are associated with coral reefs.The marine pelagic...
, living in the water column away from the bottom.
Oily fish are a good source of
VitaminA vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...
s
AVitamin A is a vitamin that is needed by the retina of the eye in the form of a specific metabolite, the light-absorbing molecule retinal, that is necessary for both low-light and color vision...
and
DVitamin D is a group of fat-soluble secosteroids. In humans, vitamin D is unique both because it functions as a prohormone and because the body can synthesize it when sun exposure is adequate ....
, and are rich in Omega 3 fatty acids (whitefish contain the same nutrients but at a much lower level). For this reason the consumption of oily fish rather than whitefish can be more beneficial to humans, particularly concerning cardiovascular diseases, but oily fish are known to carry higher levels of contaminants (such as
mercuryMercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
or
dioxinPolychlorinated dibenzodioxins , or simply dioxins, are a group of organic polyhalogenated compounds that are significant environmental pollutants. They are commonly but inaccurately referred to as dioxins for simplicity, because every PCDD molecule contains a dioxin skeletal structure as the...
) than whitefish. Amongst other benefits, studies suggest that the Omega 3 fatty acids in oily fish may help sufferers of
depressionMajor depressive disorder is a mental disorder characterized by an all-encompassing low mood accompanied by low self-esteem, and by loss of interest or pleasure in normally enjoyable activities...
and improve inflammatory conditions such as
arthritisArthritis is a form of joint disorder that involves inflammation of one or more joints....
.
Dementia
French research published in 2002 in the
British Medical JournalBMJ is a partially open-access peer-reviewed medical journal. Originally called the British Medical Journal, the title was officially shortened to BMJ in 1988. The journal is published by the BMJ Group, a wholly owned subsidiary of the British Medical Association...
followed 1,674 elderly residents of southern
FranceThe French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
for seven years, studying their consumption of meat versus seafood and the presence of
dementiaDementia is a serious loss of cognitive ability in a previously unimpaired person, beyond what might be expected from normal aging...
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. However the study was unclear as to whether fish consumption protected against dementia, or if dementia prevented the participants from wanting more fish. There was also a possible confounding factor in that individuals with higher education have both a lower risk of dementia and higher consumption of fish.
Ocular health
A 2009 study in the
British Journal of OphthalmologyThe British Journal of Ophthalmology is a peer-reviewed medical journal covering clinical investigations, clinical observations, and clinically relevant laboratory investigations related to ophthalmology...
concluded that the Omega-3 fatty acids in oily fish were beneficial both in preventing the onset and slowing the progression of age-related macular degeneration in the elderly. The researchers suggested that people at risk should eat two portions of oily fish per week.
Cardiovascular health
Consuming oily fish twice per week may also help prevent sudden death due to
myocardial infarctionMyocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
by preventing cardiac arrhythmia. The
eicosapentaenoic acidEicosapentaenoic acid is an omega-3 fatty acid. In physiological literature, it is given the name 20:5. It also has the trivial name timnodonic acid...
found in fish oils appears to dramatically reduce inflammation through conversion within the body to
resolvinsResolvins are compounds that are made by the human body from the omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid . They are produced by the COX-2 pathway especially in the presence of aspirin...
, with beneficial effects for the cardiovascular system and
arthritisArthritis is a form of joint disorder that involves inflammation of one or more joints....
.
Recommended consumption
In 1994, the
UKThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
Committee on Medical Aspects of Food and Nutrition Policy (COMA) 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 AgencyThe 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 throughout the United Kingdom and is led by a board appointed to act in the public interest...
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 methylmercury (MeHg).
The
United States Environmental Protection AgencyThe U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
's (EPA) Exposure Reference Dose (RfI) for 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 fishWhitefish or white fish is a fisheries term referring to several species of demersal fish with fins, particularly cod , whiting , and haddock , but also hake , pollock , or others...
.
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
tilefishTilefishes, also known as blanquillo, are mostly small perciform marine fish comprising the family Malacanthidae.They are usually found in sandy areas, especially near coral reefs....
,
king mackerelThe king mackerel is a migratory species of mackerel of the western Atlantic Ocean and Gulf of Mexico. It is an important species to both the commercial and recreational fishing industries.-Description:...
,
sharkSharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
and
swordfishSwordfish , also known as broadbill in some countries, are large, highly migratory, predatory fish characterized by a long, flat bill. They are a popular sport fish of the billfish category, though elusive. Swordfish are elongated, round-bodied, and lose all teeth and scales by adulthood...
. 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 fewer per week. Albacore tuna should be limited to 6 oz or less per week.
Omega-3 content
Concerns about contamination,
dietVegetarianism encompasses the practice of following plant-based diets , with or without the inclusion of dairy products or eggs, and with the exclusion of meat...
or
supplyOverfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....
have led to investigation of plant sources of Omega-3 fatty acids, notably flax, hempseed and
perilla oilPerilla oil is obtained from the seeds of herbs of the genus Perilla, usually from the species Perilla frutescens. The seeds contain 35 to 45 percent oil which is obtained by pressing. Perilla oil is used along with synthetic resins in the production of varnishes...
.
LactatingLactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process occurs in all female mammals, however it predates mammals. In humans the process of feeding milk is called breastfeeding or nursing...
women who supplemented their diet with flaxseed oil showed increases in blood and breastmilk concentration of
alpha-linolenic acidα-Linolenic acid is an organic compound found in many common vegetable oils. In terms of its structure, it is named all-cis-9,12,15-octadecatrienoic acid. In physiological literature, it is given the name 18:3 ....
and
eicosapentaenoic acidEicosapentaenoic acid is an omega-3 fatty acid. In physiological literature, it is given the name 20:5. It also has the trivial name timnodonic acid...
but no changes to concentrations of
docosahexaenoic acidDocosahexaenoic acid is an omega-3 fatty acid that is a primary structural component of the human brain and retina. In chemical structure, DHA is a carboxylic acid with a 22-carbon chain and six cis double bonds; the first double bond is located at the third carbon from the omega end...
.
Further reading
- Clover, Charles. 2004. The End of the Line: How overfishing is changing the world and what we eat. Ebury Press, London. ISBN 0-09-189780-7
External links