Oily fish, also known asblue fish orfatty fish,[1] arefish species withoil (fats) insoft tissues and in thecoelomic cavity around thegut. Theirfillets may contain up to 30% oil, although this figure varies both within and between species. Examples of oily fish include smallforage fish such assardines,herring andanchovies, and other largerpelagic fish such assalmon,trout,tuna,swordfish andmackerel.[2]
Oily fish can be contrasted withwhitefish, which contain oil only in theliver and in much less overall quantity than oily fish.[1] Examples of whitefish arecod,haddock andflatfish. White fish are usuallydemersal fish which live on or near the seafloor, whereas oily fish are pelagic, living in thewater column goes from the bottom.
Oilyfish meat is a good source of importantfat-solublevitamins such asVitamin A andD, and is rich inomega-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 concerningheart diseases such as stroke and ischemic heart disease;[3] however, oily fish are known to carry higher levels ofcontaminants (such asmercury ordioxin orPOPs) than whitefish.[citation needed] Among other benefits, studies suggest that the omega-3 fatty acids in oily fish may help improve inflammatory conditions such asarthritis.[4]
A 1997 study published inAnnals of Neurology followed 5,386 elderly participants in Rotterdam. It found that fish consumption decreased the risk ofdementia.[5] 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.[6]
French research published in 2002 in theBritish Medical Journal (BMJ) followed 1,674 elderly residents of southernFrance 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.[6] There was a possibleconfounding factor in that individuals with higher education have both a lower risk of dementia and higher consumption of fish.[7]
Consuming 200–400 g of oily fish twice per week may also help prevent sudden death due tomyocardial infarction by preventingcardiac arrhythmia.[8] Theeicosapentaenoic acid found in fish oils appears to dramatically reduce inflammation through conversion within the body toresolvins, with beneficial effects for thecardiovascular system andarthritis.[9]
.jpg)
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 UKFood 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 ingestingpolychlorinated 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.[10]
TheUnited States Environmental Protection Agency's (EPA) Exposure Reference Dose (RfI) formethylmercury (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".[11] 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 ofwhite fish.
The EPA and 2007U.S. Department of Agriculture guidelines sets a limit only on consumption of fatty fish with greater than one part per million of methylmercury, specificallytilefish,king mackerel,shark andswordfish.[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]
Concerns aboutcontamination,diet orsupply have led to investigation of plant sources of omega-3 fatty acids, notablyflax,hempseed andperilla oils.Lactating women who supplemented their diet with flaxseed oil showed increases in blood andbreastmilk concentration ofalpha-linolenic acid andeicosapentaenoic acid but no changes to concentrations ofdocosahexaenoic acid.[12]
| Aboutfish |  | ||||
|---|---|---|---|---|---|
| Anatomy and physiology | |||||
| Sensory systems | |||||
| Reproduction | |||||
| Locomotion | |||||
| Other behaviour | |||||
| Byhabitat | |||||
| Other types | |||||
| Commerce |
| ||||
| Major groups | |||||
| Lists | |||||
