Omega-3

[[File:Alpha-Linolenic acid Structural Formulae V.1.svg|thumb|right|165px|α-Linolenic acid, an omega-3 fatty acid]]
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'''Omega-3''' is a family of organic molecules present in many [[food]]s, technically defined as "polyunsaturated fatty acids (PUFAs) with a double bond (C=C) at the third [[carbon]] atom from the end of the carbon chain".<ref name=wp>{{wpa|Omega-3 fatty acid}}</ref> They are found in both [[plants]] and [[animals]], with dietary sources including seeds, nuts, leafy vegetables, [[fish]], flax-fed hen's eggs, and some meats. They are most closely associated with '''fish oil''', to the extent that many reports about the health benefits of fish oil actually refer to omega-3 from other sources.

A wide variety of beneficial effects are claimed for them, some well-demonstrated, but most unsubstantiated. There is evidence that eating oily fish, which is rich in some types of omega-3, can prevent heart disease and other cardiovascular problems, but despite omega-3 supplements being an industry worth $25 billion in 2011, there is no evidence of a health benefit to justify taking supplements, and nor is there strong evidence as to the benefit of plant sources.<ref name=amn/><ref name=bda/><ref name ="Cochrane2018"/> Additionally, there is an environmental concern related to overfishing sources (including menhaden) used to manufacture fish oil.<ref>The Original Skeptical Raptor. (August 17, 2008). [http://www.skepticalraptor.com/skepticalraptorblog.php/benefits-of-omega-3-fish-oil-somethings-fishy/ Benefits of omega 3 fish oil – something’s fishy] ''Skeptical Raptor''. Retrieved January 26, 2017.</ref><ref>Conniff, R. (December 7, 2012). [http://conservationmagazine.org/2012/12/the-oiliest-catch/ The Oiliest Catch]. ''Conservation''. Retrieved January 26, 2017.</ref>

There are multiple forms of Omega-3. ALA (alpha-linolenic acid) cannot be synthesised in the human body, and is mainly found in vegetables, seeds, and nuts. EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are longer-chain molecules which can be made in the body from ALA, although the process is slow, and your best bet is to eat them as well, and they can be found in foods such as oily fish.<ref name=bda>[https://www.bda.uk.com/foodfacts/omega3.pdf Omega-3 Food Fact Sheet], British Dietetic Association</ref>

Omega-6 fatty acids have a double bond on the 6<sup>th</sup> carbon atom from the end. They are far more prevalent in western diets than omega-3, chiefly in refined vegetable oils used for frying and other cooking, and there is some (inconclusive) evidence that some omega-6 has negative health effects, with a general belief that people should reduce omega-6 and increase omega-3.<ref>{{wpa|Omega-6 fatty acid}}</ref> (If for some reason your body is deficient in omega-6 fatty acids, it can synthesize the amount it needs from omega-3 fatty acids, in the same way it can synthesize EPA/DHA from ALA.)

==Sources==
[[File:Atlantic mackerel (Scomber scombrus).jpg|thumb|right|165px|Atlantic mackerel (''Scomber scombrus''), full of oily goodness]]
;'''ALA:'''
* Vegetable oil<ref name=bda/>
* Rapeseed and linseed (flaxseed);<ref name=bda/> however, these are hard to digest, so it is recommended you crush them<ref name=dofc/>
* Nuts, such as walnuts, pecans, and hazelnuts<ref name=bda/>
* Green leafy vegetables<ref name=bda/> including spinach, kale, Brussels sprouts, and watercress<ref name=webmd/>

;'''DHA/EPA:'''
* Oily fish is a good source, white fish less so. Fish high in omega-3 include mackerel, herring, sprats, pilchards (sardines), etc.; trout and salmon; swordfish (though beware of the high [[mercury]] content); and fresh crab;<ref name=bda/> the ratios of ALA and DHA/EPA vary considerably between fishes;<ref name=dofc/> see below for detailed health recommendations

One study showed that ALA and DHA were present at a high level in the meat of [[goat]]s fed a diet rich in oil palm frond.<ref>[https://www.hindawi.com/journals/bmri/2014/749341/ Omega-3 fatty acid enriched chevon (goat meat) lowers plasma cholesterol levels and alters gene expressions in rats]. Ebrahimi M, Rajion MA, Meng GY, Soleimani Farjam A. ''Biomed. Res. Int.'' 2014;2014:749341. doi: 10.1155/2014/749341. Epub 2014 Feb 25.</ref>

They can also be consumed as a supplement, for instance in fish oil capsules or [[vegetarian]] products obtained from algae, although the evidence is unclear on whether you should.<ref name=bda/><ref name=amn>[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4153275/ Omega-3 Supplements and Cardiovascular Diseases], Azin Mohebi-Nejad1 and Behnood Bikdeli, ''Tanaffos''. 2014; 13(1): 6–14.</ref> A 2018 Cochrane meta-analysis of 79 research papers, however, has pointed to virtually no benefits to reducing heart disease, stroke, and death, or at least not enough benefits as promoted.<ref name ="Cochrane2018">Abdelhamid AS, Brown TJ, Brainard JS, Biswas P, Thorpe GC, Moore HJ, Deane KHO, AlAbdulghafoor FK, Summerbell CD, Worthington HV, Song F, Hooper L. Omega 3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews 2018, Issue 7. Art. No.: CD003177. DOI: [http://cochranelibrary-wiley.com/doi/10.1002/14651858.CD003177.pub3/full 10.1002/14651858.CD003177.pub3].</ref> Some foods, including grain products, dairy, [[soy]] milk, and fruit juice, may be enriched with omega-3, either ALA, DHA, EPA, or some combination.<ref name=dofc/>

==Health claims==
Omega-3 has an anti-inflammatory effect, which may be beneficial in combatting cardiovascular disease, [[cancer]], and disorders of the immune system. In contrast, some omega-6 fatty acids increase inflammation, and there is some evidence that together they may lessen the effects of either or both.<ref>[http://health.howstuffworks.com/wellness/food-nutrition/healthy-eating/5-foods-high-in-omega-3.htm Top 10 Foods High in Omega-3], How Stuff Works</ref>

Omega-3 and specifically types in fish oil are often promoted through their association with the Inuit (because, natural Rousseauian [[Appeal to nature|primitives living in harmony with nature]]) or with another, nearly-as-mystical group, the [[Iceland]]ers.<ref>''The Omega-3 Miracle: The Icelandic Longevity Secret That Offers Super Protection Against Heart Disease, Cancer, Diabetes, Arthritis, Premature Aging, and Deadly Inflammation'' by Garry Gordon's (2004). Freedom Publishing</ref> While the Inuit were central to the initial promotion of fish oil in the 1970s, more recent research has shown they have a [[genetic]] [[adaptation]] which allows them to metabolise omega-3 differently to other people, suggesting that while they may benefit dwellers in the [[Arctic]] with limited diets and the relevant gene, the benefits may not extend beyond that.<ref>[http://www.nytimes.com/2015/09/22/science/inuit-study-adds-twist-to-omega-3-fatty-acids-health-story.html Inuit Study Adds Twist to Omega-3 Fatty Acids’ Health Story], Carl Zimmer, ''New York Times'', 22 Sep 2015</ref>

===Heart disease===
Many organisations, including the American Heart Association, recommend oily fish rich in omega-3 (specifically DHA and EPA) to prevent heart disease. They reduce inflammation, which is likely to have beneficial effects, and may slightly lower blood pressure, reduce clotting, reduce irregular heartbeats, and reduce stroke risk. There is less evidence of health benefits from plant-based sources of omega-3<ref name=mayo>[http://www.mayoclinic.org/diseases-conditions/heart-disease/in-depth/omega-3/art-20045614 Omega-3], Mayo Clinic</ref> and virtually no evidence from fish oil supplements.<ref name ="Cochrane2018"/>

At one point, it was thought that omega-6 fatty acids contributed to heart disease, but this is no longer the case.<ref>[http://www.mayoclinic.org/diseases-conditions/heart-disease/expert-answers/omega-6/faq-20058172 What are omega-6 fatty acids? Can eating omega-6 fatty acids cause heart disease?], Mayo Clinic</ref>

===Brain aging===
Many people believe omega-3 is good for the brain. There are a variety of claims about how omega-3 can combat "brain shrinkage" and affect behaviour and mood.<ref>[http://www.lifeextension.com/Magazine/2014/6/Maximizing-Omega-3-Health-Benefits/Page-01 Maximizing Omega-3 Health Benefits], ''Life Extension Magazine'', 2014</ref> A recent study, carried out in the elderly over 5 years, found no evidence that omega-3 improves the memory or cognitive function.<ref>[http://time.com/4008936/omega-3-brain-benefits-memory/], ''Time'', Aug. 25, 2015</ref><ref>[https://www.nih.gov/news-events/news-releases/nih-study-shows-no-benefit-omega-3-or-other-nutritional-supplements-cognitive-decline NIH study shows no benefit of omega-3 or other nutritional supplements for cognitive decline], NIH</ref>

===Child behaviour===
Some studies have purported to show behavioural benefits in [[children]] given omega-3 supplements.<ref name=atkins>[https://www.theguardian.com/lifeandstyle/2006/oct/12/healthandwellbeing.health1 Catch of the Day], Lucy Atkins, ''The Guardian'', 2006</ref> In the [[UK]], this became a popular idea advanced in [[tabloid]] newspapers, online parenting forums, and school-gate gossip. The ''[[Daily Mail]]'' reported confidently on the wonders of fatty acids from fish-oil (while cautioning people to avoid inferior codliver oil capsules), saying, "For any parents wondering if their children have a deficiency of fatty acids, tell-tale signs are dry and lacklustre skin and hair, dry bumpy skin at the top of the arms and weak, brittle nails."<ref>[http://www.dailymail.co.uk/health/article-206813/Fish-oil-helps-hyperactive-kids.html Fish oil helps hyperactive kids], ''The Daily Mail''</ref> Fish oil products were widely promoted in British education circles, including by the manufacturers of Eye Q fish oil capsules, whose beguiling name practically promised to make your children smarter, and which donated a million pounds worth of capsules to a study by Durham education authority in the mid 2000s.<ref name=atkins/> The Durham study was widely attacked for its failure to use a [[control group]] or any [[Double blind|blinding]], and the failure to specify outcomes to be tested, with [[Ben Goldacre]] calling it "possibly the greatest example of scientific incompetence documented from a local authority".<ref>[https://www.theguardian.com/commentisfree/2008/sep/27/medicalresearch Fish oil exam results fail all the tests], Ben Goldacre, Bad Science, ''The Guardian'', 27 Sep 2008</ref>

This reached fever pitch in 2012 when a study was widely reported in the UK claiming extraordinary benefits in behaviour and reading ability when DHA (from algae rather than fish oil) was given to children, with a control group given a placebo. However, NHS Choices called advice to increase fish oil consumption "highly premature", noting that the study found no overall improvement in children's reading, although there was an improvement in a small subgroup. There was also no improvement in behaviour as rated by teachers, but a small improvement as rated by parents.<ref>[http://www.nhs.uk/news/2012/09September/Pages/Fish-oil-can-make-children-less-naughty.aspx], NHS</ref>{{efn|We're not sure where to begin on the psychology and lack of [[bias]] in parental assessments of their own children's performance.}} It is uncertain if blinding could have been broken by parents smelling or otherwise examining the capsules. Another study was criticised by Ben Goldacre as involving differences in [[brain]] imaging with kids given omega-3 compared with a control, rather than any measurable effects in health or behaviour.<ref>[http://www.badscience.net/2010/06/the-return-of-a-2bn-fishy-friend/ Fish oil in the Observer: the return of a $2bn friend], Ben Goldacre, ''Bad Science'', June 2010</ref> The Royal College of Psychiatrists was critical, saying: "Behavioural problems in children are multifactorial. To rely on diet alone as a strategy for managing difficult behaviour would be a mistake. The evidence base just isn't there for fish oils. Omega-3 is not a [[miracle cure]]. There is no miracle cure."<ref name=atkins/>

===Autism===
{{main|Autism}}
There have been claims in tabloids and other alternative health sources that consuming omega-3 in a fish-rich diet can produce "significant improvements" in the health and behaviour of autistic children.<ref>[http://www.dailymail.co.uk/health/article-74554/How-fishy-diet-help-autistic-children.html How a fishy diet can help autistic children], ''Daily Mail''</ref> However, a 6-month trial in Canada found no changes in behavior.<ref>[https://www.autismspeaks.org/science/science-news/autism-study-fails-show-benefit-omega-3-fatty-acids Autism Study Fails to Show Benefit of Omega-3 Fatty Acids], Autism Speaks, April 10, 2015</ref> It is worthwhile to note that the aforementioned 6-month-trial was reported in [[Autism Speaks]], a controversial organization that [[Autism|actual autistic people]] generally oppose on the basis of being composed of [[Ableism|ableist]] [[asshole]]s.

==Health recommendations==
The British Dietetic Association recommends two portions of fish per week, one being oily, as fish also contains many other nutrients, although they say there's no specific dose recommendation for omega-3 and they do not recommend supplements for healthy adults or children.<ref name=bda/> They also warn that there are risks to pregnant women or women who may be pregnant of consuming large amounts of these fish, especially larger fish like swordfish, shark, and marlin, which may be contaminated with heavy metals or dangerous molecules such as [[PCB]]s, and recommend no more than 2 portions per week for women of childbearing age and 4 portions for other adults.<ref name=bda/> Some fish, such as catfish and tilapia, contains unhealthy fatty acids and aren't so good for you.<ref name=mayo/>

Dietitians of Canada (the Canadian professional body) produces specific recommendations for omega-3 consumption in those aged 19 and over: 1.6 g/day for men; 1.4 g/day for pregnant women; 1.3 g/day for breastfeeding women; 1.1 g/day for other women.<ref name=dofc>[http://www.dietitians.ca/Your-Health/Nutrition-A-Z/Fat/Food-Sources-of-Omega-3-Fats.aspx Food Sources of Omega-3 Fats], Dietitians of Canada</ref> Web MD claims that levels suggested by different sources range from 0.5 to 1 g per day.<ref name=webmd>[http://www.webmd.com/diet/guide/your-omega-3-family-shopping-list Your Omega-3 Family Shopping List], WebMD</ref> However, all these sources recommend that omega-3 is obtained from food, rather than supplements.

==See also==
* [[Oil]]
* [[Superfood]]

==References==
{{Reflist|2|80%}}

==Notes==
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[[Category:Chemicals]]
[[Category:Food woo]]

Categories: Chemicals, Food woo