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Omega fatty acidsEssential fatty acids (EFA) - or omega fatty acids, as they are often referred to - are essential because:
your body cannot make them on its own, and
Both, essential and non-essential fatty acids are building blocks of dietary fats.
Out of all saturated and unsaturated fatty acids, your body cannot make only two kinds: so called Omega-6 (or EFA6) and Omega-3 (EFA3) unsaturated fatty acids. And if they are deficient in the diet, it can cause many symptoms and serious health conditions.
Omega-6 are polyunsaturated fatty acids - where "polyunsaturated" indicates that they have more than one double bond, and '"6" indicating that their first double bond is located at the 6th carbon atom from fatty acid's methyl group end (CH3, carbon atom single-bonded to three hydrogen atoms, also called omega, or ω group). Short-term Omega-6 deficiency can cause skin eruptions, hair loss, liver and kidney degeneration, and suppressed immune-function, among other symptoms; its prolonged absence is fatal.
On the other hand, excessive intake of Omega-6 fatty acids, even those not degraded by processing, can produce oxidative/inflammatory damage by stimulating production of inflammatory leucotrienes, and may promote clot formation, especially if the Omega-3 are deficient.
Omega-3 are also polyunsaturated fatty acids, but with their first double bond at the 3rd carbon atom from their omega group end. Their deficiency could cause growth retardation as well as neural dysfunction on various levels; also, they have anti-inflammatory and anti-clotting properties, and it seem to be playing important part in protection from cardiovascular diseases.
In the absence of dietary EFA intake, the body can partly compensate for their deficiency by inserting double bonds in other fatty acids, primarily those that are monounsaturated, like oleic acid, the most abundant fatty acid in olive oil. This adds to the health benefits of this type of dietary fat, but neglecting dietary intake of EFAs on that basis is not advisable.
There are several main molecular forms of both, EFA6 and EFA3, based on the size of their molecules (i.e. on the length of their carbon chain). According to it, they are classified as short-, medium- and long-chain EFAs, with the longer forms being also more unsaturated.
The shortest EFA6 forms, containing 18 carbon atoms, are Linoleic acid (LA, 18:2ω6, where 2ω6 means that it has two double bonds, with the first located at the 6th carbon atom from the omega group end), and Gamma-linolenic acid (GLA, 18:3ω6). The two main longer-chain molecular forms are Dihomogammalinolenic acid (DGLA, 20:3ω6) and Arachidonic acid (AA, 20:4ω6).
On the other hand, the shortest EFA3 form, also with 18 carbon atoms, is Alpha-linolenic acid (ALA or LNA 18:3ω3), with the main longer forms being medium-chain Eicosapentaenoic acid (EPA, 20:5ω3) and long-chain Docosahexaenoic acid (DHA, 22:6ω3). The abbreviations are commonly in use - you can see why.
These different EFA molecules have their specific functions in the body, primarily at the cellular level. It includes vital role in energy production, transfer of oxygen, cellular membrane function and cell division.
In other words, we need all EFAs. By adding carbon groups and/or inserting double bonds via desaturase enzymes, healthy body can produce longer-chain EFAs from their basic short-chain forms, Linoleic and Alpha-linolenic acid, which are the two basic EFA forms found in plant food sources. The two main EFA forms found in animal food sources (mainly fish and marine animals) are the medium-chain EPA and long-chain DHA. Some meats also have relatively significant Linoleic acid content.
Essential fatty acids DRI (Dietary Reference Intakes, the most recent set of dietary recommendations set by the government) for an average healthy adult is set at 5%-10% of the total caloric intake for Omega-6, and 0.6%-1.2% for Omega-3.
According to Udo Erasmus, probable optimum for the
Omega-6 and Omega-3 fatty acids food sources
Best single food source of the two basic essential fatty acids, with near optimum ratio of Omega-6 (LA) to Omega-3 (ALA) - about 3 to 1 - is hemp oil. However, intake of the Omega-6 in the general population today is significantly higher than what it was in the past, contrary to the intake of the Omega-3 which is now only a fraction of what it was in the 19th century.
This implicates that the Omega-3 deficiency in general population is much more likely, in which case the best dietary source (for 6-12 month period, which is usually needed to correct Omega-3 deficiency) becomes flax oil, with the Omega-6 to Omega-3 ratio nearly reversed: about 1 to 3.
Plant seed oils from evening primrose, borage and black currant have high contents of essential EFAs, but mainly LA and GLA. The latter makes them important for those who - due to either body malfunction, nutritional deficiency or other - can't make GLA (hence neither longer-chain polyunsaturated EFAs) from LA.
Other plant sources of both Omega-3 and Omega-6 are walnut (LA), soybean (mainly LA, some ALA) and canola oil (mainly LA, and some ALA), but only in their natural, un-refined form. Safflower, sunflower, corn, and sesame, as well as most nuts, only contain Omega-6 (LA).
Meat and poultry also contain only Omega-6 EFA (LA), roughly from 2% (beef) to about 20% (poultry) of the total fatty acids. Pork fat contains some 10% LA - not enough to make it a healthful source of dietary fat. Both, cow and goat milk have only traces of EFA, while mare milk has significant Omega-3 content: ALA makes nearly 40% of its total fat.
Free-range eggs also contain EFAs (free-range animals, in general, have significantly higher EFA fat content, including the Omega-3).
Cold water fish - salmon, sardines, mackerel, trout and eel - are good source of Omega-3 fatty acids (specifically, EPA and DHA, considered to be particularly beneficial for cardiovascular health), with comparatively low Omega-6 content.
* Fresh, unprocessed foods (EFAs are easily destroyed by heat/air/light exposure)
For the proper function of essential fatty acids, body needs to have sufficient levels of vitamins A, E, C, B3 and B6, as well as magnesium, zinc and selenium available. Most of these nutrients, or their metabolites, are necessary co-factors for the enzymes (delta desaturase) converting short-chain EFAs - LA and ALA - into longer-chain forms.
With respect to this, it should be emphasized that a nominally
sufficient dietary intake of short-chain EFAs in the form of LA and ALA, usually from hemp or flax oil, doesn't guarantee sufficient body levels of the important longer-chain EFAs, like GLA, EPA and DHA.
If your enzymatic conversion from short to longer-chain EFAs is inefficient - either due to advanced age, genetics, nutritional deficiencies (specifically, vitamin B6, magnesium and zinc, needed for the key conversion enzyme, delta-6-desturaze), extensive oxidative damage at the cellular level, or disease - you need to secure direct intake of the longer-chain EFAs through diet or (likely) supplementation, or your health will suffer.
There is no unsafe (excessive) intake level established for essential fatty acids. However, moderation is, as always, prudent.