Essential fatty acids

Essential fatty acids

Essential fatty acids, or EFAs, are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them.The term “essential fatty acid” refers to fatty acids required for biological processes, and not those that only act as fuel.

Only two EFAs are known for humans: alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid. Other fatty acids that are only “conditionally essential” include gamma-linolenic acid (an omega-6 fatty acid), lauric acid (a saturated fatty acid), and palmitoleic acid (a monounsaturated fatty acid).

When the two EFAs were first discovered in 1923, they were designated “vitamin F”. In 1930, research on rats showed that the two EFAs are better classified with the fats than with the vitamins.

Food sources

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Some of the food sources of ω-3 and ω-6 fatty acids are fish and shellfishflaxseed (linseed)hemp oilsoya oilcanola (rapeseed) oilchia seeds pumpkin seedssunflower seedsleafy vegetables, andwalnuts.

Essential fatty acids play a part in many metabolic processes, and there is evidence to suggest that low levels of essential fatty acids, or the wrong balance of types among the essential fatty acids, may be a factor in a number of illnesses, including osteoporosis.

Plant sources of ω-3 contain neither eicosapentaenoic acid (EPA) nor docosahexaenoic acid (DHA). The human body can (and in case of a purely vegetarian diet often must, unless certain algae or supplements derived from them are consumed) convert α-linolenic acid (ALA) to EPA and subsequently DHA. This however requires more metabolic work, which is thought to be the reason that the absorption of essential fatty acids is much greater from animal rather than plant sources (see Fish and plants as a source of Omega-3 for more).

The IUPAC Lipid Handbook provides a very large and detailed listing of fat contents of animal and vegetable fats, including ω-3 and -6 oils. The National Institutes of Health‘s EFA Education group publishesEssential Fats in Food Oils. This lists 40 common oils, more tightly focused on EFAs and sorted by n-6:3 ratio. Vegetable Lipids as Components of Functional Food lists notable vegetable sources of EFAs as well as commentary and an overview of the biosynthetic pathways involved.[ Users can interactively search at NutritionData.com for the richest food sources of particular EFAs or other nutrients. Careful readers will note that these sources are not in excellent agreement. EFA content of vegetable sources varies with cultivation conditions. Animal sources vary widely, both with the animal’s feed and that the EFA makeup varies markedly with fats from different body parts.

Almost all the polyunsaturated fats in the human diet are EFAs. Essential fatty acids play an important role in the life and death of cardiac cells.

Essential fatty acid deficiency results in a dermatitis similar to that seen in zinc or biotin deficiency.

Treatment for depression

Research suggests that high intakes of fish and omega-3 fatty acids are linked to decreased rates of major depression. Omega-3 fatty acids, such as docosahexaenoic acid (DHA) and eicosapentaenoic acid(EPA) are important for enzymatic pathways required to metabolize long-chain polyunsaturated fatty acids (PUFAs). Low plasma concentrations of DHA predict low concentrations of cerebrospinal fluid 5-hydroxyindoleacetic acid (5-HIAA). It is found that low concentrations of 5-HIAA in the brain is associated with depression and suicide.

There are high concentrations of DHA in synaptic membranes of the brain. This is critical for synaptic transmission and membrane fluidity. The omega-6 fatty acid to omega-3 fatty acid ratio is important to avoid imbalance of membrane fluidity. Membrane fluidity affects function of enzymes such as adenylate cyclase and ion channels such as calciumpotassium, and sodium, which in turn affects receptor numbers and functioning, as well as serotonin neurotransmitter levels. It is evident that western diets are deficient in omega-3 and excessive in omega-6, and balancing of this ratio would confer numerous health benefits.

Clinical research suggests a benefit of omega-3 fatty acids in the treatment of depression during the perinatal period. A meta analysis of trials of EPA supplements for depression in non-pregnant adults concluded that supplments with more than 60% EPA are effective, but those containing primarily DHA, or less than 60% EPA, were not effective.

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