searchspell:fatty acidscorrected for essential fatty acids
Essential fatty acids, or EFAs, are fatty acids that are required in the human diet. This means they cannot be synthesized by the body from other fatty acids and must be obtained from food. There are two closely related families of EFAs: ω-3 (or omega-3 or n-3) and ω-6 (omega 6, n-6.) They were originally designated as Vitamin F when they were discovered as essential nutrients in 1923. Around 1930, it was realized that they are better classified with the fats than with the vitamins. They were given the label "essential" when researchers found that removal of fatty acids from the diet harmed the normal growth of young children and animals.
FunctionsIn the body, essential fatty acids serve multiple funtions. In each of these, the balance between dietary ω-3 and ω-6 strongly affects function
NomenclatureFatty acids are straight chain (saturated or unsaturated) hydrocarbons ending with a carboxylic acid (COOH) group. Standard nomenclature designates the COOH as the alpha end and names acids by the distance to the first double bond. But biological processes extend acids by adding two carbons at the COOH end. The distance from the ω end (the -CH3 end) does not change. EFAs are therfore named by the position of the first double bond from the ω end. The third bond is a C=C double bond in ω-3 fatty acids. The number of carbons and the number of double bonds is also listed. ω-3 18:4 (stearidonic acid) indicates an 18-carbon chain with 4 double bonds, and with the first double bond in the third position from the CH3 end. Double bonds are cis and separated by a single methylene (CH2) group unless otherwise noted. So stearidonic acid is: Chemical structure of stearidonic acidExamplesThe essential fatty acids are:
These two fatty acids cannot be synthesised by humans, as humans lack the desaturase enzymes required for their production. They form the starting point for the creation of longer and more desaturated fatty acids, which are also referred to as long-chain polyunsaturates:
ω-9 fatty acids are not essential in humans, because humans possess all the enzymes required for their synthesis. Food sourcesSome of the food sources of ω-3 and ω-6 fatty acids are fish and shellfish, flaxseed (linseed), soya oil, canola (rapeseed) oil, hemp oil, chia seeds, pumpkin seeds, leafy vegetables, and walnuts. 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. The IUPAC Lipid Handbook (in .pdf format) 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 publishes 'Essential Fats in Food Oils.' This lists 40 common oils, more tightly focused on EFAs and sorted by n-6:3 ratio. Stuchlik and Zak, 'Vegetable Lipids as Components of Functional Food' (in .pdf format) list notable vegetable sources of EFAs as well as commentary and an overview of the biosynthetic pathways involved. Users can interactively search at Nutrition Data 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. See also
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