Essential fatty acid

Essential fatty acids or EFAs) are needed for healthy functioning but cannot be made from other molecules in the body (many other nutrients can be built out of other molecules). However, they can usually be supplied through the diet.

Structure
Essential fatty acids have double bonds between adjacent carbon atoms :C=C: which are destroyed during hydrogenation, so hydrogenated oils lack important EFAs. Animal fats naturally are low in such bonds and also lack important EFAs. Fats with fewer of these specific bonds tend to be more solid at room temperature (they stack more closely because the double bonds make the structure more irregular, and less or no double bonds make the structure more regular so the molecules fit more closely together).

Purpose
Essential fatty acids are important for skin integrity, blood clotting, maintaining cell membranes, the brain and nerves, and immune function, and healing wounds, as well as providing materials to build other needed nutrients.

Learn more

 * Essential Fatty-Acids-Linus Pauling Institute Micronutrient Information Center
 * Vanderbilt student project on essential fatty acids
 * Wiley animation (note it hasn't yet loaded for me but the publishers sometimes offer their material online)