Is it possible to get all essential fatty acids from eating oily fish?

Phil Hadley, United Kingdom

There are two essential fatty acids: the linoleic acid (omega-6 family) and alpha-linolenic acid (omega-3 family) which cannot be made in the body and must be provided by the diet. They are necessary for growth and development and for maintaining health.

Although these two fatty acids cannot be made in the body they can be converted to longer chain versions (e.g. arachidonic acid, EPA or eicosapentaenoic acid and DHA or docosahexaenoic acid). These longer chain versions provide the building blocks of eicosanoids, which are precursors for hormones (such as prostaglandins). These hormone like substances are important in the formation of cell membranes and are involved in blood clotting, wound healing and inflammation. The conversion of alpha-linolenic acid into EPA and DHA is however limited. For that reason we may also need direct sources of these long chain omega-3 fats in our diet. The richest source of these fatty acids is oily fish. Fish oil contains also omega-6-fats but only in a small amount. Vegetable oils are rich in omega-6 fatty acids, and most Europeans unknowingly get plenty of them in the diet. On the other hand, omega-3 fatty acids are generally lacking in our diets. An increasing consumption of all types of fish is recommended, but oily fishes are richer sources. For those individuals which are not allergic to fish or otherwise can not tolerate fish a fish consumption of minimal one fish meal a week, and not more than three times a week is recommended with respect to a good intake of essential fatty acid provided that on the other day also vegetable oils with enough omega 6 linoleic acid is consumed, which is most likely always the case.

Backgrounder on fat
http://www.foodexperts.org/nutrition-health/backgrounder_fats.php

Omega 3 fatty acids
http://www.eufic.org/pt/food/pag/food38/food381.htm