Adam Nally, D.O.
By the way, the eicosapentanoic & docosahexanoic acids that are the active fatty acids in fish & cod liver oils (EPA & DHA) are not true base omega-3 oils, they are DERIVATIVES, in other words made from Omega-3, but the body has a naturally very low requirement for EPA & DHA, and the body can make them from the base or parent omega-3 flax oil but only makes them in the amounts required and only when needed. The natural & normal conversion rate is ONLY 2 to 4 or 5 percent of the base omega-3 flax oil, but the low conversion rate commonly believed to be "inefficient" or "impaired" due to "defective" desaturase enzyme activity but that is wrong, there is just a naturally low presence of tissues in the body requiring EPA & DHA and therefore low physiological demand.
Also by the way, the omega-3 oils in fatty fish actually come from seaweed & algae, an ocean plant that grows by photosynthesis just like land plants, that is eaten by krill which are then eaten by small fish which are eaten by bigger fish & on up the food chain. From the Wiki article Omega-3 Fatty Acid: "Omega 3 fatty acids are formed in the chloroplasts of green leaves and algae. While seaweeds and algae are the source of omega 3 fatty acids present in fish, grass is the source of omega 3 fatty acids present in grass fed meats." And from Wikipedia re Fish Oil: "Fish do not actually produce omega-3 fatty acids, but instead accumulate them by consuming either microalgae or prey fish that have accumulated omega-3 fatty acids..."
And a final by the way, humans do NOT require more than 1 gram, 1/5th of a teaspoon, of Omega-3's per day since more than 4 or 5 grams of ANY polyunsaturated oil destabilizes our cell membranes and makes them too thin, fluid & flexible, weak & leaky. Humans need more of the firmer saturated fats for optimum cell membrane conformation since we make our own body heat and at 98.6 are just 1.4 degrees from 100F. See the Wiki article re Homeoviscous Adaptation, deep sea arctic fish can change the oil in their cell membranes to incorporate more omega-3 so they don't freeze up like a car in winter, then replace the omega-3's with saturated fats when they move to warmer waters around the equator. ONLY deep sea cold water fish require high levels of omega-3's, humans don't, humans actually require 2 to 3 grams per day of natural, unadulterated, unprocessed organic, cold extracted CIS omega-6 linoleic acid based on human tissue requirements. Human skin is all omega-6, there's NO omega-3's in skin and O-3 will not protect from melanoma, and the arterial system is also all omega-6 tissue.
For more see the Wikipedia pages about any of the terms above, start with Fatty Acid, then Essential Fatty Acids, then Eicosanoids, Omega-6, Omega-3, etc.