Fish oil and krill oil are a source of omega-3 fatty acids, these more specifically being eicospentaenoic acid (EPA) and docosahexaenoic acid (DHA). The best dietary source of omega-3 is oily fish such as sardines, herrings, salmon or mackerel. Also, some foods such as eggs, bread or margarine may be fortified with omega-3 fatty acids EPA and DHA.
Alpha-linolenic acid (ALA) is the parent compound of all of the omega-3 fatty acids. ALA is found in green vegetables, canola oil, and soybeans. The body is able to covert ALA into EPA and DHA, however only a small percentage (<10%) is converted, making this an inefficient source of omega-3 fatty acids in the body. Consuming oily fish regularly in the diet, or alternatively taking fish oil supplements, is important as the body cannot produce omega-3 fatty acids, nor can it convert omega-6 fatty acids, which are plentiful in the Western diet, into omega-3 fatty acids.