Our body requires a regular source of essential fatty acids, these are the ones that we cannot manufacture ourselves. We require two types of omega oil, n3 and n6, with omega 3 hogging the limelight because most of us consume plenty of n6 fatty acids but are usually deficient in n3 fatty acids. The term omega 3 is often used interchangeably with fish oils although there are other fish-free sources of omega 3 fatty acids. The research suggests that fish oils are the superior source although I do have concerns regarding the toxic accumulation of heavy metals in some fish oils. I also believe that as humans spread across the planet tens of thousands of years ago, a growing number of the population would have inhabited areas that are too far from a fresh source of fish, and so would have intuitively found other plant based sources of omega 3 and/or developed ways of extracting the oils from plant based sources. This most likely would have been intuitive, rather than planned.
With this in mind the main sources of omega 3 are a very pure fish oil, which is derived from wild Alaskan or Nordic fish and is cold pressed to retain the goodness and does not undergo any super heating processes such as pasteurisation. The alternative is a plant based source from flax/linseed, hemp and/or evening primrose oil with the best veggie nutrients coming from a combination of two plant sources. Furthermore, in my experience the liquid sources of all varieties are less likely to have been preserved by pasteurisation and it is clearly obvious if the oil is rancid especially fish; something that you are unable to tell from a capsule, until it repeats on you an hour later. My preference it to mix it up and vary the liquid oil that I consume. I add a spoonful to our morning smoothie, you wouldn’t even know it was there.