Flax seeds have to be ground as the hull of the seed cannot be digested. Once ground the ALA in flax rapidly oxidizes, becoming ever more rancid. Rancid fats will cause health problems. After being ground flax needs to be stored in a refrigerator to slow down the process of oxidation.

The plant based ALA omega 3's have a low bioavailability due to the body having to convert them to DHA/EPA and this conversion process having a low efficiency. In addition, the consumption of omega 6 fats competes with that of omega 3 - proper omega 3 supplementation requires managing the intake ratio of Omega 3 and Omega 6 fats so that they are at, or close to, 1:1. Approximately 5-15% of ALA is converted to DHA/EPA and a precentage of that will make it through the enzymic competition with omega 6 fatty acids. So, in essence, 2.5 grams of ALA equates to 250mg of DHA/EPA while a decent sized filet of wild salmon, with the skin, contains about 2 grams of EPA/DHA.

The absorbtion of supplementary omega 3 fats is increased when taken alongside a high fat meal. The theory explaining this stems from omega 3 fats needing other fats in order to be absorbed by the body. It is hypothetized that the fat profile of fish and game is ideal as that is what the body has evolved to utilize. However, substituting with coconut oil, avacado, or nuts is acceptable in my opinion.

A better alternative to flax is chia seeds, but even this is a poor substitute for eating fresh fish that is cooked to preserve the omega 3 fats (baked or steamed at 300F for ~25 minutes), which is necessary as heat destroys omega 3 fats quite readily.

Most fish oil supplements use Ester oils. These have a very poor bioavailability. I recommend using Nordic Naturals as the triglyceride form they use has superior bioavailability.