Flax is highly over rated IMO. Fish oil has a higher efficacy as it contains EPA/DHA as opposed to the ALNA in flax. The majority of the biological effects of ALNA are generally attributed to conversion to EPA and then DHA via desaturation and elongation. These fatty acids generally have all of the same benefits of ALNA, and then some. In human and animal studies, ALNA successfully raises tissue levels of EPA, but the conversion rate is low (less than 10%). The remaining ALNA is either beta-oxidized for other purposes or partitioned into certain tissues, such as skin. The conversion rate to DHA is very low, so both ALNA and EPA supplementation generally fail to significantly increase tissue DHA content. It is likely that this is because DHA synthesis is regulated largely independently of tissue EPA content.