The Omega-3 Fatty Acid Metabolic Pathway starts with Alpha Lenolenic Acid (ALA).
Good sources of ALA are Flaxseed Oil and Hemp Oil.
ALA is then converted to Steriodonic Acid (SDA).
Black Currant Seed Oil is a good source of SDA.
SDA is then converted to Eicosapentaenoic Acid (EPA).
EPA can then be converted to Docosahexaenoic Acid (DHA).
Fish Oil is a good source of EPA and DHA.
EPA can then be oxidized by the enzyme Cyclooxygenase (Cox) to from Prostaglandin E3.
All these transformations require multiple cofactors and certain healthy conditions.
Thus, Flaxseed oil in some people may not even be converted well to EPA or DHA, if the conditions are not right.
Black Currant Seed Oil would then be more effective since it is closer in proximity to EPA in the pathway and requires fewer cofactors to do the conversion.