Synergy between SDA and GLA
As indicated above, both SDA (through EPA) and GLA (through dihomo-GLA) produce anti-inflammatory eicosanoids. Question is, do these components show synergistic effects in the body? Considering the n-6 pathway, dihomo-GLA can potentially be converted to Arachidonic acid (AA). AA, in turn, can deliver inflammatory eicosanoids. Though it is clear from many studies that GLA is safe to consume and shows many benefits, some ARA will be formed and thus be incorporated in cell membranes.
Surprisingly, EPA prevents the formation of AA from dihomo-GLA in humans, creating a full anti-inflammatory set of pre-cursors when consuming Echium oil. Though this theoretically already makes sense, it has also been shown in research done under (physiological) stress and injury. Combinations of GLA and EPA outperformed the individual fatty acids looking at different study outcomes. The combination of GLA and EPA is already used in clinical food when treating lung diseases with inflammatory backgrounds.