A decade ago research indicated a likely causal link between low levels of omega-3 fatty acids (FAs) and a higher prevalence of mood disorders, and also provided quite strong support for omega-3 FAs as both an antidepressant monotherapy and an augmentor of formal antidepressant drugs. Recent research is somewhat less convincing about their antidepressant efficacy but is nevertheless furthering our understanding by quantifying differential efficacy across the FAs.
Omega-3 and omega-6 fatty acids (FAs) are regarded as ‘essential’ polyunsaturated lipids because they cannot be synthesised within the body but must be obtained from the diet, and are required for normal growth and development. The parent omega-3 and omega-6 FAs are alpha-linolenic acid and linoleic acid, respectively. The human liver modifies these parent FAs into longer chain unsaturated fatty acids, with the key polyunsaturated FAs being eicosapentaenoic acid (EPA; omega-3), docosahexaenoic acid (DHA; omega-3) and arachidonic acid (omega-6). These are incorporated into phospholipids and, as cell membrane constituents throughout the body, mediate a range of physiological effects. Each of the FAs has differing properties and it is their optimal combination (particularly the omega-3 to omega-6 ratio) rather than any one FA ‘family’ contribution that impacts on health.