The trial randomised 67 patients to either a diet high in omega 3 long chain poly-unsaturated fatty acids and low in omega 6 linoleic acid (H3/L6) or a diet low in (L6).
Most participants were women, average age of 42 years, who had headaches at least four hours per day for a minimum of 15 days per month for three months or more and a headache history of over two years under physician headache management.
The primary study results, published in the journal Pain, show that at 12 weeks, both groups had significant improvements in all clinical outcomes, but the improvements were significantly greater in those on the H3/L6 diet.
Moreover, significantly fewer patients on the H3/L6 diet used any pain-related acute or adjunctive medication at the end of the study compared with baseline.
In the secondary analysis of the data the researchers specifically looked at the effect of the interventions on psychological distress and health related quality of life (HRQOL) of the headache sufferers.
They found that the H3/L6 group experienced statistically significant reductions in psychological distress and improvements in HRQOL. This was not seen in the L6 group.
Overall, the lipid mediators derived from the omega 6 polyunsaturated fatty acid known as arachidonic acid are pro-inflammatory and pronociceptive (increase pain), while omega 3s (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) - found in fish oil) give rise to several compounds (resolvins, protectins and maresins) that are anti-inflammatory, pro-resolving and pain-reducing.
The present study researchers suggest that the reductions in physical pain seen in the H3/L6 group may be due to diet-induced alteration in the balance of pronociceptive and antinociceptive mediators derived from omega 6 and omega 3 fatty acids. However, the effect on mood may not be as straight-forward.
Several randomised-controlled trials have shown substantial reductions of depressive symptoms with omega 3 supplement interventions. While meta-analyses have reported that EPA-predominant omega 3 supplements may lead to reductions in depressive symptoms among subjects with clinically significant depressive illnesses.
The present study researchers postulate that given the marked reduction in physical pain in the H3/L6 group in the CDH trial, the concomitant reduction in subjects’ psychological distress may not be surprising.
However, they note that it is not clear whether the reduction in psychological distress was secondary to relief of physical pain, or to a more direct mechanism affecting psychological aspects of pain experience.
They recommend further studies be undertaken to better understand the role this type of targeted dietary manipulation could play in the management of psychological distress and physical impairment that often accompany chronic pain.