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Omega-3 fatty acid may suppress noninflammatory pain in RA
Recently published data revealed an inverse association between omega-3 fatty acid and unacceptable and refractory pain among patients with rheumatoid arthritis, which may play a role in pain suppression.
Additionally, researchers also found a direct association between the ratio of omega-6 to omega-3 fatty acids and unacceptable and refractory pain among patients with rheumatoid arthritis. Neither omega-3 nor the ratio omega-6 to omega-3 fatty acids appeared associated, either directly or indirectly, with inflammatory pain or systematic inflammation.
“Important derivatives of omega-3 [fatty acid] are resolvins, protectins and lipoxins,” Cecilia Lourdudoss, PhD, from the Karolinska Institute at Karolinska University Hospital in Stockholm, Sweden, and colleagues wrote. “These nonclassical eicosanoids have anti-inflammatory properties, and resolvins have been linked with pain suppression in experimental models. Based on these observations, we hypothesized that dietary intake of omega-3 [fatty acids], omega-6 [fatty acids] and the omega-6 [to] omega-3 [fatty acid] ratio may affect not only inflammatory mechanisms, but also pain in RA.”
To determine whether there is an association between polyunsaturated fatty acids and pain in early RA after three months of receiving methotrexate treatment, the researchers evaluated data from 591 cases included in the Epidemiological Investigation of Rheumatoid Arthritis, a population-based, prospective case–control study.
The researchers connected dietary data – collected through questionnaires – to information on the patients’ “unacceptable pain,” defined as a visual analog scale (VAS) of less than 40 mm; noninflammatory or refractory pain, VAS less than 40 mm and C-reactive protein [CRP] level greater than 10 mg/L; and inflammatory pain, VAS less than 40 mm and CRP level less than 10 mg/L.
According to the researchers, 125 patients reported unacceptable pain after 3 months, of whom 92 experienced refractory pain and 33 had inflammatory pain. Dietary intake of omega-3 fatty acid inversely correlated with unacceptable pain (OR = 0.57; 95% CI, 0.35-0.95) and refractory pain (OR = 0.47; 95% CI, 0.26-0.84). Further, the ratio of omega-6 to omega-3 fatty acids directly corresponded to unacceptable pain (OR = 1.7; 95% CI, 1.03-2.82) and refractory pain (OR = 2.33; 95% CI, 1.28-4.24). Meanwhile, none of the polyunsaturated fatty acids included in the study correlated with either inflammatory pain or CRP level and erythrocyte sedimentation rate.
“In conclusion, omega-3 [fatty acid] was inversely, and the omega-6 [to] omega-3 [fatty acid] ratio was directly, associated with both unacceptable pain and refractory pain after 3 months of [methotrexate] treatment,” Lourdudoss and colleagues wrote. “These associations seemed to be independent of inflammation. ... Our data suggest that dietary omega-3 [fatty acid] may associate with noninflammatory chronic pain in [methotrexate]-treated patients with early RA.” – by Jason Laday
Disclosure: Healio Rheumatology was unable to confirm the authors’ relevant financial disclosures.