“Dietary fish oils, rich in long-chain n–3 fatty acids [e.g., docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)], modulate inflammatory reactions through various mechanisms, including gene expression, which is measured as messenger RNA concentration.”
“We wanted to determine the effects of 6 months of dietary supplementation with an n–3 FA preparation rich in DHA on global DNA methylation of peripheral blood leukocytes and the relation to plasma EPA and DHA concentrations in Alzheimer disease patients.”

“Patients originated from the randomized, double-blind, placebo-controlled OmegAD study, in which 174 Alzheimer patients received either 1.7g DHA and 0.6g EPA or placebo daily for 6 months.”

“At 6 months, the n–3 FA group displayed marked increases in DHA and EPA plasma concentrations (2.6- and 3.5-fold), as well as decreased methylation in 2 out of 4 CpG sites, respectively.”

“Supplementation with n–3 FA for 6 months was associated with global DNA hypomethylation in peripheral blood leukocytes. Our data may be of importance in measuring various effects of marine oils, including gene expression, in patients with Alzheimer disease and in other patients taking n–3 FA supplements.”

K.Mohsen, et al
DHA-rich n–3 fatty acid supplementation decreases DNA methylation in blood leukocytes: the OmegAD study
American Journal Of Clinical Nutrition — Volume 106 #4 — October 2017 — page 1157