Habitual Diets Rich in Dark-Green Vegetables Are Associated with an Increased Response to ω-3 Fatty Acid Supplementation in Americans of African Ancestry

Although substantial variation exists in individual responses to omega-3 (omega-3) (n-3) fatty acid supplementation, the causes for differences in response are largely unknown. Here we investigated the associations between the efficacy of omega-3 fatty acid supplementation and a broad range of nutritional and clinical factors collected during a double-blind, placebo-controlled trial in participants of African ancestry, randomly assigned to receive either 2 g eicosapentaenoic acid (EPA) + 1 g docosahexaenoic acid (n = 41) or corn/soybean oil placebo (n = 42) supplements for 6 wk. Food-frequency questionnaires were administered, and changes in erythrocyte lipids, lipoproteins, and monocyte 5-lipoxygenase-dependent metabolism were measured before and after supplementation. Mixed-mode linear regression modeling identified high (n = 28) and low (n = 13) omega-3 fatty acid response groups on the basis of changes in erythrocyte EPA abundance (P < 0.001). Compliance was equivalent (similar to 88%), whereas decreases in plasma triglycerides and VLDL particle sizes and reductions in stimulated monocyte leukotriene B-4 production were larger in the high-response group. Although total diet quality scores were similar, the low-response group showed lower estimated 2005 Healthy Eating Index subscores for dark-green and orange vegetables and legumes (P = 0.01) and a lower intake of vegetables (P = 0.02), particularly dark-green vegetables (P = 0.002). Because the findings reported here are associative in nature, prospective studies are needed to determine if dietary dark-green vegetables or nutrients contained in these foods can enhance the efficacy of omega-3 fatty acid supplements. This trial was registered at clinicaltrials.gov as NCT00536185.