Oily fish reduces plasma triacylglycerols: a primary prevention study in overweight men and women

Objective Previous studies have demonstrated benefits of high-dose long-chain ω-3 polyunsaturated fatty acid (LC ω-3 PUFA) supplements on metabolic risk. Effects of increased dietary ω-3 PUFA, via oily fish and/or plant-derived ω-3 PUFAs, are less clear and may be modulated by the ω-6:ω-3 PUFA of the habitual diet. This study examined the effect on cardiovascular disease risk markers of reducing dietary ω-6:ω-3 PUFA by changes in linoleic acid:α-linolenic acid (LA:LNA) and/or increasing LC ω-3 PUFA. It tested whether decreases in LA:LNA modulate effects of LC ω-3 PUFA. Methods One hundred forty-two subjects, recruited to a 24-wk randomized study, were assigned to a control group or one of four interventions. Intervention groups received two portions of oily fish (4.5 g eicosapentaenoic acid + docosahexanoic acid) or white fish (0.7 g eicosapentaenoic acid + docosahexanoic acid) per week, and replaced habitual household fats with ones high in sunflower (high LA:LNA) or rapeseed (low LA:LNA) oil. Results Modest dietary manipulations of ω-6 and ω-3 PUFAs resulted in significant group × time interactions for serum triacylglycerols (TAGs; P = 0.05); at 24 wk the control and two oily fish groups showed lower TAG than did the white fish/sunflower group (P = 0.05). Reductions in TAG, associated with increased oily fish intakes, were maximized when combined with lower dietary LA:LNA. There were no significant changes in several other cardiovascular disease risk markers. Conclusions Two portions of oily fish per week led to significant reductions in TAG relative to consumption of two portions of white fish per week. Changes in TAG were maximized when combined with lower LA:LNA.