Background – Increased consumption of the long chain omega-3 (n-3) fatty acids eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) is associated with a reduction in cardiovascular (CV) and inflammatory risk factors but it is unclear what level of intake is required to achieve benefits.
Objective – The aim of this study was to establish a relationship between changes in red blood cell (RBC) membrane DHA levels and changes in CV and inflammatory risk factors.
Design – Seventy subjects (42 males and 28 females, mean age 51.8 yr) with habitually low dietary n-3 intake, 2
elevated triglycerides (> 1.6 mmol) and BMI > 25 kg/m were enrolled in a randomized, double-blind, placebo- controlled intervention trial. Subjects were assigned to consume 6 x 1g oil capsules per day for 12 weeks. Varying combinations of DHA-rich tuna oil (26% DHA, 6% EPA) or sunflower oil (placebo) capsules provided intakes of 0, 2, 4 or 6g of either oil/day. RBC membrane fatty acid composition and markers of CV risk and inflammation were measured.
Outcomes – DHA incorporation into RBC membranes increased over 12 weeks and was proportional to the level of DHA consumed (P<0.05). After 6 weeks of supplementation, there was a dose-response relationship between the intake of DHA and reduction in plasma triglycerides (R=0.315, P<0.05), with no effect on plasma cholesterol. Conclusions – Plasma triglycerides are reduced in a dose-dependent manner in response to supplementation with DHA-rich fish oil. The relationship between the intake of DHA, its incorporation into RBC membranes and changes in markers of cardiovascular risk may provide a potential index of the health benefits of DHA rich foods.