Effects of stearidonic acid on serum triacylglycerol concentrations in overweight and obese subjects: a randomized controlled trial

BACKGROUND/OBJECTIVES: Eicosapentaenoic acid (EPA), which may reduce the risk for coronary heart disease (CHD), can be synthesized at low rates from alpha-linolenic acid (ALA). The rate-limiting step for this conversion is the Delta 6-desaturation of ALA into stearidonic acid (SDA). Thus providing oils rich in SDA may increase endogenous synthesis of EPA, which may subsequently lower serum triacylglycerol concentrations, an effect frequently observed after EPA supplementation. We therefore studied the effects of Echium oil on serum triacylglycerol concentrations and the omega-3 index, which correlate negatively with the risk for CHD. SUBJECTS/METHODS: A randomized, double-blind, placebo-controlled crossover trial was conducted, in which 36 healthy overweight and slightly obese subjects daily received 10 g of Echium oil (providing 1.2 g of SDA) or a high oleic acid sunflower oil (HOSO) as control for 6 weeks, with a washout period of at least 14 days. Four subjects dropped out. Differences between periods were tested for statistical significance (P < 0.05) using a paired t-test. RESULTS: Serum triacylglycerol and other lipid concentrations were not significantly affected by consumption of Echium oil compared with HOSO. Echium oil significantly increased percentage of EPA in red blood cell (RBC) membranes with 0.14 +/- 0.25% (mean +/- s.d.) compared with HOSO (P=0.02). No significant effects on docosahexaenoic acid in RBC membranes or on the omega-3 index were found. CONCLUSIONS: In healthy overweight and slightly obese subjects, an increased intake of SDA from Echium oil does not lower serum triacylglycerol concentrations. Despite an increase in the percentage of EPA in RBC membranes, the omega-3 index was not changed.