Background: Recent evidence supports the protective effects of n-3 (omega-3) fatty acids (n-3 FAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on vascular function.

Objective: We investigated the effects of EPA and DHA on postprandial vascular function in subjects with type 2 diabetes mellitus.

Design: In a double-blind, placebo-controlled, randomized, crossover manner, 34 subjects with type 2 diabetes mellitus received daily either 2 g purified EPA/DHA (termed n-3 FAs) or olive oil (placebo) for 6 wk. At the end of this period, we measured macrovascular (brachial ultrasound of flow-mediated dilatation; FMD) and microvascular [laser-Doppler measurements of reactive hyperemia (RH) of the hand] function at fasting and 2, 4, and 6 h after a high-fat meal (600 kcal, 21 g protein, 41 g carbohydrates, 40 g fat).

Results: Fasting vascular function remained unchanged after n-3 FAs and placebo. Postprandial FMD decreased from fasting after placebo, with a maximum decrease (38%) at 4 h-an effect that was significantly reduced (P = 0.03 for time x treatment interaction) by n-3 FA supplementation (maximum decrease in FMD was at 4 h: 13%). RH remained unchanged after placebo, whereas it improved significantly (P = 0.04 for time x treatment interaction) after n-3 FA supplementation (maximum increase was at 2 h: 27%).

Conclusions: In subjects with type 2 diabetes mellitus, 6 wk of supplementation with n-3 FAs reduced the postprandial decrease in macrovascular function relative to placebo. Moreover, n-3 FA supplementation improved postprandial microvascular function. These observations suggest a protective vascular effect of n-3 FAs.