Effect of low doses of n-3 fatty acids on cardiovascular diseases in 4,837 post-myocardial infarction patients: design and baseline characteristics of the Alpha Omega Trial

Background: Weekly fish consumption has been related to a lower risk of fatal coronary heart disease (CHD) and incident stroke in populations with a low fish intake. This relation has mainly been attributed to n-3 fatty acids in fish, that is, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). It is at present unclear whether alpha-linolenic acid (ALA), a n-3 fatty acid from vegetable origin, could also be protective against cardiovascular diseases (CVDs). There is a need for food-based trials to establish the efficacy of low doses of n-3 fatty acids in CVD prevention.

Objectives: The aim of the study was to evaluate the effect of an additional daily intake of 400 mg of EPA + DHA and 2 g of ALA on CVD morbidity and mortality in free-living subjects with a history of myocardial infarction.

Design: The multicenter Alpha Omega Trial is a randomized, double-blind, placebo-controlled trial with a 2 x 2 factorial design. Between May 2002 and December 2006, we enrolled a total of 4,837 men and women aged 60 through 80 who experienced a myocardial infarction within 10 years before entering the study. Subjects were randomized to 1 of 4 margarine spreads that were enriched with EPA + DHA and/or ALA, or placebo. Compliance was monitored via tub counts and assessment of n-3 fatty acids in plasma. Subjects were observed for 40 months for the occurrence of fatal and nonfatal CVD.

Results: The cohort was on average 69 years old at the start of the study and comprised 22% women. Subjects had their (last) myocardial infarction approximately 4 years before enrollment. Mean body mass index was 27.7 kg/m(2), and 17% smoked. Average serum total and high-density lipoprotein cholesterol were 4.7 and 1.3 mmol/L, respectively, and 85% used statins. Mean blood pressure was 142/80 mm Hg, and most subjects were on antihypertensive medication (88%). Diabetes mellitus was reported by 17% of the subjects, and 7% reported a history of stroke. The overall mortality rate during the trial period was 23 per 1,000 person-years, with approximately 40% due to CVD.

Current status: Follow-up of the patients was completed in November 2009, and findings will be reported in the second part of 2010.