Alpha-Linolenic Acid: Is It Essential to Cardiovascular Health

There is a large body of scientific evidence that has been confirmed in randomized controlled trials indicating a cardioprotective effect for omega-3 fatty acids from fish. For alpha-linolenic acid (ALA), which is the omega-3 fatty acid from plants, the relation to cardiovascular health is less clear. We reviewed the recent literature on dietary ALA intake, ALA tissue concentrations, and cardiovascular health in humans. Short-term trials (6�12 weeks) in generally healthy participants mostly showed no or inconsistent effects of ALA intake (1.2�3.6 g/d) on blood lipids, low-density lipoprotein oxidation, lipoprotein(a), and apolipoproteins A-I and B. Studies of ALA in relation to inflammatory markers and glucose metabolism yielded conflicting results. With regard to clinical cardiovascular outcomes, there is observational evidence for a protective effect against nonfatal myocardial infarction. However, no protective associations were observed between ALA status and risk of heart failure, atrial fibrillation, and sudden death. Findings from long-term trials of ALA supplementation are awaited to answer the question whether food-based or higher doses of ALA could be important for cardiovascular health in cardiac patients and the general population. [Author�s abstract]
The estimated average ALA intake in the United States and most European countries is 1.3 to 1.7 g/d. The Institute of Medicine (IOM) of the National Academies established Dietary Reference Intakes for macronutrients in 2002. For ALA, the Adequate Intake (AI) was set at 1.6 g/d for men and 1.1 g/d for women.  Many advisory boards consider ALA intakes greater than 1.5 g/d important for human health. Several large, prospective cohort studies have shown inverse associations of ALA intake with risk of cardiovascular diseases, but other epidemiologic studies have been inconclusive. The trials reviewed in this paper consistently showed an increase in blood ALA levels after ALA supplementation, starting at low doses (<2 g/d). ALA supplementation also increased blood levels of EPA. Observational evidence indicates that a high ALA status may be related to a lower risk of metabolic syndrome. Long term treatment with high ALA doses had a beneficial effect on body weight and blood LDL cholesterol which warrants confirmation in future trials. [Editor�s comments]