Alpha-linolenic acid reduces risk of nonfatal MI 

Boston, MA – The consumption of a diet containing vegetable oils rich in alpha-linolenic acid (ALA) is associated with significant reductions in the risk of nonfatal MI, a new study has shown [1]. Investigators say the protective effect of ALA is evident among individuals with low intakes, suggesting the greatest benefit might be in developing countries, where fatty-acid consumption is limited.

"The potential for benefit is great when the baseline intake is low," said lead investigator Dr Hannia Campos (Harvard Medical School, Boston, MA). "In countries where people eat very little fish—and some of these countries have almost no sources of omega-3 fatty acids because they cook with corn or sunflower oils—the consumption of vegetable oils with ALA could have a major impact on heart disease."

In an editorial accompanying the published study [2], Dr William Harris (University of South Dakota, Sioux Falls) said that the data are suggestive and would be good news for individuals who will not or cannot eat fish, but more studies are still needed. "If ALA were able to do the same 'heavy lifting' that [eicosapentaenoic acid] EPA and [docosahexaenoic acid] DHA do, this would be welcomed news, because the capacity to produce ALA is essentially limitless, whereas there are only so many fish in the sea," he writes.

The results of the study and editorial are published online July 8, 2008 in Circulation.

Benefit is great when the baseline levels are low

ALA is an intermediate-chain n-3 polyunsaturated fatty acid that is often overshadowed by the more famous long-chain members of the n-3 family, namely EPA and DHA acids that are found in fish oils. ALA intake has increased during the past several decades, however, mainly through the consumption of vegetable oils such as soybean, canola, and flaxseed oil. Speaking with heartwire, Campos said some studies have shown that low ALA intake was associated with a risk of coronary heart disease and sudden cardiac death, and others, although not all, have suggested an inverse association between ALA consumption and risk of MI.

In this study, 1819 patients who survived an MI provided samples of adipose tissue for analysis of fatty-acid stores and completed a validated food questionnaire, with 1817 matching controls doing the same. ALA in the adipose tissues ranged from 0.36% in the lowest decile to 1.04% in the highest decile. The corresponding median levels for ALA intake were 1.11 g/day to 2.35 g/day.

In a multivariate model that included smoking, physical activity, history of diabetes, hypertension, fat intake, and waist-to-hip ratio, among others, there was an observed inverse relationship between adipose tissue ALA and dietary ALA intake and risk of nonfatal MI.