Key Findings:
This meta-analysis of prospective studies found that dietary ALA can lower the risk of fatal coronary heart disease through in part by reducing cardiac arrhythmia. In this study, there were also indications for an increased risk of prostate cancer in men with a high intake of ALA compared with those with a low intake. Subsequent research suggests however that the relationship may be spurious and confounded by advanced disease states and levels of saturated fat in the diet. However the authors do suggest that the protective effect of ALA on fatal coronary heart disease would probably outweigh any possible negative effects, especially for men with an increased risk of heart disease. In some countries, meat and not vegetable oil is the major source of ALA. The effects of ALA could therefore be caused by high meat intake instead of high ALA intake.
ABSTRACT:
The objective of this meta-analysis was to estimate quantitatively the associations between intake of α-linolenic acid [ALA, the (n-3) fatty acid in vegetable oils], mortality from heart disease, and the occurrence of prostate cancer in observational studies. We identified 5 prospective cohort studies that reported intake of ALA and mortality from heart disease. We also reviewed data from 3 clinical trials on ALA intake and heart disease. In addition, we identified 9 cohort and case-control studies that reported on the association between ALA intake or blood levels and incidence or prevalence of prostate cancer. We combined risk estimates across studies using a random-effects model. High ALA intake was associated with reduced risk of fatal heart disease in prospective cohort studies (combined relative risk 0.79, 95% CI 0.60–1.04). Three open-label trials also indicated that ALA may protect against heart disease. However, epidemiologic studies also showed an increased risk of prostate cancer in men with a high intake or blood level of ALA (combined relative risk 1.70; 95% CI 1.12–2.58). This meta-analysis shows that consumption of ALA might reduce heart disease mortality. However, the association between high intake of ALA and prostate cancer is of concern and warrants further study. (Author’s abstract)
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