Omega-3 From Fish, Plant Sources May Lower Risk of Fatal MI

Marlene Busko

July 07, 2016

STANFORD, CA — A pooled study of 19 international cohorts of middle-aged and older people with no prior heart disease found that higher levels of omega-3 polyunsaturated fatty acids (PUFAs) were linked with a lower risk of having a fatal cardiac event within 10 years, but this was not true for nonfatal MI[1].

Specifically, for every 1-standard-deviation increase in levels of seafood-derived docosapentaenoic acid (DPA), docosahexaenoic acid (DHA), or plant-derived α-linolenic acid (ALA), individuals had a significant approximately 9% lower risk of death from MI during follow-up. The risk was similarly reduced, although it was not significant, with seafood-derived eicosapentaenoic acid (EPA).

The study by Dr Liana C Del Gobbo (Stanford University School of Medicine, CA) and colleagues was published June 25, 2016 in JAMA Internal Medicine.

These findings are consistent with "evidence from experimental models and animal studies that show a major effect of these seafood-based omega-3 fatty acids is to stabilize heart membranes and reduce the risk of ventricular fibrillation—but not plaque rupture," Del Gobbo told heartwire from Medscape.

"It's important to highlight that people were consuming these omega-3s primarily from food" and supplement intake was virtually nil, she stressed. Fatty-fish sources of omega-3 PUFAs include salmon, rainbow trout, anchovies, and sardines, and good sources of ALA include certain nuts (especially walnuts), flaxseed, certain vegetable oils (especially canola oil), and soybeans, she noted.

This study suggests that clinicians should encourage patients to eat a heart-healthy diet of "at least two to three servings of fatty fish a week, which is consistent with recommendations from the American Heart Association," said Del Gobbo.

"But of course we want to encourage people to also eat their fruits and vegetables and whole grains," she said. This and other studies "all suggest that fatty fish and nuts and healthy oils should be emphasized, which are also part of a healthy Mediterranean-diet pattern. Our study reinforces some of those food sources."

Omega-3 Biomarker Levels and Subsequent Cardiac Events

Previous studies that looked at whether fish-oil supplements might lower the risk of cardiac events reported mixed results, but some patients had preexisting CAD or were eating foods high in omega-3, and most studies were based on self-reported diet recall with a potential for bias, according to the researchers.

They aimed to investigate the link between blood levels of omega-3 PUFAs and incident nonfatal MI or fatal CHD (fatal MI, CHD death, or sudden cardiac death) using pooled data from 19 international cohorts. The cohorts were part of the Fatty Acids and Outcomes Research Consortium (FORCE), which in turn was drawn from the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Fatty-Acids Working Group.

They analyzed data from 45,637 participants from 16 countries (Australia, Costa Rica, Finland, France, Germany, Ireland, Israel, Italy, Norway, Russia, Singapore, Spain, Sweden, Switzerland, the United Kingdom, and the United States) who had blood tests for fatty acids. The patients (63% male) had a mean age of 59 (range 18 to 97 years) and had no prior history of MI, angina, coronary revascularization, or stroke.

During a median 10-year follow-up there were 7157 nonfatal MIs and 2781 fatal CHD events.

Risk of a Fatal Cardiac Event During Follow-up

Type of omega-3 PUFA Relative risk (95% CI) *
ALA 0.91 (0.84–0.98)
DHA 0.90 (0.84–0.96)
DPA 0.90 (0.85–0.96)
EPA 0.91 (0.82–1.00)
*Relative risk for each 1-standard-deviation increase in the level of different types of omega-3 polyunsaturated fatty acids (PUFAs), after multivariable adjustments

"This investigation provides the most comprehensive estimates to date of the associations between seafood and plant-based ω-3 PUFAs, assessed using biomarkers, and primary incidence of CHD in generally healthy, free-living populations around the world," the researchers summarize, and it shows that these omega-3 PUFAs "are associated with a modestly lower incidence of fatal CHD.

"Combined with relative affordability, global accessibility, and sustainability of ALA, [the findings also] support the potential importance of ALA for improving global cardiovascular health," they suggest.

The funding of the 19 studies is listed in the article. Del Gobbo reported receiving ad hoc consulting fees from the Life Sciences Research Organization. Disclosures for the coauthors are listed in the article.

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