Omega-3, Cardio Meta-Analysis “Cherry-Picked” Studies, Groups Say

The health community has become accustomed to hearing positive news linking omega-3 fatty acids to cardiovascular health. But researchers of a new meta-analysis published today in the Archives of Internal Medicine stated that “evidence remains inconclusive” of a positive effect.

For the final meta-analysis, the researchers selected 14 randomized, double-blind, placebo-controlled trials representing a total 20,485 patients with a history of cardiovascular disease. “Supplementation with omega-3 fatty acids did not reduce the risk of overall cardiovascular events…, all-cause mortality, sudden cardiac death, myocardial infarction, congestive heart failure, or transient ischemic attack and stroke. There was a small reduction in cardiovascular death…which disappeared when we excluded a study with major methodological problems,” the researchers wrote. “Our meta-analysis showed insufficient evidence of a secondary preventive effect of omega-3 fatty acid supplements against overall cardiovascular events among patients with a history of cardiovascular disease.”

Industry groups such as the Council for Responsible Nutrition (CRN; Washington, DC) and the Natural Products Association (NPA; Washington, DC) criticized the researchers for focusing mostly on small, short-term studies.

“This meta-analysis cherry-picked 14 randomized clinical trials (RCTs), most of which were small, short-term studies (less than one year of follow-up), leaving out other RCTs of longer length and greater relevance, all observational studies, and three (1-3) well-respected systematic reviews designed to look specifically at CVD outcomes,” stated Taylor Wallace, PhD, CRN’s senior director scientific and regulatory affairs, in a press release.

The groups encouraged consumers to consider this meta-analysis against the large body of historical data supporting omega-3 for heart health. “There is a wealth of evidence showing the benefits of omega-3 fatty acids on cardiovascular disease. This conclusion is not one that the scientific community has rushed to make. Rather, it is based on epidemiological and observational studies as well as clinical trials looking at a variety of cardiovascular disease outcomes,” stated Cara Welch, PhD, NPA’s vice president of scientific and regulatory affairs, to the press.

“Even the guest commentary that accompanies the meta-analysis notes that omega-3s are among the most extensively studied nutrients and adds that there is a large body of evidence showing the potential benefits of fish oil in cardiovascular health,” CRN’s Wallace stated. “Further, the commentary authors note the fact that the authors of the meta-analysis left out two large studies that could have altered their conclusion.”

NPA’s Welch continued, “For example, two large trials not included in this meta-analysis demonstrated significant benefits of fish oil supplementation. The GISSI-Prevenzione trial and the Japan EPA Lipid Intervention Study demonstrated that omega-3 supplements reduced the risk of death, nonfatal myocardial infarction, and nonfatal stroke, as well as major coronary events. A third trial, the GISSI-Heart Failure trial, found that fish oil supplementation reduced fatal cardiovascular disease.”  

Wallace remarked on the fact that the guest commentators support fatty fish but not omega-3 supplements, stating that fatty fish “…has no more (and some may say less) conclusive evidence than fish oil supplements in this area.”

References:

1. n-3 Fatty acids from fish or fish-oil supplements, but not alpha-linolenic acid, benefit cardiovascular disease outcomes in primary- and secondary-prevention studies: a systematic review.Wang C, Harris WS, Chung M, Lichtenstein AH, Balk EM, Kupelnick B, Jordan HS, Lau J.; Am J Clin Nutrition 2006;84:5-17

2. Omega-3 dietary supplements and the risk of cardiovascular events: a systematic review.Marik PE, Varon J.; Clin Cardiol 2009;32(7):365-372)

3. A Systematic Review of the Evidence Supporting a Causal Link Between Dietary Factors and Coronary Heart Disease. Andrew Mente, PhD; Lawrence de Koning, MSc; Harry S. Shannon, PhD; Sonia S. Anand, MD, PhD, FRCPC;  Arch Intern Med. 2009;169(7):659-669)