Two servings of fatty fish every week — does it help your heart?

Nearly 30 years ago, I attended an American Heart Association meeting and sat in on a presentation about fatty fish in the diet. The presenter claimed that two servings of fatty fish helped reduce the risk of cardiovascular events such as stroke, heart attack, and other issues.

This presentation occurred way before I made a presence on the internet debunking nutritional claims. I thought that the researchers behind the study were smarter than me, so who am I to dismiss their claims? Plus, I enjoy fatty fish with my sushi, salmon, and lox with my bagels. I mean, I was already practicing the diet, so my cardiovascular system must be working well.

The study was eventually published, and it became gospel in the cardiology world. Everyone who had anything to do with cardiology — physicians, researchers, cardiovascular device manufacturers — jumped on board with their two servings of fatty fish.

Then I grew up to be a cranky, snarky skeptic. And I wondered if this recommendation was actually supported by science. And that’s when the foundation of this belief that I held crumbled very quickly.

sashimi in bowl
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The fatty fish studies

One of the best reviews on the topic, published in Circulation on 19 November 2002, seemed to show that omega-3 fatty acids, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are found in fatty fish, reduced the incidence of cardiovascular disease. In essence, individuals with a higher intake of omega-3 fatty acids, along with a higher red blood cell level of EPA and DHA, have a lower risk of cardiovascular disease.

You know I am a fan of large systematic reviews, so this seems so convincing. However, this evidence for fatty fish in the diet was based mostly on observational studies rather than several large double-blind, randomized clinical trials.

I don’t want to sound like a hypocrite, so I don’t dismiss observational studies as being useless. For studies that involve drugs, case-control and cohort observational studies provide robust evidence for safety and effectiveness. We use these studies to support the settled science that vaccines are safe and effective.

But as I grew up as a skeptic, I find numerous issues with observational studies with nutrition claims. There are so many confounding variables, that it begins to get harder and harder to determine causality between the diet and the expected outcome.

bagel with salmon
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Getting skeptical

Several years ago, I reviewed studies of omega-3 fatty acids (including EPA and DHA).

In 2012, two separate meta-analyses (the best kind of evidence available) of these studies were published – the first one analyzed only those studies which included individuals with a history of heart disease, and the other one analyzed studies of individuals both with and without a history of heart disease. Neither meta-analysis found convincing evidence of protective benefits for omega 3 fish oil supplementation.

A new systematic review (considered the pinnacle of the hierarchy of biomedical research), published in the Cochrane Database of Systematic Reviews, seems to indicate that there isn’t much value in omega-3 supplements for preventing cardiovascular disease. The study included 79 randomized controlled trials that lasted greater than 12 months. Over 112,000 patients were included in these studies. In addition, the study participants were from  Asia, Europe, North America, and Australia.

The study showed no effect of omega-3 supplements on the following cardiovascular outcomes:

  • All-cause mortality, risk ratio (RR) of 0.98.
  • Cardiovascular mortality, RR = 0.95.
  • Cardiovascular events (stroke, heart attack, and other related events), RR=0.99.
  • Coronary heart disease mortality, RR=0.93.
  • Stroke, RR=1.06.
  • Atrial fibrillation, RR=1.06.

In other words, omega-3 supplements, a proxy for fatty fish, showed no statistical difference in risks of cardiovascular disease over those who did not consume them.

The Skeptical Cardiologist, Anthony C. Pearson, MD, recently wrote about his change of heart about fatty fish and cardiovascular disease:

By early 2021, based on several new trials of fish oil supplements, I concluded that “there is no compelling evidence for you to take over-the-counter fish oil supplements for primary or secondary prevention of cardiovascular disease.” This is the same advice I have been giving since 2013.

The STRENGTH study, which showed absolutely no benefit of supplementing with EPA/DHA on reducing a composite cardiovascular endpoint, has triggered me to start looking more closely at the quality and strength of the evidence for the fish recommendations in general.

The PURE study found no significant association between fish intake and any health outcome after adjustment for known confounders.

These findings and an old Welsh randomized trial have caused me to question whether eating fish does, indeed, protect us against atherosclerotic complications like stroke and heart attack.

Risks of consuming fatty fish

Adding to the limited and contradictory evidence that fatty fish probably does not have a benefit in preventing CVD is the fact that there is a safety issue in consuming so much fatty fish. The FDA makes recommendations about consuming fish, especially those fishes that may have higher levels of mercury.

In other words, consuming a lot of fatty fish has some risks for what appear to be limited benefits, especially concerning cardiovascular diseases.

I am not recommending that you stop eating fatty fish, especially if you enjoy it. But, it appears that the health benefits were vastly overrated and based upon some weak observational studies. Go ahead, eat your sushi and salmon steaks for their taste and flavor, but don’t expect that they are going to make your cardiovascular system powerful.

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The Original Skeptical Raptor
Chief Executive Officer at SkepticalRaptor
Lifetime lover of science, especially biomedical research. Spent years in academics, business development, research, and traveling the world shilling for Big Pharma. I love sports, mostly college basketball and football, hockey, and baseball. I enjoy great food and intelligent conversation. And a delicious morning coffee!