Friend or Foe: Casting doubt on fish oil’s heart health role

You may have seen a startling headline recently claiming that regular use of fish oil supplements may harm heart health.

In so many words, headlines claim that controversial research published in BMJ Medicine indicates that taking fish oil supplements increases the risk of stroke and heart disease in healthy people.

It certainly caught my attention because it goes against years of scientific literature I’ve read that seemed to show quite the opposite — including research in 2021 that was on the side of omega-3’s potential to open the door to more targeted stroke prevention…

Not to mention that the pooled data of 17 studies that showed people with high blood levels of omega-3s live longer than those with less.

And what about those “official” dietary recommendations…

It was just in 2018 when the American Heart Association issued a scientific statement advising the consumption of one to two seafood meals per week to reduce the risk of congestive heart failure, coronary heart disease, ischemic stroke and sudden cardiac death. 

But, of course, too few of us eat enough fish regularly, much less fatty fish, that even doctors have taken to prescribing fish oil supplements to their patients.

However, it’s not hard to see where the confusion over supplementing comes from. For example, in 2018, a review of research on the heart-health benefits of omega-3 supplements found that they didn’t provide much (if any) benefit. But two studies published in 2019 found the opposite…

One of those studies found fish oil supplements reduce the risk of heart attack and coronary heart disease by 8 percent. The other study also found that omega-3s provide cardiovascular benefits, but this time the benefits came with one condition — you have to get your omega-3 Index (blood level) to 8 percent or higher.

That’s not surprising — and more studies have confirmed the amount taken can make a difference… in a brain health study they also found omega-3 dosage mattered… and another study zeroed in on optimum dosage for lowering blood pressure.

And as we’ll see yet again, the devil is in the details — especially when it comes to drawing conclusions from scientific research…

Supplementing fish oil: friend or foe

A prospective cohort study is a type of observational study following a group of people who are alike in many ways, over a specified amount of time. In this instance, researchers in China followed almost 416,000 people, aged 40 to 69, who self-reported their use of fish oil supplements at the beginning of a study. The study lasted four years with an 11.9-year follow-up.

It’s important to mention a few things about the questionnaire and interview given to the participants at the beginning of the study…

• Only one question was asked of the participants about taking fish oil supplements — and it was a yes/no question.
• They did not identify the type, quality or dosage of the fish oil supplements — which as we’ve learned from other studies, dosage can especially make quite a difference.
• Nor was any information asked or gathered about whether participants changed anything about their supplementing habit — or stopped supplementing completely — during the course of study or at the end.

After all was said and done, the researchers concluded that regular use of fish oil supplements might increase, rather than lessen, the risk of first-time heart disease and stroke among those in good cardiovascular health — but may slow the progression of existing poor cardiovascular health and lower the risk of death.

Specifically, among those with no known cardiovascular disease at the start of the monitoring period, regular use of fish oil supplements was associated with a 13% heightened risk of developing atrial fibrillation and a 5% heightened risk of having a stroke.

But among those who had cardiovascular disease at the start of the monitoring period, regular use of fish oil supplements was associated with a 15% lower risk of progressing from atrial fibrillation to a heart attack and a 9% lower risk of progressing from heart failure to death.

These discoveries led the research team to conclude that “Regular use of fish oil supplements might have different roles in the progression of cardiovascular disease. Further studies are needed to determine the precise mechanisms for the development and prognosis of cardiovascular disease events with regular use of fish oil supplements.”

They also acknowledged that since their study was observational, no conclusion could be drawn about causal factors. In other words, their study could not confirm if supplementing fish oil contributed to the findings.

What do health experts say

Dr. Ronald Hoffman is a respected integrative medical expert and host of the Intelligent Medicine radio show and podcast. In an interview published at Integrative Practioner, he shared his thoughts.

“The magnitude of risk of Afib among the participants who took the fish oil was small — 13 percent, which is hardly enough to warrant the conclusion that regular use of fish oil supplements increases the risk of Afib and stroke. The risk of stroke was very slight and did not distinguish between thrombotic versus hemorrhagic strokes. While it’s plausible that fish oil’s blood-thinning effects might lead to more hemorrhagic strokes, it’s also possible that those strokes were a consequence of new-onset Afib in non-anti-coagulated individuals.”

He also added “As with much nutritional epidemiology, it’s hard to tease out the impacts of uncontrolled variables on the outcomes.  For example, it’s possible that the participants in the fish oil group were taking it because of health issues. Also, the cohort of fish oil users were older and predominantly white females, which are potential confounders.”

Deeper analysis revealed that other variables or confounders, including age, sex, consumption of non-oily fish, high blood pressure and the use of blood pressure-lowering drugs and statins changed the associations observed.

Dr. Hoffman shared that this latest study will not influence how he prescribes fish oil to his patients — and I would imagine many other physicians feel the same way, considering the depth of positive research, safety and efficacy about the effects of omega-3s on heart health…

“For patients at high risk of stroke, it seems counterintuitive to recommend administering prescription blood thinners for prevention while withholding fish oil that also confers anti-thrombotic benefits,” said Dr. Hoffman. “For patients with Afib, this study demonstrated that fish oil supplementation provided a modest degree of protection from death, so those patients should certainly take a fish oil supplement.

“I’m encouraged by this study’s findings, which substantiate omega-3s benefits in people with known cardiovascular disease or those who have high-risk factors, which comprises a sizeable percentage of the adult American population,” concluded Dr. Hoffman. “For the average healthy person, the harm in taking fish oil supplements is minimal or non-existent, and the benefits are many.”

Sources:

Regular fish oil supplement use might boost first time heart disease and stroke risk — EurekAlert

Can Regular Use of Fish Oil Supplements Harm Heart Health? — Integrative Practitioner

Regular use of fish oil supplements and course of cardiovascular diseases: prospective cohort study — BMJ Journals