The complicated relationship between fish oil and heart health – Harvard Health Blog

For nearly two decades, the American Heart Association (AHA) has recommended that people with coronary heart disease (CHD) consume omega-3 fatty acids (the types of fatty acids found in fish and fish oil) to prevent a new heart attack. This recommendation was based on early randomized, controlled trials that found that fish oil supplementation was associated with a lower number of strokes, a heart attack, and death in people who already had a heart condition. On the other hand, the impact of fish oil supplements on the occurrence of a first heart attack or stroke (primary prevention) was never clearly demonstrated.

There have recently been major studies into the complex relationship between fish oil and heart health. The results are mixed and somewhat confusing, which makes both patients and doctors wonder: will fish oil supplements reduce my risk of heart disease?

What is the connection between fish oil and heart health?

How can omega-3 fatty acids in fish oil improve heart health? Several options have been proposed and are supported by animal research. These include protective mechanisms

  • stabilization of blood flow in and around the heart
  • reduction of triglycerides in the blood
  • lower blood pressure
  • prevention of blood clots
  • reduce inflammation.

Research into each of these is ongoing.

Many studies, varied results

Despite this data in animals, clinical studies in humans have not consistently supported the protective benefits of fish oil supplementation.

A meta-analysis published in JAMA Cardiology found no clear benefit for fish oil supplements in the prevention of heart disease or serious cardiovascular disease (CVD) in people with an increased risk of CVD.

This was followed by the publication of the ASCEND and VITAL studies, both with mixed results. In ASCEND, which examined diabetic patients with no known CHD, fish oil supplements did not reduce heart attacks or strokes, but significantly reduced the risk of death from a heart attack and stroke. VITAL investigated the effects of fish oil on primary prevention in people with a regular risk of heart disease, and also failed to find a significant reduction in all major CVD events. However, there were fewer heart attacks in subjects who took fish oil supplements, especially in those who did not eat fish.

The REDUCE-IT test was then published. This study looked at the effect of high-dose fish oil supplements on people with high blood levels of triglycerides who had an increased risk of CVD. In contrast to previous studies, REDUCE-IT found a significant reduction in cardiovascular events in subjects using the high dose of fish oil supplements. While most studies tested 1 gram or less of fish oil with a combination of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), REDUCE-IT only used a dose of 4 grams of EPA. (Vascepa, a prescription version of the EPA fish oil supplement used in REDUCE-IT, has been approved by the FDA for the treatment of very high triglyceride levels of 500 mg / dl or higher. In November, the FDA extended the approval of Vascepa; can now be prescribed to reduce the risk of cardiovascular events such as heart attack and stroke.)

A repeat of the JAMA Cardiology meta-analysis, but now with 13 tests instead of the original 10, was published in the Journal of the American Heart Association in October 2019. The addition of these three tests increased the sample size by almost 65%, from 77,917 participants in the study to 127,477 participants. When re-analyzing the extensive data, researchers discovered that fish oil omega-3 supplements reduced the risk of heart attack and cardiovascular death. There was no effect on stroke. Interestingly enough, risk reductions were found to be linearly related to the omega-3 dose. In other words, the higher the dose, the greater the risk reduction.

What does this mean to you?

Omega-3 supplements from fish oil appear to be heart healthy and have a protective effect on CHD. But before we all start looking for supplements, it might be worth taking a heart-healthy diet full of fresh fruits and vegetables, with lean proteins such as fish, as recommended by the AHA. For those of us at highest risk, especially those with elevated triglyceride levels, it is worth talking to your doctor about high doses of EPA fish oil supplements.


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