The complicated relationship between fish oil and heart health

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For nearly two decades, the American Heart Association (AHA) has recommended that people with coronary artery disease (CHD) consume omega-3s (the fatty acids found in fish and fish oil) to prevent another heart attack. This recommendation was based on early randomized controlled trials that found that supplementing with fish oil was associated with lower rates of stroke, heart attack, and death in people who previously had heart disease. On the other hand, the influence of fish oil supplements on preventing a first heart attack or stroke (primary prevention) has never been clearly demonstrated.

Large studies have recently been conducted examining the complex relationship between fish oil and heart health. The results were mixed and somewhat confusing, leaving both patients and doctors to wonder: will fish oil supplements reduce my risk of heart disease?

What is the Link Between Fish Oil and Heart Health?

How Can Omega-3 Fatty Acids in Fish Oil Promote Heart Health? Several possibilities have been suggested, which are supported by animal studies. These protections include

  • Stabilization of blood flow in and around the heart
  • Decrease in the level of triglycerides in the blood
  • Lower blood pressure
  • Prevention of blood clots
  • Reduce inflammation.

The research on these topics has not yet been completed.

Many studies, different results

Despite these animal data, human clinical studies have not consistently confirmed the protective benefits of a fish oil supplement.

A meta-analysis published in JAMA Cardiology found no clear benefit for fish oil supplements in preventing heart disease or severe cardiovascular disease (CVD) such as heart attack or stroke in people at increased risk for CVD.

This was followed by the publication of the ASCEND and VITAL studies, both with mixed results. In ASCEND, which examined diabetics without known CHD, fish oil supplements did not significantly reduce heart attacks or strokes, but the risk of death from heart attack and stroke. VITAL investigated the effects of fish oil on primary prevention in people with a regular risk of heart disease and was also unable to detect a significant reduction in all major CVD events. However, there were fewer heart attacks in subjects who took fish oil supplements, especially subjects who did not eat fish.

The REDUCE-IT study was published next. This study looked at the effects of high-dose fish oil supplements on people with high blood triglyceride levels who were at increased risk of CVD. In contrast to previous studies, REDUCE-IT found a significant reduction in cardiovascular events in subjects who took the high-dose 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 used a dose of 4 grams of EPA alone. (Vascepa, a prescription version of the EPA fish oil additive used in REDUCE-IT, is FDA approved for the treatment of very high triglyceride levels of 500 mg / dL or higher. In November, an FDA advisory panel unanimously voted to expand the approval of Vascepa If the FDA follows the advisory panel’s recommendation, Vascepa may be prescribed to reduce the risk of cardiovascular events such as heart attack and stroke. The FDA’s decision is expected in late December.)

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

what does that mean to you?

Omega-3 supplements made from fish oil appear to be heart-healthy and have a protective effect on CHD. Before we all reach for supplements, however, it may be worth following a heart-healthy diet that includes fresh fruits and vegetables and lean proteins like 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-dose EPA fish oil supplements.

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