80 years ago, British researchers studying the Inuits of Greenland found that despite having diets that were extremely high in protein—with much of their food being sourced from the seals, fish, and other sea life they hunted and caught—there was “no evidence that the high-protein diet cause[d] any ill-health.” In fact, repeated studies found, “an almost total absence of cardiovascular-renal diseases in the population.”

It was this seemingly contradictory observation that led generations of researchers down the path towards delineating the relationship between omega-3 fatty acids, particularly DHA and EPA, and potential benefits to heart health. Hundreds of studies on the subject have been conducted, many of them finding a correlation between high levels of DHA and EPA in the diet and better baseline heart health—such as reduced blood pressure and heart rate—as well as reduced incidence of diseases relating to poor heart health.

However, there are still many questions as to what these benefits are, and what the mechanisms are by which omega-3s appear to support healthy cardiovascular function. This article gives a brief overview of recent research into omega-3 fatty acids and whether they contribute to heart health, and if so, how.

Many studies have found strong correlations between blood levels of DHA and relative risk of dying from cardiovascular disease. However, some studies have had ambiguous results.

An analysis of more than 160,000 people published in 2024 by the Mayo Clinic Proceedings journal found that the 1/5th of people who had the highest blood levels of the omega-3 DHA, compared to the 1/5th with the lowest levels, had a lower risk of dying from a variety of causes over a roughly 14-year study period. The largest decline in mortality risk was for deaths resulting from cardiovascular disease. Those with the highest DHA levels were 21% less likely to die from heart disease.

A smaller American study of 2,700 American participants conducted in the early 2010s had similar results. High levels of DHA were associated with a 20% lower risk of death, and high levels of omega-3s were associated with a 27% lower mortality risk. According to the study authors, “Lower risk was largely attributable to fewer cardiovascular than noncardiovascular deaths.” When comparing years lived after the age of 65, those with the highest levels of omega-3s lived 2.2 more years than those with the lowest levels. Meanwhile, a study of 2,500 participants in the Framingham Heart Study found that those with the highest blood levels of omega-3s had a 39% lower likelihood of suffering from cardiovascular disease.

The potential benefit of omega-3s does vary from study to study. For instance, a 2017 study found only a relatively modest 8% reduction in the likelihood of cardiac death in those who took DHA and EPA. Perhaps that analysis did note that those who took more than 1 gram per day of combined DHA and EPA had a 29% lower likelihood of cardiac-related death. Given the variability between studies, as well as the publication of studies which have found no cardiovascular benefits from omega-3s, researchers are starting to pay more attention to how much DHA and EPA people are taking, and how that correlates with heart health outcomes.

Studies have begun to find correlations between omega-3 doses and reduced risk of cardiovascular disease and cardiac death—the more omega-3s, the better.

A 2020 study, “Effect of Omega-3 Dosage on Cardiovascular Outcomes: An Updated Meta-Analysis and Meta-Regression of Interventional Trials,” looked for relationships between the dosages of DHA and EPA that people took and their risk of negative health conditions.

Based on data from 40 clinical trials with more than 135,000 participants, the analysis found that DHA and EPA intake were associated with a:

• 35% reduced risk of fatal heart attack
• 13% reduced risk of heart attack
• 10% reduced risk of coronary heart disease
• 9% reduced risk of fatal coronary heart disease

The analysis was then taken a step further, with daily dosages ranging from 400 mg to 5.5 grams of DHA and EPA being correlated against likelihood of negative cardiovascular events. It was found that for each additional gram taken per day, the risk of cardiovascular disease events (heart attack, angina, stroke, heart failure, peripheral arterial disease, sudden death, and non-scheduled cardiovascular surgical interventions) was reduced by 5.8%, and the risk of heart attack was reduced by 9.0%. The potential heart health benefit of omega-3s appeared to stack—the more taken by study participants, the better.

The study’s authors were careful to look for other variables that could account for the results, including whether the studies used DHA and EPA or EPA only, how variations in participants’ baseline risk of heart conditions affected outcomes, and when the studies were published. The study authors found no indication that supplementation of a single omega-3 correlated with better outcomes, versus taking DHA and EPA. They did not find evidence that EPA alone was more or less effective than DHA plus EPA, and that the years of publication did not correlate with the magnitudes of the effects measured.

How DHA and EPA potentially support heart health appears to be multi-factor in nature—that is, they may modestly benefit multiple biological functions, with these resulting in a sizeable overall benefit.

In the 2024 Mayo Clinic Proceedings omega-3 analysis, the authors offered several rationales for why DHA may benefit heart health and reduce the incidence of cardiac death (all specifics directly sourced from the study):

• Blood pressure and heart rate reduction: Lower blood pressure and resting heart rates are associated with reduced risk of cardiovascular disease and premature death. Studies cited by the authors found that 3 grams of combined DHA and EPA per day lower systolic blood pressure by about 4.5 mm Hg in those with high blood pressure, and 2 mm Hg in people with normal blood pressure, and decreases resting heart rate by about 5 beats per minute. Even modest improvements can have significant impacts on heart health. A 2015 analysis published in The Lancet found that for every 10mm Hg reduction in systolic blood pressure, the risk of various heart conditions was reduced by roughly 15% to 30%.
• Vagal tone improvement: People with higher vagal tone—a measure of the vagus nerve’s activity, which regulates a variety of cardiac functions—tend to have a lower risk of cardiovascular and overall mortality. Studies cited by the authors indicated that DHA and EPA supplementation have been shown to improve vagal tone.
• Reduction in rate of telomere shortening: Per the authors, telomere shortening at advanced rates is associated with cardiovascular disease and other age-related disorders. Blood levels of DHA and EPA have been shown to predict the rate at which telomeres shorten, and DHA and EPA have been shown to lengthen telomeres.

Identifying the potential benefit of omega-3s for heart health likely requires an accounting of the dosage, as well as the population being studied and the types of heart conditions in question.

A 2024 review of various studies that attempted to make sense of sometimes contradictory and confusing research, “Omega-3 fatty acids in primary and secondary prevention of cardiovascular diseases,” identified several factors that could be in play:

• Variability of dosing of DHA and EPA, and ratio of DHA versus EPA in each studied supplement, as noted above.
• Differences in baseline diets in different populations—studies of Italian and Japanese populations, which tend to consume more fish and have higher omega-3 levels, have found weaker or no benefits from omega-3 supplementation.
• Type of cardiac outcome being studied—reductions in the risk of fatal heart attacks and fatal coronary heart disease events tend to plateau quickly as dosage increases, while reductions in the risk of nonfatal heart attacks and other heart events tend to continue to scale with larger dosages of DHA and EPA.
• Differences in dosing versus actual blood levels—individuals can be more or less responsive to DHA and EPA supplementation, and some people may require higher dosages to achieve an omega-3 index that delivers a meaningful benefit.

Other studies have hinted at just how complex the relationship between omega-3s and heart health may be. A 2024 analysis, “Fish and Omega-3 Fatty Acids: Sex and Racial Differences in Cardiovascular Outcomes and Cognitive Function,” reviewed data from 24 studies comprising more than 700,000 participants, looking for differences in outcome correlating with gender and/or race. A few highlights:

• In one American study of nearly 26,000 people, men had a 28% lower risk of suffering a heart attack when supplemented with 860 mg of DHA and EPA. Women didn’t show such a statistically significant reduction.
• In the same study, African-American participants had a 77% reduction in the risk of heart attacks, while people of other races derived no benefit.
• In a Chinese study, Asian women in the top 1/5^th of fish consumption had a 22% lower risk of cardiovascular disease death versus those in the bottom 1/5th, while Asian men showed no such benefit.
• In the American Multi-Ethnic Study of Atherosclerosis, after 10 years, men with the highest blood levels of EPA had an atherosclerosis risk reduction of 42%, while women had a risk reduction of 61%.

As the above should make obvious, there is a tremendous amount of variation in the results of research into associations between omega-3s and heart health. These may be based on dosage, diet versus supplementation, use of DHA and EPA versus DHA versus EPA, the national and racial backgrounds of those being studied, statistical noise, and other variables which have not yet been identified. Given the many variables at play, and the still preliminary nature of much of the omega-3 research being conducted, you should consult with a health or medical professional before trying an omega-3 supplement for heart health reasons.

This article is intended solely as an overview of research on the potential benefits of omega-3s for heart health, and health claims about DHA and EPA are narrowly delimited by the FDA.

While it is recognized that omega-3 fatty acids are essential nutrients and benefit human health, they are not indicated as a treatment for any heart disease or disorder. This article is intended solely as an overview of research on the potential benefits of omega-3s for heart health. As of 2024, the U.S. Food & Drug Administration does not object to certain qualified health claims (QHCs) about the use of DHA and EPA. For more information, please refer to the FDA’s websites for the QHCs they announced in 2004 (see here and here) and 2019.