Omega-3 from fish contains both eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The study by scientists from Intermountain Healthcare’s Heart Institute in Salt Lake City, Utah, followed research elsewhere suggesting that only high doses of EPA appear to reduce the risk of major adverse cardiovascular events, including heart attack, stroke, and heart failure.
A recently published clinical trial found no reduction in risk for people with high cardiovascular risk who took a supplement that contained a combination of EPA and DHA.
987 patient blood samples
The Heart Institute researchers drew on Intermountain Healthcare’s INSPIRE registry, which includes about 35,000 blood samples from nearly 25,000 patients and their medical records, reports Medical News Today.
They randomly selected 987 individuals who had received a first heart scan at Intermountain Healthcare between 1994 and 2012 and quantified their plasma levels of EPA and DHA.
The average age of those included was 61.5 years. At the time of their scan, 41% had obesity, and 42% had severe coronary artery disease.
Over the next 10 years, 31.5% of all the patients had a major adverse cardiovascular event, which the team defined as all-cause death, heart attack, stroke, or heart failure.
The researchers discovered that people with the highest levels of EPA in their blood at the time of their first scan were less likely to experience a major cardiovascular event.
However, rising levels of DHA appeared to blunt the beneficial effects of EPA.
Those with more DHA than EPA in their blood had an increased risk of heart problems compared with those with higher levels of EPA.
These associations remained after accounting for pre-existing illnesses, namely severe coronary artery disease, chronic obstructive pulmonary disease (COPD), and heart failure.
‘Eat omega-3 rich foods’
“Based on these and other findings, we can still tell our patients to eat omega-3 rich foods, but we should not be recommending them in pill form as supplements or even as combined (EPA + DHA) prescription products,” said lead researcher Viet T Le, a cardiovascular physician assistant at the Institute.
“Our findings show that not all omega-3s are alike and that EPA and DHA combined together, as they often are in supplements, may void the benefits that patients and their doctors hope to achieve.”
Le’s team has submitted the study for publication.
The researcher pointed out to Medical News Today that two randomised clinical trials have found heart benefits for EPA-only supplements, whereas four have shown no benefits from combinations of EPA and DHA.
He noted that these trials involved pharmacy-grade supplements, whereas “off-the-shelf” omega-3 products are unlikely to meet such high standards of purity. In addition, commercial supplements do not give consumers the option of taking EPA without DHA.
Le conceded that the relative levels of omega-3s that his team found in the participants’ blood could reflect some other dietary or physiological factor (a “confounder”) that also influenced their heart health risks.
“Yes, that is always possible,” Le said. “This is a prospective analysis of retrospective data and, thus, confounding can occur.”
Dr Andrea Wong, a senior vice president for scientific and regulatory affairs at the Council for Responsible Nutrition (CRN) - a trade association that represents the supplement industry – told Medical News Today that “a large body of evidence” supports the benefits of both EPA and DHA for heart health.
She cited a recent analysis that pooled data from 17 studies and found that higher circulating levels of EPA and DHA, both separately and together, were associated with a lower risk of premature death and death from cardiovascular disease.
Wong told the website: “Supplementing with EPA and DHA omega-3 fatty acids can contribute to heart health, but as one of many healthy habits to maintain a healthy heart. CRN recommends consumers at high risk or those with a history of cardiovascular disease talk with their cardiologist about what supplements are right for them.”