Omega-3 fatty acid supplements are widely recommended for heart health. But new data suggests that one of two omega-3 fatty acids commonly paired in supplements might actually block the benefits of the other.

Omega-3’s play a key role in many body functions. They’re an essential component of bone health; they can help the body defend against cancer; and may even reduce the symptoms of premenstrual syndrome.

Consumers who are worried about getting the right balance of omega-3s are advised to turn to dietary sources like fatty fish, such as salmon and mackerel, not supplements, as their main source.

The three omega-3 fatty acids may not be equal when it comes to heart health benefits, a recent study found. Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) — alpha-linolenic acid (ALA) is the third — are often found together. DHA is a primary structural component of the human brain, cerebral cortex, skin and retina. EPA is found in the flesh of cold-water fish, including mackerel, herring, tuna, halibut and salmon. It is often prescribed to reduce triglyceride levels. The researchers found that higher levels of DHA appear to worsen health outcomes no matter the level of EPA.

“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,” researcher, Viet Le, of the Intermountain Healthcare Heart Institute in Salt Lake City, said in a statement.

The study involved data on nearly 1000 patients selected from a database that followed 25,000 patients for a decade. People participating in the study had undergone a first round of heart imaging known as cardiac angiography between 1993 and 2012. Their exams also included testing EPA and DHA levels in the blood at the time of imaging. Patients were tracked for the next ten years for major cardiac events like heart attacks and strokes, and their data were analyzed to determine the relationship between DHA and EPA levels on major coronary events.

Patients who had the highest levels of EPA had a statistically reduced risk of cardiac events, while higher levels of DHA compared to EPA actually seemed to blunt the heart healthy effects of EPA, the researchers found.

Because these two omega-3 fatty acids are so often combined in supplements, researchers raised concerns about their continued use since the average consumer is unaware of this adverse interaction, and so many health platforms advocate the use of omega-3 supplements. DHA is also added to some infant formulas and is promoted as a nutrient essential for brain growth. These findings leave its value in this regard open to question.

To better understand the way that EPA and DHA interact and affect one another in the bloodstream, more studies will need to be done. These findings also raise questions about how other common supplements may be interacting and affecting each other’s effectiveness.

Consumers who are worried about getting the right balance of omega-3s are advised to turn to dietary sources like fatty fish, such as salmon and mackerel, not supplements, as their main source. Two servings per week is enough to get the benefits. Otherwise, look for EPA-only omega-3 supplements the next time you purchase vitamins, although these may prove difficult to find!

Speak with your doctor or another trusted healthcare practitioner to decide what, if any, supplements are right for you.

The study was presented virtually on May 17 at the 2021 American College of Cardiology's Scientific Session.