Evidence from innumerable studies attest that people consuming one to two servings of seafood per week are less likely to die of heart disease than those who do not. In particular, oily fish, such as salmon, mackerel and tuna, are a rich source of omega-3 fatty acids that are shown to be beneficial to the heart and help protect against cardiovascular diseases.
But not all omega-3 fatty acids are equal. The three main omega-3 fatty acids are alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is found mainly in plant oils such as flaxseed, soybean, and canola oils. DHA and EPA are found in fish and other seafood.
ALA is an essential fatty acid, which means that your body cannot make it, so you must obtain it from the foods and drinks you consume. Your body can convert some ALA into EPA and then to DHA, but only in very small amounts. Therefore, getting EPA and DHA from foods,(and dietary supplements if you take them, is the only practical way to increase levels of these omega-3 fatty acids in your body.
Many people take supplements that contain omega-3 fatty acids in the belief that these will also help protect them against cardiovascular disease. The combination of EPA and DHA that are often found in omega-3 supplements, may void the benefits that patients and their doctors hope to achieve, says a new study.
Earlier research had suggested that only high doses of EPA appear to reduce the risk of major adverse cardiovascular events, However, a recently published clinical trial has found no reduction in risk for people with high cardiovascular risk who took a supplement that contained a combination of EPA and DHA.
The new study conducted by researchers at the University of Utah in the United States found that although high levels of EPA in the blood were associated with a reduced risk of major cardiac events and death, rising levels of DHA appeared to negate these benefits.
For their study, the researchers drew on studies of 35,000 blood samples from nearly 25,000 patients and their medical records. They then randomly selected 987 individuals who had received a first heart scan between 1994 and 2012 and quantified their plasma levels of EPA and DHA. At the time of their scan, 41 percent had obesity, and 42 percent had severe coronary artery disease.
Over the next 10 years, 31.5 percent 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. While those with more DHA than EPA in their blood had an increased risk of heart problems compared with those with higher levels of EPA.