A recent widespread study has rekindled the debate over whether omega-3 supplements reduce the risk of heart attack and stroke. The study showed that a certain form of omega-3 oil reduced the risk of people with heart disease suffering from a major “endpoint event” by 25 percent.
This endpoint is part of a combination of several serious problems such as fatal or non-fatal heart attack, stroke, angina (chest pain), and coronary surgery.
The REDUCE-IT study, enrolling more than 8,000 participants, was presented at the American Heart Association’s scientific sessions in Chicago and published in the New England Journal of Medicine.
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It was the largest randomized controlled trial to date (in which one group receives the tested intervention and another receives a placebo and the results are compared) to test the benefits of omega-3 supplements in heart disease.
However, before you buy fish oil supplements from your local pharmacy, there are a few things to consider. The drug Vascepa tested was not a normal, over-the-counter fish oil capsule.
Vascepa is made from a highly refined component of fish oils (icosapent ethyl) and participants were given a very high dose (4 grams per day). This is far more omega-3 than most people ingested with fish oil capsules.
Vascepa requires a prescription in the US, but not everywhere and not in Australia.
Study participants either had cardiovascular disease and were over 45 years old or were at high risk for cardiovascular disease and were over 50 years old. The people at risk had diabetes and at least one other risk factor. The results apply best to people with similar characteristics as the study group and cannot necessarily be generalized more generally.
Even so, it was a pretty good study conducted by reputable investigators in 11 countries with convincing results. What does this mean for advice on whether or not to take fish oil supplements to avoid serious heart problems?
Not everyone with heart disease would necessarily benefit from the supplements that the study participants received. from shutterstock.com.
A bit of history
In the early 2000s, medical authorities recommended a fish oil supplement for people who had a cardiovascular event such as a heart attack or stroke.
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At the time, two large randomized controlled trials reported that eicosapentaenoic acid supplements – containing EPA and docosahexaenoic acid (DHA) – significantly reduced fatal heart disease. EPA and DHA are the main oils in fish oil supplements and are known as omega-3 fatty acids.
In 2017, the American Heart Association was more prudent, finding that the dramatic benefits previously seen were less apparent in subsequent studies. However, dietary supplements were still recommended for certain people with heart or vascular disease.
The tide seemed to have completely turned in early 2018 when a widespread study concluded that there was little evidence of the benefits of fish oil supplements in preventing heart disease. The study was a systematic review that combined the results of ten studies of fish oil supplements (at a lower dose than the REDUCE-IT study) that included 77,917 older adults at high risk for cardiovascular disease.
So what are we supposed to believe? A well-conducted randomized controlled trial or a systematic review of all evidence? An RCT is considered the gold standard by policy committees. A well-conducted systematic review or meta-analysis is also considered meaningful.
What’s the verdict?
Omega-3 fatty acids, including over-the-counter capsules, have certain biological effects. (
Flickr: Jo Christian Oterhals (CC-BY-NC-ND-2.0)
The studies in the systematic review differed greatly in design, dose, patient population, endpoints, and the validity of the merger of all studies is questionable. Finding no evidence of benefit is also not the same as finding no benefit, especially for some people under certain conditions that can be lost in the overall analysis. In addition, the results not only reflect the treatment studied, but also the quality of the studies included.
REDUCE-IT was financed by the manufacturer. There is no other way this could have been done and if the results are correct millions of lives could be saved, but some will question the veracity of the results due to the source of funding. All of this leaves you feeling certain that heart health supplements are good in the air.
Fortunately (and as far as we know) there are some “truths” left. Eating fish is still good for you. The origin of the fish is important not only to avoid contaminants, but also because the omega-3 content and relative amounts of EPA and DHA vary. Cold water, oily fish like salmon, sardines, mackerel, trout and tuna contain the most.
If you can’t eat fish, there are plant sources of omega-3 fatty acids in some nuts and vegetable oils like canola, chia, flaxseed, and soy. These have not been studied as extensively as those of marine origin.
Omega-3 fatty acids, including over-the-counter capsules, have certain biological effects. They reduce triglycerides (the type of fat that helps harden the arteries) and the risk of blood clots, and are anti-inflammatory. These changes usually occur with higher doses.
The evidence will continue to evolve, but in the meantime, and based on a recent evidence review, the National Heart Foundation recommendations do not advise health professionals to routinely recommend omega-3 supplements for heart health. It is recommended that health professionals consider using omega-3 supplements for those with high triglyceride levels and as an additional treatment for heart failure.
Finally, everyone should include two to three servings of fish per week in their diet.
Garry Jennings is Professor of Medicine at the University of Sydney. This article first appeared on The Conversation.