Omega-3s Aren’t That Good for Your Heart After All

Omega-3s were supposed to protect us all from heart disease and other health problems, but it took a while for the evidence to calm the hype around these supplements. Based on a large and important study published earlier this year in JAMA Cardiology , there is evidence that fish oil or omega-3 supplements will not help people with heart disease.

What about all the other reasons you might be taking omega-3s? Bad news: Major reviews have concluded that there is little evidence that omega-3s are beneficial for dementia , depression , inflammatory bowel disease, or age-related macular degeneration , all of which were considered potential benefits of supplementation at some point. There is also little evidence that taking omega-3s or DHA during pregnancy will make your baby smarter or prevent allergies . Some studies show that taking omega-3s can reduce the risk of breast cancer , but others show an increased risk of prostate cancer . There are a few glimpses of hope; Omega-3s may help reduce joint swelling and pain in people with rheumatoid arthritis , and may also help some people with dry eyes , although more research is needed for these conditions. Other research on omega-3s is ongoing, including the large clinical trial VITAL , which tests omega-3 and vitamin D supplements in more than 25,000 healthy adults to see if they affect cancer, heart disease and stroke.

Among US adults, 12% reported taking fish oil supplements in 2012, up from 1.3% in 1999. A 2017 study found that 22% of US adults over 60 were taking omega-3s, making it the third most popular supplement at this age. group, after multivitamins and vitamin D.

So why have we been told over the years to take omega-3 or fish oil supplements? This story begins with the Inuit in Greenland – more precisely, with what European researchers observed them.

How Omega-3s Became Known

In the 1970s, two Danish doctors, Hans Olaf Bang and Jorn Derberg, learned that Greenlanders had a very low prevalence of coronary heart disease. This type of cardiovascular disease is usually caused by deposits of cholesterol that constrict the main arteries of the heart, which can eventually cause a heart attack if the arteries are blocked. Intrigued, Bang and Derberg set out to research the Inuit diet in Greenland to see if it had any secret to their health.

Theyfound that Greenlanders ate largely the opposite of the low-fat diet recommended for cardiovascular health in the Western world, but they had lower plasma triglyceride levels than Danish control subjects. Their diet was low in fruits and vegetables and high in animal fats, mainly from seal and whale oil. This fat was rich in omega-3 fatty acids produced by marine phytoplankton and passed down the food chain to fish, seals and whales in the Inuit diet. Bang and Derberg have highlighted these fats as the key to heart health in Inuit.

When we eat omega-3 fatty acids, they are incorporated into cell membranes and serve as precursors for eicosanoids, a diverse family of cellular signaling molecules that perform important functions such as regulating inflammation, blood clotting, and blood pressure. Studies in rodents and petri dishes, as well as short-term studies in humans, have shown that omega-3s help prevent heart rhythm disturbances and blood clots, reduce inflammation, and lower blood triglyceride levels.

Researchers from around the world have begun testing the link between omega-3s and heart disease and other health conditions. And supplement makers, who usually don’t wait for major clinical trials before shipping their products to market, have begun siphoning fish oil capsules, happy to spread the benefits of bulk fish.

Something smells like fish

But a closer look at the origins of the fish oil story shows that more skepticism was justified from the start. According to a 2014 article in the Canadian Journal of Cardiology , Bang and Derberg’s hypothesis was based on thin ice. First, they never measured the incidence of cardiovascular disease in Greenland, relying instead on sketchy local estimates that were unreliable as many people lived too far from medical facilities for their illnesses or causes of death to be accurately diagnosed. Subsequent studies have shown that the incidence of cardiovascular disease in Inuit populations is as high , if not higher than in Western populations, despite the high intake of omega-3 fatty acids.

Plus, Greenlanders seem to have developed genetic differences that allow them to adhere to their unique diet. A 2015 article in Science identified gene variants common in Inuit (and rare in Europeans) that help them metabolize fatty foods and keep blood omega-3s in balance with other body fats. Without this genetic background, someone of European descent following an Inuit diet could have much higher levels of cholesterol and omega-3s in their blood.

But fish is still good for us. Observational studies that assess how much fish people eat and the incidence of fish consistently show that eating fish at least once a week is associated with a lower risk of death from coronary heart disease.

But these studies can only show a correlation, not a direct causal relationship, between eating fish and improving heart health, and they cannot tell us if omega-3 capsules have the same effect as fish in the diet. Maybe fish is good for us because it contains not only omega-3s, but also other nutrients such as vitamin D, iodine, selenium, and protein. If you eat salmon fillets instead of steak, you also consume a lot more polyunsaturated and less saturated fat.

The truth comes out

To find out if omega-3 supplements actually improve our heart health, we needed a clinical trial. Many such studies have been conducted over the past several decades, and the best of them have been summarized in the recent JAMA Cardiology Study . As part of a meta-analysis, the study pooled the results of 10 randomized trials, involving a total of about 78,000 people at high risk for cardiovascular disease. Some of the participants took omega-3 supplements and some did not. On average, the studies tracked people for about four and a half years and together recorded 6,273 cardiovascular events, including heart attacks, strokes, and procedures such as coronary artery bypass grafting and angioplasty. Several of the 10 trials found benefits of omega-3s, but when they were all combined, more data showed no reduction in cardiovascular events in people taking the supplements.

Another major study published by the US Department of Health and Human Services Agency for Medical Research and Quality in 2016 came to the same conclusion.

Bottom line: take fish oil if you really want to, but don’t expect much

The American Heart Association says that despite mixed evidence, it is still prudent to take an omega-3 supplement if you have recently had coronary artery disease, such as a heart attack, or if you have heart failure but there is no evidence that should be used in the general population. There is also a small risk (beyond cost) of taking omega-3s in commonly used doses, usually containing about one gram of fish oil.

The authors of the recent study also note that early research on fish oil and heart disease did show benefits, and the disappointing results from more recent studies may be linked to changes in diet and medicine over time. For example, omega-3 supplements can only benefit heart health if you are indeed omega-3 deficient, and since early research was highlighted in the media, more people started eating fish, so the supplement did not provide any additional benefits. benefits. Or maybe, as we got better at managing heart disease with drugs like statins, the benefits of omega-3s were no longer apparent.

More than 40 years have passed since Bang and Derberg visited Greenland and published their theory about fish oil and omega-3s, and there are many lessons to be learned from their history. First, it is easy to mislead the assumption that the correlation between two variables is analogous to causation. Nutrition (and life in general) is almost always more difficult. Second, science is an ongoing process, and it can take decades and many, many studies to answer a simple question. Third, supplementation is almost always exaggerated, while evidence for dietary diversity, including fish, is only increasing.