Millions of Americans take fish oil supplements and believe that substances' omega-3 fatty acids will give them a edge over heart disease. What most consumers do not know, however, is that the link between fish oil and heart health has never definitively been proven. As Slate reports, the original study purporting this connection was based on questionable data, and no researchers have been able to establish a doubt-proof connection since.
The fish oil story begins back in the 1970s, when two Danish researchers working in the Arctic noticed that Inuit rarely died from heart attacks. The "Eskimo diet," which is rich in fish, must protect them from heart disease, they concluded. As Slate reports, however, there was one glaring problem: "the two Danes never proved that the Inuit had low rates of heart disease."
The researchers, both clinical chemists, studied blood samples from 130 Inuit and observed what their subjects ate. To calculate rates of heart disease, Slate reports, they relied on death certificates and hospital records from Greenland.Although the Inuit mostly dined on meat from fish, birds, seals and whales, the researchers found that very few of them died of heart attacks or were admitted to the hospital because of heart problems. Their omega-3 fatty acid rich diets, the researchers concluded, must be helping them.
Slate explains why making that leap is problematic:
But there’s a problem with relying on official medical records in a part of the world so remote that—according to a deputy chief medical officer in the 1970s—30 percent of people lived in settlements with no medical officer at all. This meant many death certificates were filled out by whoever was nearby, without a doctor ever seeing the body. Someone experiencing heart attack symptoms might not be close enough to a hospital to attempt a trip. Even if he did, the hospital might have limited equipment for diagnosis. And 20 percent of heart attacks cause sudden death.
Experts today have warned that the original study likely strong underestimated the number of Inuit who succumbed to heart disease. Nevertheless, Slate continues, studies that have come in years since often cite that original paper without questioning its premise. In the cases that researchers have conducted trials on fish oil and its possible link to heart health, results have been inconclusive or mixed. As Slate writes, "To truly learn whether omega-3s guard heart health or not, we need research that goes a step further: large-scale, randomized trials."
Now, such a trial is underway. Around 25,000 people are taking fish oil supplements or a placebo for five years. In 2018, researchers will analyze the results and see if those who took the fish oil had any kind of healthy edge over the control group.
In the meantime, however, Americans will likely continue to drop $15 billion per year on fish oil supplements harvested from small fish such as herring and anchovy—species that suffer from overfishing.