Fish Oil Increases Risk of Stroke & Heart Disease
In the 1970s, Danish scientists, Dr. Dyerberg and Professor Bang, who were studying the Inuit in Greenland discovered something intriguing - despite a diet high in fat, the Inuit had a remarkably low incidence of cardiovascular disease. This remarkable finding flew in the face of the prevailing medical dogma that preached that such diseases were caused by a high fat diet. Further research found that this was because the Inuits diet of fatty fish contained high levels of omega-3 fatty acids. More research confirmed that diets high in omega-3 fatty acids (specifically EPA and DHA) have many important health benefits, including regulating inflammation and blood lipids and promoting brain and cardiovascular health.
This has led to a huge market for fish oil supplements. Fish oil is one of the top-selling supplements in the US and Western countries. In fact, one in five older adults in the US takes a fish oil supplement for heart health, according to one study. While there is good evidence that a diet high in omega-3 fatty acids is great for health, there is little scientific evidence that fish oil supplements do much for our health. In fact, many studies show that fish oil supplements don’t do anything for cardiovascular health.
A recent study from the British Medical Journal has shown that fish oil supplements may actually increase the risk of atrial fibrillation and stroke. This study involved almost 500,000 participants; it included healthy people, those with atrial fibrillation, and those with major cardiovascular disease. Shockingly, regular use of fish oil in healthy people increased the risk of developing atrial fibrillation and stroke. People with atrial fibrillation and cardiovascular disease, fish oil supplements conferred a small protective benefit from progressing to major cardiovascular problems and death.
Why the difference between fish oil supplements and a diet high in fish oil? A lot of this disparity is due to differences in purity and consistency in those supplements. The study from JAMA Cardiology showed a lot of variation in the doses of EPA and DHA in these supplements. Furthermore, the extraction processes from marine sources varies among manufacturers; some utilize chemicals that damage or alter the chemical composition of the fish oil while others may introduce toxic contaminants. Some supplements contain heavy metals like mercury or other pollutants found in the ocean. Finally, fish oil may oxidize and turn rancid once extracted and stored as a supplement.
So, what should we do? I think if you are a healthy person without pre-existing heart disease, it would be best to increase you consumption of fatty fish (e.g., mackerel, cod, salmon) instead of using fish oil supplements. If you have pre-existing heart disease, you may have some benefit from fish oil supplements (of course, consult your cardiologist first) but you should look for supplements made by manufacturers with high standards of purity and potency.
