A rather damning finding, and it was based on one of the largest studies to date examining the effects of omega-3 intake and future health outcomes. It looks like one of the most widely recommended dietary options for preventing (heart) disease is actually causing it. Unfortunately, the study did not look at omega-6 consumption in the same context, but considering the omega-6 is even more inflammatory than omega-3, the findings about omega-6 would have probably been even more damning, especially considering that omega-6 intake dwarfs omega-3 intake in most Western countries. Now, the study did find that in people with already established CVD, omega-3 intake lowered the risk of future cardiac/brain ischemic event or dying from one. However, I suspect that these findings are due to the fact that people with established CVD already have very high omega-6 intake (which is what caused their CVD) and the addition of omega-3 dampened a bit the inflammatory state. However, since the study did not control for omega-6 or SFA intake we do not know what the lowest baseline rate of CVD or ischemic events could have been. In other words, if people with SFA intake had the lowest CVD and ischemic rates, compared to the omega-6 and omega-3 groups, then omega-3 intake lowering the ischemic rates below the omega-6 group but keeping them above the SFA group would still very much mean that omega-3 is a net negative on people with already established CVD. The study does hint that this may be the case (see quote from the study below). In that case, the recommendations should not be to replace omega-6 with omega-3 (which is what medicine currently recommends), but to replace all PUFA with SFA, as much as possible.
https://bmjmedicine.bmj.com/content/3/1/e000451
“…Higher doses of omega 3 fatty acids used in previous studies might have had an important role in causing an adverse effect on atrial fibrillation.21 One study found that high concentrations of fish oil altered cell membrane properties and inhibited Na-K-ATPase pump activity, whereas a low concentration of fish oil minimised peroxidation potential and optimised activity.23 In another study, individuals with atrial fibrillation or flutter had higher percentages of total polyunsaturated fatty acids, and n-3 and n-6 polyunsaturated fatty acids, on red blood cell membranes than healthy controls.2”
https://www.healthline.com/health-news/fish-oil-heart-disease-stroke-risk
“…Fish oil derived from fatty fish like salmon, mackerel, and trout is often recommended for its anti-inflammatory effects, especially in people with cardiovascular disease (CVD), high blood pressure, abnormal lipids, and rheumatoid arthritis. Fatty fish are a great source of two omega-3 fatty acids that the human body needs but cannot make for itself: docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). However, while it might seem like a good idea for healthy people to also supplement with fish oil to help prevent disease, the results of a large, long-term study published on May 21, 2024, in the journal BMJ Medicine, indicate that this may not be the case. The researchers found that using fish oil on a regular basis might actually increase the risk for healthy people to go on and develop first-time heart disease and stroke.”
