In Europe, fish oil pills must now list that atrial fibrillation is a common side effect, according to the Pharmacovigilance Risk Assessment Committee of the European Medicines Agency (Medscape, October 13, 2023). Fish oil pills are also called omega-3 supplements and they may be recommended to treat high blood triglyceride levels if lifestyle changes fail to lower triglycerides to normal (J Clin Invest, Mar 15, 2021;131(6): e147558). High triglycerides are a significant risk factor for diabetes and heart attacks (Cardiovascular Diabetology, July 26, 2023;22(187)).

Doctors often recommend fish oil pills to treat high triglycerides and to help prevent heart attacks. However, a fish oil dose of more than one gram per day has been associated with increased atrial fibrillation risk (Circulation, Dec 21, 2021;144(25):1981-1990; Curr Atheroscler Rep, 2020 Jul 16;22(9):45), and doses as high as of four grams per day markedly increased risk for atrial fibrillation. The higher the dose of fish oil pills, the more likely a person is to suffer atrial fibrillation. Fish oil pills were found to increase risk for atrial fibrillation by 37 percent in patients who had heart disease (Eur Heart J Cardiovasc Pharmacother, July 23, 2021;7(4):e69-e70), but other studies failed to show an association of fish oil pills with increased risk for atrial fibrillation (JAMA, Mar 16, 2021;325(11):1061-1073).

High Triglycerides, Diabetes and Heart Attacks
When blood sugar levels rise too high, the liver coverts the extra sugar to triglycerides. Having triglycerides greater than 150 mg/dL is associated with high blood sugar levels after eating, which puts a person at high risk for both diabetes and heart attacks. Doctors often treat people with high triglyceride levels with fish oil pills that have been shown in some studies, but not all, to lower high triglycerides. However, most people can lower high blood triglycerides by following the lifestyle rules to control high blood sugar levels:
• exercise
• lose excess weight
• eat lots of vegetables, whole grains, beans, seeds and nuts
• avoid sugar-added foods and all drinks with sugar including fruit juices
• restrict or avoid mammal meat, fried foods and most refined carbohydrates and processed foods
• avoid smoke and alcohol.

Omega-3’s from Fish and Plants May Help to Prevent Heart Attacks
People who had higher blood levels of omega-3 fatty acids at the time of a heart attack were far less likely to die or to have repeat heart attacks within three years, compared to those who had lower levels (J Am Coll Cardiol, Nov, 2020;76(18):2089-2097). The sources of omega-3s in the 944 heart attack patients in this study included both fish and plants.

Omega-3 fatty acids can help to lower high triglycerides, which may help to prevent heart muscle damage before and during a heart attack (Circulation, Aug 2, 2016;134(5):378–391). People whose diet included deep-water fish were at a reduced risk for suffering and dying from a heart attack (Circulation, 2018;138:e35-e47).

Get Your Omega-3s from Foods
I believe that you should be able to get enough omega-3s from eating oily fish (such as salmon or sardines) and a wide variety of plants. Some foods are marketed as particularly rich sources of omega-3s — flaxseeds, chia seeds, hemp seeds, soybeans, seaweed, algae, perilla oil and so forth — but you can get plenty of omega-3s in your regular diet if you eat lots of ordinary vegetables, nuts, beans and other seeds. Omega-3 fatty acids are classified into short chain fatty acids found in plants and long chain fatty acids found in fish. The health-promoting benefits of omega-3s come primarily from the long chain omega-3s, but some of the short chain omega-3s in plants can be converted to long chain omega-3s, so you can get the heart attack preventing benefits with a healthful plant-based diet (J Am Coll Cardiol, 2020;76(18):2098-2101).

My Recommendations
The evidence that eating fish twice a week helps to prevent heart attacks is strong so I do that and recommend it to others. However, if you don’t like fish and want to take omega-3 pills instead, test them for rancidity by breaking open a capsule from each bottle you purchase. If they smell fishy, throw the whole bottle out, since rancid oils increase risk for heart attacks and certain cancers.

If you eat no seafood or other animal products, be sure to eat a wide variety of plants and include lots of seeds (beans, nuts, whole grains, seed oils and so forth). Also take vitamin B12 pills to prevent nerve damage caused by lack of that vitamin. If you have high blood triglyceride levels, talk to your doctor about the lifestyle factors that lower triglycerides listed above.