Fish, fish oil, and cholesterol

In recent years, many people have taken fish oil capsules to reduce their risk of coronary artery disease (CAD), stroke, and rheumatoid arthritis (RA). Fish oil lowers triglycerides but does not help lower cholesterol. But for people who have had a recent heart attack, a small amount of fish oil capsules may reduce the risk of death from CAD.1

Some people with high triglycerides may take a prescription omega-3 fatty acids medicine (such as Lovaza). This medicine is a highly concentrated form of omega-3 fatty acids, which are found in fish oil. This medicine is used along with diet and lifestyle changes for high triglycerides. This medicine may raise LDL cholesterol levels slightly. So if you take Lovaza, your doctor may closely watch your cholesterol levels.

Fish oil capsules that you can buy without a prescription can have significant side effects. Because of these side effects, most doctors recommend eating 2 or 3 servings of fish a week rather than taking fish oil capsules. The side effects of fish oil capsules include:

  • Large amounts of omega-3 fatty acids (the main type of fatty acid in fish oil) can greatly reduce the ability of the blood to clot normally.
  • Fish oil can cause nausea, diarrhea, belching, and a fishy taste in the mouth.
  • Taking large amounts of fish oil greatly increases the number of calories in the diet. Some suggested doses add more than 200 calories a day.
  • Some studies suggest that taking large doses of fish oil can actually harm your immune system.

Citations

  1. Marchioli R, et al. (2002). Early protection against sudden death by n-3 polyunsaturated fatty acids after myocardial infarction. Circulation, 105(16): 1897–1903.

Last Updated: July 11, 2008

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