Omega 3's (Fish Oil and Flax Seed Oil) who should take them?

It seems like everyone is taking Omega 3 tablets these days doesn't it? Fish Oil capsules and Flax seed oil supplements containing Omega 3's are advertised and sold in every health food store and pharmacy. Common wisdom is that these supplements are good for everything from preventing heart disease to lubricating joints.

Omega 3's became popular when studies showed that people who ate more fish seemed to have lower rates of cardiovascular disease. Scientists knew that some types of fish were high in Omega 3 fatty acids. Because they have some anti-inflammatory effects it was thought that the Omega 3's might explain the link between higher fish intake and lower rates of cardiovascular disease. Omega 3 supplements were also found to lower triglycerides and since high triglycerides ( a type of bad cholesterol) are associated with an increased risk of heart disease this theory was attractive.
There were a few weak points in the theory though. First, the original studies were not randomized controlled trials. They were population studies. That means they looked at diet and diseases in one group of people like Eskimos or Swedes and compared them to another group of people like Americans or Australians.  Its possible though that there may have been other lifestyle or genetic differences between the two groups aside from their fish consumption that could explain the difference in heart disease. Additionally, the people who ate a lot of fish may have had lower rates of heart disease not because they were eating more fish but because people who eat more fish tend to eat less red meat. Another weakness in the theory is that fish are not a bag of Omega 3 fatty acids. They are complex foods made of various proteins, carbohydrates, fats and many other minor components. Its possible that even if a link exists it may be something other than the Omega 3's in the fish that are causing this effect.

Over the past 3 decades many studies have been done to try and sort out the possible link between Omega 3 fatty acids and heart disease as well as other illnesses like arthritis, depression, and cancer. Because of all the issues described above, when randomized controlled trials are done the benefits seen in the original population studies are often not seen in the controlled trials and most of the hoped for benefits of Omega 3's have not been found when high quality studies were done to look at these issues.

Some of the proposed uses of Omega 3's are listed below

Prevention of Cardiovascular Events:

Despite the wide spread use of Omega 3's and even recommendations from physicians there is no good evidence that Omega 3 supplements can reduce the risk of heart attacks or strokes in people of average risk. Even among high risk patients and individuals who have had a prior stroke or heart attack the evidence of benefit from Omega 3's is weak.

Lowering Triglycerides:

Fish Oil does seem to lower triglyceride levels significantly but also raises LDL ( bad) and HDL (good) cholesterol levels. Unfortunately this does not seem to result in a corresponding reduction in heart disease.


For conditions such as arthritis the evidence is similarly disappointing. The majority of patients who suffer with arthritis have a type known as osteoarthritis and its clear that in this group Omega 3's offer no benefit. Among a very small minority who have rheumatoid arthritis there may be some benefit but even this is marginal.
So whats the bottom line?

Although the benefits of Fish Oil capsules and other Omega 3 supplements appear to be  in question, the benefits of eating fish are not. Two or more servings of fish per week is a recommended part of any healthy diet. What is clear from these studies though is that we can't try to cram part of a fish into a pill and expect to get the same results.


Michael Melgar

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