The scientific interest for fish oil is enormous. Since September of last year, almost 800 articles about fish oil have been publicised in established journals.
This is with very good reason. Notably, fish oil contains two types of fatty acid, both of which are attributed with having a positive effect against many serious chronic diseases. If this is even in part true, it should be considered very imprudent not to receive fish oil every day. The primary disease that it is believed to prevent is cardiovascular disease, but there is also good reason to believe that fish oil works against, for example, depression, dementia, arthritis, and diabetes, even though there is no concrete evidence as of yet in these areas.
The two fatty acids are called EPA (eicosapentic acid) and DHA (docosahexa-enoic acid). Together they compose one third of the contents of fish oil and two thirds of the concentrated fish oil products, which can be found in capsule form.
Much attention has been given to DHA which, contrary to EPA, is found in large amounts in the brain (14% of the cerebral cortex’s fat content) and in even greater amounts in the retina (22%). Breast fed children have much higher concentrations of DHA in their brains than bottle fed children (babies cannot produce DHA themselves). It is hard to believe that there are no consequences of receive too little.
There are an incredible number of adults who take supplements of fish oil daily to maintain their cardiac health.
But does it work?
Six months ago a group of English researchers maintained that it does not. They had looked at all of the relevant studies and then calculated the averages of their results. In their opinion, the results showed that fish oil neither protects the heart nor lengthens life span. This is just the opposite of what was previously believed.
This meta-analysis was strongly criticized and, as discussed in another of The Danish Vitality Council’s newsletters ("Fish Oil – Still Indispensible!") there were so many question raised by the analysis that it lacked credibility.
Doubts regarding the dosage
This is now supported by a summary article from the distinguished American Journal of Clinical Nutrition. According to the head authors, a group of researchers undertook an extensive survey, taking “a large step forward” in spreading light into the darkness. There is no longer much doubt that fish oil reduces the overall risk of premature death and the risk of death due to a blood clot in the heart, and that it possibly reduces the risk of stroke.
Completing this survey was an extensive project. The researchers first read summaries of 8,039 scientific articles. They then picked 842 relevant articles from these to be read in their entirety. 46 articles of these 842 met the strict quality requirements and were studied further. The researches requirements regarded the length of the studies (at least one year), the dose of the fish oil given, and proper documentation.
How big are the advantages and how much fish oil should one take? This actually cannot be answered with certainty! The studies surveyed were too different regarding the dose given, the type of participants, the time taken, and so on to answer such questions. It is simply bad form to establish any averages, as the English researchers did. But if one wants to draw conclusions anyway, it is safe to guess that the overall risk of premature death and the risk of death due to cardiac disease can be reduced by 15-20% or more.
It is however nearly certain that fish oil helps those who have had a blood clot in the heart and wish to avoid another. But what about the dose, how much should one take?
Until more information surfaces, we should rely on the American Heart Association’s recommendations, which are based on estimates. Heart patients should receive 1 gr. EPA +DHA daily. This is the equivalent of about two large capsules of 1 gr. concentrated fish oil. Everyone else should receive at least half this amount. This can be achieved by eating fatty fish for dinner 1-2 times weekly.
There is a lot of knowledge lying in wait, not just about fish oil and the heart. More results will surface in the next year. While we wait we wait in the knowledge that it is important to get enough.
- Wang C et al. n-3 fatty acids from fish or fish-oil supplements, but not á-linolenic acid, benefit cardiovascular disease outcome in primary- and secondary-prevention studies: A systematic review. Am J Clin Nutr 2006;84:5-17.
- Deckelbaum R et al. n-3 fatty acids and cardiovascular disease: navigating toward recommendations. Am J Clin Nutr 2006;84:1-2.
- Distribution, interconversion, and dose response of n-3 fatty acids in humans. Am J Clin Nutr 2006;83(suppl):1467S-76S.