First published in the December 6, 2013 issue of The Vault Magazine.
If you research ice cream sales and drownings in swimming pools, you will find they are correlated. That is, as ice cream sales increase, so too do drownings in swimming pools, and vice versa. To say that ice cream causes people to drown is of course absurd. More likely, heat waves cause both variables to increase.
If you research ice cream sales and drownings in swimming pools, you will find they are correlated. That is, as ice cream sales increase, so too do drownings in swimming pools, and vice versa. To say that ice cream causes people to drown is of course absurd. More likely, heat waves cause both variables to increase.
This logical fallacy is common in population studies. Researchers look at large groups of people and analyze their lifestyles. They then look at the health of this population and try to determine if certain lifestyle factors are associated with poor (or positive) health outcomes.
When they find relationships it often leads to pronouncements of causation which quickly spread.
The ubiquity of omega-3 fatty acids is testament to the problems this can cause.
Omega-3 fatty acids (AKA omega-3s, EPA, DHA, fish oil, etc.) occur most commonly in fish. They represent a $25 billion global market, mostly in infant formula, fortified foods, and supplements.
From this one would think the evidence is conclusive that they improve health.
Sadly, this is not the case.
It all started in the 1970s when Danish researchers looked at Greenlandic Eskimos, a population with extraordinarily low rates of heart disease. Their diet consisted almost entirely of marine animals and their blood showed massive levels of omega-3s.
Assuming correlation equals causation, they attributed the low rates of heart disease to the high rates of omega 3s.
The notion spread. Study after study showed that high rates of fish consumption correlated with lower risk of heart disease.
Today omega 3s appear in every form imaginable, from pills to yogourt. They are promoted for infant development, intelligence, autism, ADHD, heart disease, Alzheimer’s and more.
Dr. Oz says they are 1 of 5 "critical" supplements every woman should take, and good for "just about every single part of your body".
To determine causality, researchers conducted randomized controlled trials, the gold standard in medical research, on omega 3 supplements.
The Cochrane Collaboration reviewed many of these studies and the conclusions are clear.
There is simply NO evidence that supplementation with omega-3 fatty acids causes any of the health benefits attributed to them.
Populations with high fish consumption have lower rates of heart disease than those with low fish consumption.
This does not mean fish consumption causes low rates of heart disease.
It is likely just one component of an overall healthier lifestyle.
To think that in the infinitely complex interaction between lifestyle and health that ONE chemical component of ONE food group is responsible for this effect is a leap of faith.
To take that one ingredient and put it into every food and supplement we consume and think we will reap healthy rewards stretches the boundaries of reason.
It’s a shortcut to health that rarely works.
Next time: What multivitamins and the Nobel Prize have in common.
References
1. http://mnstats.morris.umn.edu/introstat/public/instruction/causation.html
2. http://www.innovation.research.wvu.edu/r/download/158952
3. http://www.sciencedirect.com/science/article/pii/S0140673671916588
4. http://www.isodisnatura.ca/history_of_omega-3s.htm
5. http://content.onlinejacc.org/article.aspx?articleid=1117937
6. http://www.doctoroz.com/videos/daily-dose-omega-3
7. http://www.ncbi.nlm.nih.gov/pubmed/22968891
8. http://www.ncbi.nlm.nih.gov/pubmed/23814120
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