Anybody who hasn’t heard yet that omega 3 fatty acids (found in fatty fish, like sardine, salmon, trout, mackerel) are good for your heart must have been asleep for the past 40 years. This has been so thoroughly accepted that it reached the level of axiomatic fact. Where did this notion originate from?
In the 1970s, two Danish investigators, Bang and Dyerberg, published a landmark study that connected the low incidence of coronary artery disease (CAD) among the Eskimos of Greenland to their diet, rich in whale and seal blubber. Well, nothing lasts forever; science works by repeatedly examining and re-examining assumptions and theories. If it didn’t, Galen would still reign supreme.
(BTW, where did this notion originate from? Greenland, that ice-covered island that should have been named “Iceland”, except that this name had been already bestowed on a warm and truly green island.)
The new research
Using 40 years of new information and research, a team of Canadian investigators set out to reexamine Bang and Dyerberg’s study of Greenland Eskimos and CAD. The data collected through this new investigation shows that Eskimos, in fact, have a similar prevalence of CAD to non-Eskimo populations. In addition, they have very high rates of mortality due to cerebrovascular events (strokes). Overall, their life expectancy is approximately 10 years less than the typical Danish population and their overall mortality is twice as high as that of non-Eskimo populations.
What went wrong with the original study?
Bang and Dyerberg relied mainly on annual reports produced by the Chief Medical Officer of Greenland to ascertain CAD deaths in the region. The 2014 study has identified a number of reasons why those records were likely insufficient—mainly that the rural and inaccessible nature of Greenland made it difficult for accurate records to be kept and that many people had inadequate access to medical personnel to report cardiovascular problems or heart attacks.
In fact, researchers have now found that concerns about the validity of Greenland’s death certificates have been raised by a number of different reports and that, at the time, more than 30% of the population lived in remote outposts where no medical officer was stationed. This meant that 20% of the death certificates were completed without a doctor having examined the body.
Does it mean that fish oil is useless?
The fact that literally thousands of studies cite Bang and Dyerberg’s studies doesn’t mean that the whole theory of fish oil’s protective effect on the heart is per se invalid. Lest we forget: Whales and seals are mammals, not fish. Their blubber is not much different in composition from cattle fat. In fact, cows are close phylogenetic relatives of whales. This may account for the poor cardiovascular health of the Eskimos. So, we still have the question of the benefit of “real” fish oil.
Back in May 2013, for example, Italian researchers reported in the New England Journal of Medicine that omega-3 fatty acid supplements (the “active ingredient” in fish oil) did nothing to reduce heart attacks, strokes, or deaths from heart disease in people with risk factors for heart disease.
Further, a study by scientists at the Fred Hutchinson Cancer Research Center in Seattle linked eating a lot of oily fish or taking potent fish oil supplements to a 43% increased risk for prostate cancer overall, and a 71% increased risk for aggressive prostate cancer. Their report was published in the Journal of the National Cancer Institute. The report from the Fred Hutchinson researchers is the latest to sound a warning about too much omega-3 fatty acids.
Take home lesson
Omega 3 fatty acids are anti-inflammatory, and inflammation is well-established as a factor in cardiovascular disease and cancer. But to conclude that Omega 3 fatty acids are protective against those diseases, based on their biochemical properties, is a huge leap of faith. Food contains thousands of compounds, and we know close to nothing how each individually affects our health, and what effect they have in combination.
So rather than trying to over-analyze our foods based on flimsy science, why not stick with real food. Eat plenty of fish, veggies, and fruits—a diet that has been shown to be good for us—and don’t worry about their chemistry.