Fish Oil and Heart Disease: The Messy Reality

Written by: Corey Washington

Primary Source: Zero Ideology

I eat a lot of fish mainly because I think it is good for my heart. I came to this belief after reading studies years ago indicating that consumption of omega-3 fish oils reduced rates of cardiovascular disease (CVD), which is the main cause of death of people in my family. Over the past decade, the view that fish oils are good for CVD became the scientific consensus as depicted in the popular press and a nutritional dogma.

An interesting paper just published in the Canadian Journal of Cardiology (““Fishing” for the origins of the “Eskimos and heart disease” story. Facts or wishful thinking? A review“) by George Fodor and colleagues argues that the original study connecting fish oil to lower CVD was based on a flawed premise.

During the 1970s, two Danish investigators, Bang and Dyerberg, upon being informed that the  Greenland Eskimos had a low prevalence of coronary artery disease (CAD) set out to study the diet of this population. Bang and Dyerberg described the “Eskimo diet” as consisting of large  amounts of seal and whale blubber (i.e. fats of animal origin) and suggested that this diet was a key factor in the alleged low incidence of CAD. This was the beginning of a proliferation of studies that focused on the cardioprotective effects of the “Eskimo Diet

Bang and Dyerberg got their data on CVD in Eskimos from annual mortality reports produced by the Chief Medical Officer in Greenland. Fodor maintains that these records were not reliable. No direct study of the CVD risk in Greenland Eskimo’s was published in until 2008.

The alleged absence of CAD in Greenland Eskimos is a paradoxical finding, given that this is a population mainly sustained on a diet high in animal fat, absence of fruits and vegetables and other important nutrients; in other words, a diet which violates all principles of balanced and heart-healthy nutrition.

The totality of reviewed evidence leads us to the conclusion that Eskimos have a similar  prevalence of CAD as non-Eskimo populations, [that] they have excessive mortality due to cerebrovascular strokes, [that] their overall mortality is twice as high as that of non-Eskimo populations and [that] their life expectancy is approximately 10 years shorter than the Danish population.

It seems that until recently there has been little effort to check the fundamental assumption behind the original research, and even at the time there was evidence that it was wrong. Over the years, people simply repeated it until it became gospel. Another recent review argues that CVD rates have been rising among Eskimos population due to changes in lifestyle.

The CVD increase was thought to be related to the high prevalence of cigarette smoking, ongoing lifestyle changes that favored physical inactivity, and consumption of non-marine fatty acids, leading to an increase in obesity and diabetes

Relative Risk of CVD in Top versus Bottom Third of Fatty Acid Intake

Relative Risk of CVD in Top versus Bottom Third of Fatty Acid Intake

What is puzzling is that that there is still pretty good evidence that consumption of omega-3s reduces the risk of CVD. Here’s a key figure from a recent meta-analysis summarizing the association between self-reported omega-3 intake and CVD from 32 prospective cohort studies (512,420 participants, 15,945 incident coronary outcomes, average follow-up time 5 to 23 years).

The figure illustrates the relative risk (rr) of developing CVD between individuals in the top and bottom third in omega-3 intake. People who consume high amounts of omega-3s are slightly less likely (rr = 0.87) to develop CVD than those who consume only small amounts. Other meta-reviews back up this contension.

So it appears that Bang and Dyerberg may have gotten it right, even though their study population did not have lower rates of CVD.

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