I was brought up on a spoonful of cod liver oil a day, not sure if that did any good at the time though. I remember I didn’t like it, not that I had much of a say. I have since resisted all overtures to take a daily omega-3 fish oil capsule, although I have praised them in previous blog posts. The science seemed to be clear, omega-3 fatty acid supplements looked to be one of the few supplements with a real health benefit. Now I take all this back.
I know, nutritional science is confusing and nutritionists seem to change their recommendations regularly. One day a green capsule a day of some obscure substance is a must and a red tablet should be avoided. The next day it is the opposite. What is an ordinary person to do? Well, at least it creates more work for nutritionists (and EFSA’s Panel on Dietetic Products, Nutrition and Allergies) and some fodder for sensationalising newspaper articles.
Eskimo diet hypothesis proven wrong
As it happens, the current recommendation to eat more oily fish as part of a heart healthy diet has mainly been based on a landmark study from the 1970s by two Danish investigators, Bang and Dyerberg. They had been told that the Greenland Eskimos had a low prevalence of coronary artery disease and set out to study their diet. They described the Eskimo diet as consisting of large amounts of seal and whale blubber (i.e. fats of marine animal origin) and suggested that this diet was a key factor in the alleged low incidence of coronary heart disease. This started an avalanche of studies that focused on the cardioprotective effects of the Eskimo diet and created an industry around fish oil supplements containing omega-3 fatty acids.
Building on 40 years of new research since the Danish findings, a team of scientists recently conducted a review of the resulting literature to examine whether mortality and morbidity due to coronary artery disease are indeed lower in the Eskimo population compared to their Caucasian counterparts. Most studies reported that the Greenland Eskimos as well as the Canadian and Alaskan Inuit had coronary artery disease as often as the non-Eskimo/Inuit populations.
Unfortunately, Bang and Dyerberg’s studies from the 1970s failed to actually investigate the cardiovascular health of the the Eskimo population, and as a result the cardioprotective effects of their dietary findings were unsubstantiated. They rather relied on annual reports produced by the Chief Medical Officer of Greenland covering cardiovascular deaths in the region. Because of the rural and inaccessible nature of Greenland, it was difficult to keep accurate records of cardiovascular disease affecting the population and the validity of Greenland’s death certificates have been questioned. Actually, 20% of the death certificates were even completed without a doctor examining the body.
Use of omega-3 fatty acids ambiguous
The new review did not only show that the Eskimos and Inuits have a similar prevalence of coronary artery disease to the rest of the population, but in fact have very high rates of mortality due to stroke. Overall, their life expectancy is approximately 10 years less than the typical Danish population. It is thus remarkable that instead of labelling their diet as dangerous to health, it was proposed that dietary intake of marine fats prevents coronary arterial disease and reduces atherosclerotic burden.
It is clear that many recent large and well-designed studies have shown ambiguous or negative results regarding the cardioprotective properties of omega-3 fatty acids and fish oil supplements, and yet they are still widely recommended as part of a heart healthy diet plan, supporting a billion dollar industry selling fish oil capsules based on a hypothesis that was questionable from the beginning.
I know what I will do. I will continue to stay away from fish oil capsules, but keep eating my weekly salmon or herring meals because I enjoy them.