Les dette blogginnlegget på norsk her!
We are now on our way out of the most severe epidemic in the Western world’s modern history – the heart attack epidemic. At the start of the 1900’s, heart disease was relatively rare, but from before World War II until the 1970’s there was a marked increase of deaths due to heart disease. In the 70’s every fourth Norwegian man died of heart disease before the age of 75. From the 70’s on, the incidence gradually declined and around year 2000 we were roughly back at the same incidence rate as before World War II. What was it that caused this huge increase in heart disease and why have the incidence rates been on the decrease again during the last 30 years?
All disease occurs as a result of inherited traits and environmental factors. Since the genetic material in the population is fairly constant over time, the reasons for this epidemic must be found in environmental factors – what we eat, what we do and what we expose ourselves to. Living conditions in the western world has changed a lot during this period and many factors have probably contributed to the occurrence of this epidemic.
Tobacco smoking is one of the known risk factors for heart disease and the increase in tobacco use in the post-war years can probably be part of the explanation. But it does not explain it all. Tobacco smoking among men decreased gradually from the beginning of the 60’s, while the proportion of daily smokers among women peaked around 1970 and remained at a stable high until well into the 90’s. If tobacco smoking had been a major cause of the epidemic, one would expect a shift in the incidence curve for heart disease, so that the peak of the heart attack epidemic would be reached decades later for women than for men. The incidence of cardiac deaths was highest around 1970 for both men and women, and it is therefore unlikely that tobacco smoking fully explains the epidemic.
More likely is that the main cause of the epidemic is to be found in the diet. The intake of different types of fats has long been in the spotlight as the causes of heart disease. In recent years, we have become increasingly aware that one particular family of fats is particularly harmful, namely the trans fats.
Moderate amounts of trans fats occur naturally in meat and dairy products from ruminants. From the beginning of the 1900’s we began to produce industrial trans fats. Fish and vegetable oil was saturated with hydrogen gas, thereby producing trans fats. This fat had properties that made it very well suited to be used in industrial food production – it had the right consistency, did not easily turn rancid and not least it was cheap. Norway had a good supply of fish oils and was, along with amongst others the Netherlands, one of the major producers of trans fats. In retrospect we see that this coincides with Norway and the Netherlands having the highest rates of cardiac deaths in Europe during this period. The bulk of trans fats consumed in the Norwegian diet came from margarine, but also semi-finished food products and certain baked goods were significant contributors. The consumption of trans fats in Norway peaked around the late 1950’s.The proportion of trans fats in margarine has since been gradually reduced and since the end of the 90’s Norwegian margarine contains minimal amounts of trans fats.
The dangers of trans fats have become better and better documented in the recent years and in response to this, in 2014, Norway introduced the strictest regulation of trans fats in food in Europe. It is now forbidden to sell products that contain more than 2% of industrial trans fats. The history of trans fats remains a daunting reminder of how wrong things can go if industrially manufactured products are uncritically used in food.
Erlend Hassel, PhD student at CERG