By Lucy Wing
The difference between saturated and unsaturated fats is a fairly well-known concept, but even the existence of polyunsaturated fat, linoleic acid, is not as well known. Although you have probably been consuming it for your entire life, you may not be aware of the presence of linoleic acid in your diet. As an unsaturated fat, linoleic acid affects our body’s cholesterol levels. The dangers of serum cholesterol are defined by both high and low-density cholesterol, which is simply a measure of the lipid composition in our blood. High levels of low-density cholesterol develop into plaque-like deposits within one’s arteries, causing restricted or more difficult blood flow, which can eventually cause significant cardiovascular complications. Products like to advertise that they help to reduce cholesterol and improve heart health, but what you don’t see are the advertisements about linoleic acid. Linoleic acid is not as often referred to because its effects are just recently being re-analyzed, and somewhat controversial to common belief.
In 1968, Dr. Ivan Frantz asked a controversial question regarding the connection between linoleic acid and serum cholesterol. Does lowering an individual’s serum cholesterol via a higher proportion of dietary linoleic acid reduce the chances of coronary heart disease and early death due to cardiovascular complications? Frantz set up The Minnesota Coronary Experiment to address this question. The study ran from 1968 to 1973. I must add that the study acquired what would be considered an unethical perspective to modern standards. The research participants were chosen because they were residents of hospitals. The control group continued to eat their normal diet provided by the hospital dining services. The experimental group ate food only cooked in unsaturated fats, namely corn oil. When the study concluded, Dr. Ivan Frantz was puzzled by the results as there was no statistically significant relationship showing that lowering cholesterol reduced the rate of death from coronary heart failure. This was his life’s research, and the results were completely contradictory to his hypothesis, so the results were largely left unpublished.
For years, data regarding linoleic acid relating to heart conditions and health was left untouched. Modern diets claiming to improve life expectancy from a highly unsaturated fat diet became widely popular. It was not until 2016 that evidence suggesting otherwise was published by Dr. Christopher Ramden and his team. Dr. Ramden had come upon the vague information on Dr. Frantz’s study and decided to conduct a meta-analysis of similar studies conducted across the globe. They used Dr. Frantz’s hypothesis as a way to conduct their data analysis. In a normal diet, an individual’s diet contains approximately 3-6% linoleic acid (kcal), in the experimental group, their daily calorie intake was approximately 13% linoleic acid. The results of the meta-analysis did in fact show a lowering in the serum cholesterol level so the participants, but this lower cholesterol did not correlate to a lower rate of coronary heart disease and death. As a matter of fact, it was on the contrary. Although there was no direct information on whether or not this type of diet can improve life expectancy, the analysis did show, however, that in people over the age of 65, a lowering of serum cholesterol can lead to an increased chance of death from coronary heart disease. According to the results from the study, a 30 mg/dL decrease in serum cholesterol increased the chance of death by 22% in all participants. If the participant was over the age of 65, the chance of death increased to 33%.
The idea of a healthy diet with unsaturated fats and oils being incorporated has been so ingrained in the dietary fads of modern society that this scientific shift in knowledge has been largely ignored. If it took over 40 years for the effects of linoleic acid to be rediscovered and re-analyzed, how much time will it take for the results of the 2016 study to be accepted? This shift in scientific knowledge has the ability to save people’s lives and prevent cardiovascular-related illnesses and death. It also opens to the door for more research raising controversial questions about widely accepted nutritional information.
Ramsden, C., Zamora, D., Majchrzak-Hong, S., Faurot, K., Broste, S., Frantz, R., . . . Hibbeln, J. (2016, April 12). Re-evaluation of the traditional diet-heart hypothesis: Analysis of recovered data from Minnesota Coronary Experiment (1968-73). Retrieved September 28, 2020, from https://www.bmj.com/content/353/bmj.i1246