Learn the difference between “good” and “bad” cholesterol and what impact fat has on our health
The story of nutritional science is not a sober-minded, research-based one. Instead, it falls under the “Great Man” theory of history. Strong personalities — Ancel Keys being the key figure — steered events eventually leading up to the “diet-heart hypothesis.” This hypothesis was formed after Keys found a correlation between fat intake and death rates from heart disease in six countries.
Saturated and unsaturated fats
Understanding the difference between the two most important types of fat, saturated and unsaturated fats, can help how they affect our bodies. The difference between both can be better understood by analyzing the chemical structure. Fats are made of chains of carbon atoms surrounded by hydrogen atoms. The two types of atoms are connected by two type of bonds, single and double bonds. A bond is a chemical term used to describe the way two atoms are linked together.
A fat bond can be imagined as a handshake between a carbon and hydrogen atom. The single bond is a connection by one hand while the double bond is like both atoms hold both hands together. Saturated fats are composed of single bonds while unsaturated fats have at least one double bond.
Fats from animal sources such as contained in meat, butter, cheese are saturated fats. Vegetable oils such as olive oil are unsaturated fats. The difference in bonds explains why saturated fats tend to be solid at room temperature while unsaturated fats tend to be liquid.
Saturated fatty acids contain no double bonds, which is why they cannot take on any new atoms. They are “saturated” with hydrogen atoms. Having no “loose hands” gives them the ability to be packed together densely, giving them a solid structure at room temperatures like lard, suet, tallow, and butter.
Unsaturated fats have a “loose extra hand” which can grab other molecules such as oxygen from the air, which is why unsaturated fats oxidize or rancid quickly when exposed to air.
The connection between cholesterol, heart disease, and saturated fats
Nutritionist Ancel Keys combined his passion with physiology with his work in nutrition and made a discovery during an experiment he conducted in 1958. He found that a person’s fat intake directly affects levels of cholesterol, and high levels of cholesterol, in turn, can increase the chance of getting heart disease.
But cholesterol is vital for our bodies, every cell of our body has some cholesterol in its membrane, acting as a barrier for what gets in and out.
Cholesterol also is the primary element which builds up plaque in our arteries. Plaque thickens the arteries walls thus restricting blood flow and consequently increasing blood pressure. The combination of these factors can lead to heart disease.
Keys found in an experiment that participants who ate saturated fats gained higher cholesterol levels while levels of cholesterol went down in participants who had an unsaturated fat diet.
It is mainly from Key’s realization that the general idea came that saturated fats are unhealthy while unsaturated fats are healthy.
The diet-heart hypothesis
The assumption that saturated fats cause heart disease was quickly established in the mainstream through Key’s influence on prominent institutions such as the American Heart Association (AHA), and the TIME magazine.
Another study called the Framingham Study concluded that people were more likely to suffer from heart disease when they had high levels of cholesterol. This combined with the AHA report lead to the widespread acceptance of the diet-heart hypothesis.
But at least two studies have opposed Keys’ hypothesis. The first study was performed in the 1950s. The study found that individuals who cut back on red meat had lower cholesterol levels and blood pressure and thus faced a lower risk of heart disease.
The curiosity came when 26 members of the low-read-meat group and 6 members of the control group died. None of the 6 members in the control group died due to heart disease while 8 deaths of the low-read-meat group were caused by heart disease.
Another challenge to the diet-heart hypothesis was found when a group of researchers measured the blood pressure of Masai tribesmen. The tribe had a diet which consisted of 60% of saturated fats such as meat, blood, and milk. The tribesmen’s blood pressure was 50% lower than an average American.
While studies against the diet-heart hypothesis have mostly been ignored, the data still generated motivation to further study the link between food and heart disease in the scientific community.
Trans fats as a replacement for saturated fats didn’t solve the problem
The diet-heart hypothesis became so influential that the food industry had to come up with an alternative for saturated fats.
Unsaturated fats were not ideal because they remained liquid at room temperature, and something as solid as fat was preferred. In the late 1980s, the industry came up with a process called partial hydrogenation. The process consists of saturating oils with hydrogen to make them thicker.
Soon enough partial hydrogenation was widely applied in all kinds of foods like cookies, margarine, and potato chips. The problem, however, was not solved, it turned out that hydrogenated vegetable oil wasn’t healthy. A byproduct of the hydrogenation is trans-fatty acids, which are dangerous to our health. These types of fat don’t usually occur in nature but are a byproduct of artificial processing. Although the first research showing this was published in the 1960s, it was not until 1994 were a study conducted by a researcher named Joseph Judd drew the attention of the public.
In the study, participants were divided into three groups. One group consumed a diet high in olive oil, the second group a diet high in trans fats and the third group consumed a moderate amount of trans fats.
After Judd had found that a diet high in trans fats caused a rise in cholesterol levels, people began to oppose the use of trans fats in processed food. Once again food producers had to come up with a solution.
Even vegetable oils are hazardous to health when heated
Some food makers started using palm oil, oil from genetically engineered soybeans or even liquid vegetable oils such as sunflower oil. But vegetable oils go rancid, so they weren’t a good choice for packaged foods.
Vegetable oils are useful for frying. However, a 2010 report from the Agency for Research on Cancer illustrated that when vegetable oils are heated to temperatures used in most fryers, they likely release substances which are carcinogenic to humans.
Gerald McNeill, the vice president of one of the country’s largest suppliers of edible oil, told the author about the scary consequences of using vegetable oils for frying which he had observed shortly after restaurants went trans free in 2007.
When those oils are heated, they produce a compound called aldehyde which interferes with DNA and formaldehyde which is toxic. Furthermore, oxidized oils form polymers which create a “thick gunk.” The gunk is so sticky, it sticks to the bottom of fryers, and clog’s up drains.
The gunk also infests the surroundings through the mist coming off the fryer and collecting in all kinds of places like floors, walls, workers uniforms, etc. This sticky substance wouldn’t easily go off through hand scraping and not even with sand blasters.
HDL-cholesterol vs. LDL-cholesterol
It turns out that there are two types of cholesterol, HDL which is the bad cholesterol and LDL which is good. They are characterized by the density of their carriers or lipoproteins. The carriers help cholesterol traveling through our veins and arteries.
LDL or low-density lipoproteins were associated with people who were overweight, smoked, had high blood pressure and didn’t exercise. While LDL or high-density lipoproteins were more abundant in people, who did the opposite, people who exercised didn’t smoke and had a healthy bodyweight.
LDLs fix cholesterol while HDLs clear cholesterol from arteries. Studies suggested that HDL-cholesterol helps fight heart disease.
Heart attacks among people with low HDL-cholesterol were shown to be 8 times higher than among people with high HDL-cholesterol.
The lesson: Raising HDL-cholesterol seems to be the best way to combat heart disease.
Despite not being as effective, many organizations like the AHA focus still focus on lowering LDL-cholesterol levels.
Low carb diets have shown to increase good cholesterol (HDL)
The first low-carb diet has been around since 1863. In 1919 physician Blake Donaldson found that a low-carb diet helped his patients to lose weight, fight heart disease, gallstones, and diabetes.
Challenging the low-fat dogma, cardiologist Robert Atkins wrote the bestseller “Dr. Atkins” in 1972 which popularized the Atkins diet. This diet showed to increase a person’s HDL-cholesterol in studies performed in the 1990s.
[However, ketogenic diets like the Atkins diet have been shown to be dangerous as they can cause irregular heartbeats and are linked to many deaths. To learn more read the Summary of Eat to Live.]
The main lesson from this book: Sort out good fats from bad fats and eat less (refined) carbs.
Personal note: Having read nearly a dozen bestselling books about nutrition it seems to me that plant-based diets are the biggest player when it comes to preventing diseases. Check out the Summary of the China Study for more details. Also, watch this very good critique of the book.
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Also published on Medium.