For decades, fat and cholesterol have been demonized as culprits for cardiovascular disease and obesity albeit for no good reason as there is no good scientific evidence to support these claims. Only recently has the mainstream science and nutrition community started to recognize that fat isn’t the issue. Instead, as researchers are finding, an increased risk of cardiovascular disease and obesity is more closely linked to the consumption of processed foods, higher intake of carbohydrates, as well as poor lifestyle choices. Let’s take a closer look!
Fat & Cholesterol – What Are They Exactly?
When talking about fat and cholesterol, we tend to lump the two together and think of them interchangeably. However, fat and cholesterol are very different. Fat is a macronutrient. Macronutrients are the nutrients we need in high amounts in our diets. They provide energy, often displayed in the form of “calories” on food labels. Fats are hydrocarbons, meaning they contain hydrogen and carbon components. The hydrocarbon chains that fats are comprised of determine their function and help differentiate between the supposed “good” and “bad” kinds of fats, unsaturated and saturated fat, respectively. The difference between saturated and unsaturated fats has to do with the difference in saturation of hydrogen atoms. Unsaturated fats contain a double bond, meaning they have fewer hydrogen atoms attached to the carbon atoms.1 Saturated fats contain no double bonds.
Cholesterol, on the other hand, is an organic sterol, which is a waxy, lipid substance. 25% comes from our diet, and the liver makes the other 75%.2 Cholesterol, unlike fat, does not provide energy to the body. There are two types of cholesterol, LDL, and HDL. LDL, or low-density lipoproteins, are often referred to as the “bad” cholesterol. HDL, or high-density lipoproteins, is considered to be the “good” cholesterol. HDL is considered “good” because it helps clear excess LDL from the bloodstream, sending it back to the liver to be broken down and excreted. As a side note, it is important to understand that LDL and HDL are not actually “cholesterol”. They are the proteins in the body that carry around cholesterol.
Despite the common belief that we should eliminate fat and cholesterol from our diets, we need to consume these in our diets for regular functioning and body processes. Fats protect your organs, provide energy, aid in hormone production, and help in the absorption of fat-soluble vitamins, such as vitamin A and K. Cholesterol is responsible for the production of sex hormones, building certain tissues throughout the body, and helping in the production of bile in the liver.3 It is also necessary for vitamin synthesis, cellular integrity and hormone synthesis. In fact, certain diseases, such as Smith-Lemli-Opitz Syndrome, where cholesterol cannot be synthesized properly leads to serious issues such as autism and reduced muscle.
Dietary Saturated Fat – Why the bad rap?
In the 20th century, heart disease became an epidemic amongst the American population. Statistics showed that it was the number 1 cause of death. Researchers made a correlation between the high consumption of saturated fat and heart disease because saturated fats were found, in the short-term, to be associated with increased total cholesterol. The problem(s)? There was no solid scientific evidence to back up these claims. The studies and evidence presented were based on animal trials and general assumptions. Experiments were never well controlled in these studies, and researchers never accounted for confounding factors. There was also no evidence from human studies to back up this saturated fat/heart disease hypothesis.
More specifically, researchers also failed to recognize that total “cholesterol” is a flawed marker of heart disease, because total cholesterol includes both “bad” LDL cholesterol, and “good” HDL cholesterol.
What researchers actually found is that, in the short term, saturated fat increases both HDL and LDL cholesterol, and HDL is associated with a lower risk of heart disease.
In reality, there is no such thing as “good” or “bad” cholesterol. You need both HDL and LDL for proper physiological function (LDL is good, and actually helps bring cholesterol into the cells and helps to maintain cellular fluidity). The only time cholesterol is “bad” is when it ends up in the wrong places. Under the influence of inflammation and other factors, this can result in plaque buildup in arterial walls, causing blockages and wreaking havoc on the cardiovascular system. More importantly, it turns out that the type of cholesterol that increases the risk of developing arterial plaques is small sized, dense, LDL particles, in high numbers. The reason for this is that smaller sized LDL particles have a higher chance of being absorbed in the arterial wall becoming oxidized, which is a critical step in the development of atherosclerosis. Larger LDL particles are less susceptible to arterial wall penetration and oxidation. Furthermore, the larger the number of these smaller particles, the higher the chances of these processes occurring.
Interestingly, researchers have found that in the short-term, saturated fat consumption actually helps convert small LDL particles to larger particles.4,5,6 Researchers have actually found that low-carb diets, high in saturated fats, can reduce the risk of heart disease significantly due to the favourable cholesterol profiles obtained following these diets; fewer numbers of small LDL particles, and higher numbers of large LDL and HDL particles.7,8 Low-fat diets do NOT reduce the amount of small LDL particles, and actually, have been shown to result in an unfavorable lipid profile (high small LDL, low HDL, and increase triglycerides).9,10
There are a few large studies (systemic reviews and meta-analyses) that take an in-depth look into all of the data obtained to date on observational studies and controlled trials about saturated fat and heart disease. Here are there conclusions:
- A meta-analysis of prospective epidemiologic studies showed that there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD. More data are needed to elucidate whether CVD risks are likely to be influenced by the specific nutrients used to replace saturated fat.11
- Current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.12
Perhaps most importantly, a recent scientific study from 2017 explored macronutrients and their relationship to mortality and cardiovascular disease from 18 countries in 5 different continents. They concluded the following:
“High carbohydrate intake was associated with higher risk of total mortality, whereas total fat and individual types of fat were related to lower total mortality. Total fat and types of fat were not associated with cardiovascular disease, myocardial infarction, or cardiovascular disease mortality, whereas saturated fat had an inverse association with stroke. Global dietary guidelines should be reconsidered in light of these findings.”13
We’ve already covered why cholesterol is good, and identified that the only time cholesterol is potentially “bad” is when you have an increased number of small-sized LDL particles. Even in these scenarios, this doesn’t mean you will get heart disease, but that you are increasing your risk of heart disease. In fact, cholesterol-lowering therapies do not lower risk of cardiovascular disease.14 Heart disease is a complex phenomenon, and researchers are finding out that it is driven by a variety of factors, including inflammatory and autoimmune factors, as well as genetic and epigenetic factors.
But what about the cholesterol in our diet? Does this impact our cholesterol levels?
It turns out that dietary cholesterol actually has no impact on our blood cholesterol levels. Only a small portion of the cholesterol from our diet actually gets absorbed into the body. Furthermore, when our bodies sense low levels of cholesterol, they ramp up cholesterol synthesis to make up for the lack of cholesterol. In fact, avoidance of dietary cholesterol can result in malnutrition, due to the reduced consumption of healthy foods that also happen to contain cholesterol, and even increased risk of heart attacks.15,16
The most important factors for achieving ffavourableblood cholesterol profiles appear to be of epigenetic origin, and include: 1) decreasing the amount of dietary carbohydrates, 2) elimintation of processed foods, 3) avoidance of inflammatory foods, 4) positive lifestyle choices (like increased exercise frequency).17,18,19,20
Genetics or hereditary factors also play a role in blood cholesterol profiles. The liver is a key player in cholesterol homeostasis and LDL and HDL production, and individuals with genetic conditions that affect the liver are more susceptible to cholesterol issues.21
The Bottom Line
Cholesterol and fat do a whole lot of good for our bodies. Without them, we would have many problems functioning properly. Don’t believe everything you read. Do your research and stay educated about what foods you are putting in your body!
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