Updated: Jul 10, 2018
When we hear it, a lot of the time the first things that come to mind are things like heart attacks, clogged arteries, and bacon & eggs.
But what is cholesterol?
Even with all of the information we have available on cholesterol, we still don't completely understand it. With that being said, the current understanding of it is as follows...
Cholesterol is a molecule in our bodies that is derived from acetyl-CoA (which is the molecule that our bodies ultimately break everything we eat into to convert the energy we eat in food into energy that we can use). Cholesterol is absolutely essential to life and it is so important to our bodies that nearly all tissues in the body are able to make it. About two-thirds of cholesterol in the body each day is synthesized by the liver.
Cellular membrane function depends on this molecule. It also plays a key role in the synthesis of steroid hormones (including Vitamin D) and bile salts, as well as the absorption of dietary fat.
Your blood levels of cholesterol are mostly genetically dictated and adjust accordingly with your diet. For example, as dietary cholesterol increases (the amount of cholesterol you eat through food), the less your body will make its own cholesterol. The same happens in the opposite direction in that the less cholesterol you consume, the more your body will produce on its own.This is true in the absence of metabolic disturbances, which are not uncommon and are often treated with statin drugs that reduce the body's production of cholesterol allowing one to lower blood cholesterol levels. Statins downregulate the enzyme (HMG-CoA) that assists in the conversion of acetyl-CoA to cholesterol. Addressing the metabolic disturbances through physical activity and dietary changes are also ways to manage one's cholesterol levels.
So what's the worry?
If cholesterol is a naturally occurring molecule in the body that is essential for life, why would we be concerned at managing our body's blood cholesterol levels at all?
The thing is, the molecule itself is not particularly water-soluble, meaning that it can't travel around in the body on it's own. In order for it to travel around the body, it has to be escorted by other molecules called lipoproteins. There are several different types of these lipoproteins (five classes, each class being divided into subclasses) but the ones we look at most often are called HDL and LDL.
HDL stand for "high density lipoprotein". This type of lipoprotein is made up of the least amount of triglycerides (storage form of fatty acids) and cholesterol, and escorts cholesterol primarily to the liver for excretion.
LDL stands for "low density lipoprotein" and is made up of the highest amount of triglycerides and cholesterol. The job of this molecule is transporting cholesterol and triglycerides to our cells so they can use these molecules for membrane construction, conversion in to hormones, and storage.
You may hear HDL referred to as the "healthy cholesterol" and LDL as the "bad cholesterol." Although there is some merit to this, taking this stance on cholesterol is overly simplified and misleading. As we've discussed, both types have important roles to play in our body, transporting cholesterol and other molecules that are not particularly water-soluble. With this clarification, we can explore this concept further.
The DL on LDL
The size of each LDL molecule can vary, meaning it can be small and dense or it can be large and fluffy. When our LDL molecules are small and dense, we start to run into problems. These LDL molecules are much more likely to get stuck in endothelial tissues while they are delivering cholesterol to cells around our body, especially in combination with excessive inflammation.
When these LDL particles get stuck in our vascular system, the risk of developing "plaques" increases. These plaques can start to build up in the lumin (interior space) of our blood vessels (this build up is called atherosclerosis) which can lead to health complications including (you guessed it...) a heart attack.
What you eat influences the shape and size of these molecules. Consuming refined carbohydrates (i.e. high amounts of sugar, processed breads and pastries, etc.) and trans fats (i.e. as found in margarine) result in smaller and denser lipoproteins.
What you eat also influences the amount of inflammation in the body. Inflammation in the lumen is triggered by oxidized (damaged) fats bound to LDL particles (among other inflammatory triggers outside the scope of this article). The particularly inflammatory fats include polyunsaturated fatty acids (or "PUFAs") which include many commonly used vegetable oils such as canola oil, soybean oil, etc that, when exposed to light/heat, become damaged and travel through our bodies bound to LDLs.
Contrary to popular belief, consuming dietary cholesterol isn't the pressing issue when it comes down to reducing the development of arterial plaques. It turns out that our bodies are a little more complex than that.
With that being said, there is a subset of people who are genetically susceptible to extremely high levels of blood cholesterol. The physiology of these people fall outside of the regulatory processes of physiology and should be addressed under medical supervision and intervention, which may include restricting their dietary cholesterol to manage overall cholesterol blood levels.
As the interest in understanding how food impacts our physiology grows, we are beginning to see and learn a lot more about how we can effectively improve our health through our diet, but pushing through deeply imbedded and long held beliefs about health and diet is the first step in opening up the conversation.
Stay tuned to our blog for more information and tidbits on everything food and physiology!