Most people, when they think of the term cholesterol, associate it with something bad, something dangerous to one’s health. But, is this the case? What exactly is cholesterol and does it play a role in our health? For the next two health articles, we will learn about cholesterol, its function in our body, what happens if we have too much cholesterol, and how to control how much cholesterol we have in our body.
What is not commonly known is that cholesterol is not only good for us, but it is absolutely necessary for the proper functioning of our body. Cholesterol is a fat, a rigid, waxy substance, that is produced by every cell in our body. If our cells need extra cholesterol, beyond what they can make themselves, our liver is the primary place where cholesterol is made and is then transported to the cells. The liver produces 75 per cent of the cholesterol we need. We do not need cholesterol in our diet for our bodies to synthesize cholesterol. Our body actually monitors our cells, and if it senses that a cell does not have enough cholesterol, it will produce more. Your liver produces about 1,000 mg of cholesterol a day. However, the average diet adds another 300 to 500 mg of unnecessary cholesterol a day.
Cholesterol has four main functions. As to how it functions in our cells, think of cholesterol as a brick. You need bricks to build the structure of a house. Your cell walls use cholesterol as bricks, so that the cells have a three-dimensional structure. It is found in every single cell in our body. Cholesterol also protects and repairs cell walls so that they are appropriately permeable, allowing only what is needed to pass in and out of each and every cell in your body. Another function of cholesterol is that it makes up digestive bile acids in the intestine. Bile acids are essential for the absorption of fats, oils and fat-soluble vitamins (A, E, K) from the small intestine. Without bile acids, our bodies would not be able to digest the fat from our food. Cholesterol also enables the body to manufacture sex and stress hormones, such as progesterone, estrogen, testosterone, and cortisol. Cholesterol is necessary to convert the Vitamin D we receive from the sun into the form of Vitamin D that our body can use.
So, what is the problem with cholesterol? At normal levels, it is an essential substance for the body’s functioning, but if levels in the blood get too high, it causes many serious health problems. High cholesterol levels are considered a “silent” health risk. Unless blood cholesterol levels are checked via a blood test, often the first time one becomes aware of a high cholesterol level is because of a serious health event such as a heart attack.
All animals synthesize cholesterol; therefore when people eat an animal-based diet, they ingest unnecessary amounts of cholesterol, on top of what is synthesized from their own body. And, in fact, receiving too much cholesterol from animal-based foods is a significant cause of dangerous levels of cholesterol in our body.
When a blood test for cholesterol levels is done, levels of LDL and HDL are done at the same time. The levels of these other substances are just as relevant, if not more, than the actual amount of cholesterol in the body. So, what is the significance of these other substances? Because cholesterol is a fat, it cannot mix with blood, which is water-based. So, in order for it to travel through the blood, it must be attached to something that allows it to be water-soluble. It is therefore carried around the body in the blood by attaching to lipoproteins. A lipoprotein is a water-soluble protein that combines with and transports fat through the bloodstream. The two main types of lipoproteins are LDL (low-density lipoproteins) and HDL (high-density lipoproteins).
LDLs make up the majority of the cholesterol in the body. The main structural difference between LDL and HDL is their compositions. Approximately 50 percent of the weight of an LDL particle is cholesterol and only 25 percent is protein. High-density lipoprotein particles, on the other hand, consist of 20 percent cholesterol by weight and 50 percent protein. Since protein is more dense than fat, HDL particles are more dense than LDL particles, hence the names “high-density” and “low-density” lipoproteins.
Both lipoproteins are necessary for the transportation of cholesterol in the blood, but the main functional difference between the two is that they deliver cholesterol to different parts of your body. Low-density lipoproteins—the primary carriers of cholesterol—bring cholesterol to cells where needed throughout your body. High-density lipoproteins, on the other hand, carry excess cholesterol away from your heart and other organs and deliver it back to your liver. For example, if your liver thinks the ovaries need more cholesterol to produce estrogen, the liver produces new cholesterol, bundles it with a protein in the form of an LDL and sends it into the bloodstream. To reclaim unused LDLs, your liver bundles cholesterol into HDLs, which pass through your body and collect stray LDLs. When these HDLs return to the liver, it recycles them or uses them to build bile acids. Excess LDLs can also be eliminated from the body through the liver.
So, what is the reason that LDLs are referred to as the “bad” cholesterol; whereas, HDLs are known as the “good” cholesterol? They are both necessary to our health. They both serve a function in our body, and we cannot live without the presence of both. If the levels of LDL and HDL remain at a healthy level, there is no problem.
However, ingestion of fatty foods can increase the amount of LDLs in our body. If the liver detects that there is an increase in cholesterol in the body, it will synthesize more LDL to transport this cholesterol. Also, certain types of fats, specifically saturated fats and trans fats, increase the manufacture of LDLs in the body, through a mechanism which is unknown. We will learn more about the influence of our diet on cholesterol levels next month.
If the body contains too much cholesterol in the form of LDLs, it can cause cholesterol to build up within your arteries, causing damage to the blood vessel walls. This is why LDL is commonly referred to as the “bad cholesterol.” High-density lipoproteins (HDL) take the extra cholesterol from your blood vessels and cells and return it to your liver for repurposing or for removal from the body. That Is why HDL is called the “good cholesterol.”
If there are not enough HDLs to remove the excess LDLs from the body, there is more of a likelihood that plaque, a hardened mixture of cholesterol, fat, and other elements, will develop in the arteries. This buildup can eventually lead to arterial blockage and an increased risk for heart disease and stroke. Plaque build-up happens over time, and as you age, the risk of problems from plaque increases. Long before they can be called plaques, hints of cholesterol build-up can be found in the arteries. Even some adolescents have these “fatty streaks” of cholesterol in their artery walls. These streaks are early precursors of cholesterol plaques.
The disease known as atherosclerosis, where plaque build-up damages blood vessels, is caused by high cholesterol damaging the blood vessel walls, creating a place for cholesterol to enter into the wall. LDL circulating in the blood accumulates in the blood vessel walls, and over the years, plaque formation occurs. Plaque can cause a narrowing and a hardening at the site of the blockages. Blood has much more difficulty making it through the damaged blood vesels. This damage often occurs in the blood vessels that supply blood to the heart. Often plaque can break loose from the blood vessel walls, and when this happens, the body will try to heal the damage caused by the break in the wall. The body does this by building a clot in the area of the damage. These clots, if they block a major blood vessel which supplies blood to the heart or to the brain can cause heart attacks and strokes. HDL’s are vital in lowering the risk of heart attacks and strokes by ridding the blood vessels of excess LDLs.
High cholesterol can also create an imbalance of bile acids, leading to gallstones. More than 80 per cent of gallstones are cholesterol stones. High cholesterol can also interfere with blood flow to your arms and legs. Numbness and pain are a result of decreased blood flow. There is also a greater risk of infection in these limbs. Lack of blood can eventually result in tissue death, a condition known as gangrene.
For these reasons, the levels of LDL and HDL are vital. For optimum health, the LDL concentration should be below a certain level, and the HDL level should be higher than a certain level. In this scenario, there is less chance of a build-up of plaque (low LDL), and higher removal of excess cholesterol from the body (high HDL). Your doctor will let you know if the levels of LDL and HDL cholesterol you have are within healthy levels or whether they are abnormal.
Genetics can play a significant role in the levels of cholesterol in the body. Some people’s bodies are better at self-regulation than others. If they consume too much cholesterol from their diet, their bodies will produce less cholesterol and their levels stay within normal limits. However, with other people who ingest too much cholesterol, their bodies do not slow down its own production of cholesterol, which leads to levels that can endanger health.
Cholesterol is both our friend and foe, hence the “good” and the “bad”. At normal levels, it is an essential substance for the body’s normal functioning, but if levels in the blood get too high, it becomes a silent danger that puts us at a higher risk of death from various diseases.
Next month we will learn what can increase cholesterol levels in our body, and strategies that we can take to maintain the cholesterol in our bodies at a healthy level.