Why Are Cholesterol And Triglyceride Levels So Important?
Wherever you go, be sure to watch your cholesterol and triglyceride levels. Cholesterol and triglycerides are the two forms of lipids, or fats that circulate in the bloodstream. Both are necessary for life itself.
Cholesterol builds and maintains the basic building blocks of cells, such as cell membranes, and is necessary for the production of several important hormones, including estrogen, progesterone, vitamin D and steroids. Triglycerides are a high-energy chain of fatty acids that provide most of the energy needed for tissue function. You can’t live without these two types of fat.1.
But if your blood cholesterol and triglyceride levels are too high, your risk of heart attack, stroke and peripheral vascular disease is greatly increased. So you need to watch your blood lipid levels.
The big picture
There are two sources of cholesterol and triglycerides: dietary sources and “endogenous” sources (produced by the body). Dietary cholesterol and triglycerides are produced primarily by the consumption of meat and dairy products. These dietary fats are absorbed by the intestine and transported by the blood to the liver, where they are processed.
3 One of the main jobs of the liver is to ensure that all the cholesterol and triglycerides needed by the body’s tissues are extracted. Generally, about 8 hours after a meal, the liver absorbs dietary cholesterol and triglycerides from the blood. When dietary fat is lacking, the liver itself produces cholesterol and triglycerides. In fact, about 75% of the cholesterol in the body is produced by the liver.
The liver releases cholesterol and triglycerides, as well as special proteins, into the circulation in small globular packages called lipoproteins. Cholesterol and triglycerides are removed from the lipoproteins and sent to the cells in the body that need them.
Excess triglycerides – those not needed immediately as fuel – are stored in fat cells for later use. It is important to understand that most of the fatty acids stored in the body come from dietary carbohydrates. Since our bodies can only store a limited amount of carbohydrates, the “extra” carbohydrates we eat are converted to fatty acids, packaged as triglycerides, and stored as fat (which explains why we can easily become obese even on a low-fat diet). The stored fatty acids are separated from the triglycerides and burned as fuel during fasting.
Good and bad cholesterol
You’ll often hear doctors and nutritionists talk about two different “types” of cholesterol: low-density lipoprotein (LDL) cholesterol (“bad” cholesterol) and high-density lipoprotein (HDL) cholesterol (or “good” cholesterol). This way of talking about cholesterol is a convenient shorthand, but it is not strictly correct.
Strictly speaking, as any good chemist will tell you, cholesterol is cholesterol. One molecule of cholesterol is about the same size as any other molecule. So, why do doctors talk about good cholesterol and bad cholesterol?
The answer is lipoproteins
Lipoproteins. Because cholesterol (and triglycerides) are lipids, they do not dissolve in an aqueous medium like blood. In order for the lipids not to clump in the blood, they must be packaged into tiny particles called lipoproteins. Lipoproteins are readily soluble in the blood, making it easier for cholesterol and triglycerides to enter the bloodstream.
The “behavior” of various lipoproteins is determined by the presence of specific types of proteins (called apolipoproteins) on their surfaces. The metabolism of lipoproteins is very complex and scientists are still working on all the details.
However, most doctors are concerned with two major groups of lipoproteins, LDL and HDL.
LDL cholesterol – the “bad” cholesterol. In most people’s blood, most of the cholesterol is concentrated in the LDL particles, and LDL cholesterol is often referred to as the “bad” cholesterol.
High levels of LDL cholesterol are strongly associated with an increased risk of heart attack and stroke. Many experts believe that when LDL cholesterol levels are too high, LDL tends to adhere to the lining of blood vessels and promotes atherosclerosis. Thus, high LDL cholesterol is a major risk factor for heart disease and stroke.
7 While there is no doubt that high LDL cholesterol is a major contributor to heart risk, in recent years experts have begun to question whether lowering LDL cholesterol by itself necessarily reduces risk. Specifically, lowering LDL cholesterol with statins significantly reduces heart risk, but lowering LDL cholesterol with most other types of drugs has not been conclusively proven. Current cholesterol treatment guidelines rely heavily on the use of statins because these drugs not only lower cholesterol, but also help stabilize plaque and have potential anti-inflammatory effects.
HDL cholesterol – the “good” cholesterol. A high level of HDL cholesterol in the blood is associated with a low risk of heart disease, while a low level of HDL cholesterol is associated with a high risk. That’s why HDL cholesterol is often referred to as “good” cholesterol.
It appears that HDL “cleans” the walls of blood vessels and removes excess cholesterol. Thus, HDL cholesterol is, roughly speaking, the excess cholesterol that has just been removed from the cells and blood vessel walls and recycled back into the liver, and the higher the HDL cholesterol level, the more cholesterol is removed to areas that may be damaged. The higher the level of HDL cholesterol, the more cholesterol is removed to more vulnerable sites.
The idea that HDL cholesterol is always “good” cholesterol has been questioned in recent years, but it seems that the truth is actually a bit more complicated than the simple fact that HDL = good cholesterol. For example, pharmaceutical companies have scrambled to design drugs to raise HDL levels, but so far have hit a wall: many of the drugs that have successfully raised HDL levels have failed to improve heart disease outcomes. These results have forced experts to rethink their thinking about HDL cholesterol.
High levels of LDL cholesterol and triglycerides are strongly associated with a high risk of cardiovascular disease. While there is some controversy over the fact that high cholesterol and triglycerides themselves directly contribute to heart disease, the fact is that if you have a high cardiovascular risk, you need to reduce it, and if you take steps to reduce abnormal lipid levels, you will reduce your heart risk. In order to reduce your personal risk, you need to focus on taking steps that work.