Bodies in Motion: Cholesterol
We’ve been told for years that we must lower our cholesterol levels to reduce the risk of heart disease. In the past, this included advice to drastically reduce your intake of dietary cholesterol and saturated fat. But emerging evidence suggests that dietary sources may play less of a role than previously believed. Trans fats are one exception. These artificial fatty acids, found in some packaged baked goods and margarines, are known to alter blood lipid levels in a way that is detrimental to cardiovascular health. They should be avoided. In this interactive experience, you’ll learn more about the complex nature of cholesterol in the body, its role in supporting health—and in potentially fostering heart disease.
The Different Types of Cholesterol
The body makes cholesterol in the liver and uses it for a variety of important functions, ranging from maintaining healthy cell membranes to building crucial hormones and vitamins. Cholesterol is a waxy substance that does not mix with water. To facilitate its transportation through the bloodstream, it is packaged into tiny protein-coated particles. These cholesterol-encased packages are called lipoproteins.
LDL (low density lipoprotein) is one such lipoprotein. Another is HDL (high density lipoprotein). These two very different forms of cholesterol play essentially opposing roles in the body. LDL, featuring more fat and less protein, delivers cholesterol wherever it’s needed. HDL, consisting of more protein and less fat, actually helps remove excess cholesterol particles from the bloodstream. This is why HDL is often called “good”: It helps reduce the amount of circulating cholesterol, which might otherwise stick to blood vessel walls and develop into plaques that can impede blood flow and clog arteries. If allowed to progress, these plaques can eventually lead to heart attack or stroke.
The Role of LDL or Bad Cholesterol
LDL is often referred to as “bad” cholesterol, due to its role in promoting cardiovascular disease. But this nickname is an oversimplification. It ignores cholesterol’s beneficial roles in the body. In reality, cholesterol is an important building block the body uses to generate or maintain a variety of tissues and important substances. The body harnesses the energy of sunlight striking bare skin, for example, to convert a cholesterol-based compound into a substance that ultimately becomes vitamin D.
Similarly, cholesterol is an important component of cell membranes. Its role in the proper development of the brain and nervous system is so crucial that most of the cholesterol needed for this purpose is generated directly in the brain. Cholesterol is also used to make a number of important hormones, such as testosterone and various forms of estrogen. These hormones regulate everything from metabolism to inflammation and immune function. Blood levels of about 90 mg/dL of LDL-cholesterol are ideal. It’s only when LDL levels approach 200 mg/dL or more that LDL behaves “badly”.
The Role of HDL or Good Cholesterol
High-density lipoprotein (HDL), often dubbed “good” cholesterol, travels throughout the bloodstream mopping up stray cholesterol particles leftover from the process of building and maintaining cell membranes. This excess cholesterol is transported by HDL to the liver, where it is deposited for recycling. This helps keep blood cholesterol levels in check, and ensures that adequate levels of this important substance will be available to the body.
HDL also helps remove excess cholesterol that may otherwise contribute to the formation of plaques on blood vessel walls. These plaques are the underlying cause of atherosclerosis, and ultimately, most heart disease. HDL helps reduce the size of existing plaque formations. For this reason, high levels of HDL are considered beneficial. When assessing your relative risk of heart disease, your doctor looks at the ratio of LDL and HDL-cholesterol circulating in the bloodstream, among other factors. HDL of 60 mg/dL or more is considered high. Less than 40 mg/dL of HDL-cholesterol is considered low.
How the Body Produces Cholesterol
Cholesterol is a vital substance the body needs to build and maintain numerous tissues and substances. For this reason, the body is capable of producing the majority of the supply of this fatty substance that it needs. About three-fourths of the cholesterol in your body is produced within the liver.
The growing brain is also capable of producing cholesterol to fulfill its needs. The remainder is extracted from dietary sources after digestion, by absorption through the tissues of the small intestine. Foods that contain dietary cholesterol include red meat, seafood, eggs, poultry, fish and shellfish.
Medications to Manage Cholesterol
As we’ve seen, controlling cholesterol levels through diet alone can be difficult, since a majority of cholesterol in the body is manufactured in the liver. Several factors can affect cholesterol levels. These include the intake of plant foods featuring cholesterol-like substances called stanols and sterols. These natural compounds are thought to compete with dietary cholesterol for absorption by the intestines. Other foods, such as oat bran, have been shown to help lower LDL-cholesterol levels. HDL-cholesterol is known to increase in response to exercise.
But many people may require treatment with cholesterol-lowering drugs to reach target levels. Several options exist. Selective cholesterol absorption inhibitors work to prevent the uptake of cholesterol in the intestines. Bile acid sequestrants are another option. They help lower cholesterol by interfering with the recycling of bile acids, which are cholesterol-containing components of the digestive system. Sometimes, doctors prescribe supplements, such as the B-vitamin, niacin, to help raise levels of HDL-cholesterol.
Modern statin drugs are perhaps the most popular medications prescribed to lower LDL-cholesterol levels. Some of these drugs also favorably impact HDL levels. They work by interfering with an enzyme the body uses to generate new cholesterol. They may also help with the resorption of cholesterol in plaques along blood vessel walls. Combination statins are drugs that combine the cholesterol-lowering power of a statin with a bile acid sequestrant, or a cholesterol absorption inhibitor, to reduce the amount of cholesterol circulating in the form of bile. By modifying the amounts and types of cholesterol in the body, it’s possible to significantly reduce the risk of cardiovascular disease.
How to Manage Your Cholesterol
Now that you know what cholesterol does in your body, the next step is going back to your charts (or your doctor) and looking at your own numbers. Figure out where you stand—where you are doing well, and where you can improve.
Then take the next step: make a concentrated effort to eat better, exercise more, and stay motivated to lower your cholesterol. By doing so, you'll add years to your life.