Many people think of dietary cholesterol when they hear the word cholesterol, and most people are aware that they should not consume too much. However, cholesterol plays many vital roles in the human body's functions. Every human and animal cell contains cholesterol. In addition to the cholesterol you consume from eating animal-based foods, cholesterol is made within your body.
Sources
Cholesterol is a type of sterol--a class of lipid molecules--that is found in products of animal origin such as meats and dairy products. Plant-based foods do not contain cholesterol even if they are high in fat. Cholesterol also can be produced by your liver, so it is not essential to consume dietary cholesterol.
Uses
More than 90 percent of the body's cholesterol is contained in the cell membranes, according to M.B. Grosvenor and L.A. Smolin in their book "Nutrition: Everyday Choices." Cholesterol is also found in myelin, which surrounds your nerves. Your body uses cholesterol to process vitamin D, which is used to make the bile acids that help you digest fats. Your body also uses cholesterol to make hormones such as testosterone and estrogen.
Cholesterol and Lipoproteins
The fats that are eaten do not dissolve in water, which is the main component of blood. Therefore, fats need molecules to carry them throughout the bloodstream until they travel to the muscles for energy or to the fat cells for storage.
Chylomicrons, very low density lipoproteins (VLDL), low density lipoproteins (LDL) and high density lipoproteins (HDL) are all types of lipoproteins that transport fats and cholesterol throughout the body. Because these lipoproteins carry fats and cholesterol throughout the body, each lipoprotein contains some amount of cholesterol.
HDL is known as good cholesterol and LDL is known as bad cholesterol. However, neither one is good or bad. All of these lipoproteins are needed by your body.
Chylomicrons absorb fat from the intestinal lining. They bring fats to your body's cells on their way to your liver. VLDLs leave your liver to transport lipids throughout your body. LDLs have a higher concentration of cholesterol in them than chylomicrons or VLDL. LDLs distribute cholesterol to your body's cells. HDLs collect cholesterol from your body's cells to return it to the liver, which then removes some of the cholesterol from your bloodstream.
Cholesterol Buildup
Diets high in cholesterol, saturated fats and trans fats are correlated with higher rates of heart disease, according to the "New Harvard Guide to Women's Health." If the amount of LDL cholesterol in your blood exceeds the amount taken up by your body's cells, the extra LDL tends to deposit and build up on artery walls. Atherosclerosis is a narrowing of the arteries due to the buildup of these fatty deposits and scar tissue. These protrusions into the arteries may eventually cause a blood clot to form, which can lead to a heart attack or stroke.
Warning
Per the recommendations of the National Cholesterol Education Program of the National Institutes of Health, a cholesterol level of 200 mg/dL (milligrams per deciliter) or less is normal, 200 to 239 mg/dL is borderline high, and over 240 is high. For people without known coronary artery disease, LDL levels under 130 mg/dL are considered normal, 130 to 159 mg/dL is considered borderline high and levels over 160 mg/dL are high. If you have high or borderline high cholesterol levels, limit fat intake to 30 percent or fewer of your daily calories and limit cholesterol intake to 300 mg per day or less. If your cholesterol or LDL levels are high, seek advice from your physician.
References
- "Nutrition: Everyday Choices;" Grosvenor, M. B., and Smolin, L. A.; 2006
- "New Harvard Guide to Women's Health;" President and Fellows of Harvard College; 2004
- National Cholesterol Education Program: ATP III At-A-Glance
