Cholesterol

Cholesterol

 Cholesterol is a waxy, fat like substance found in the walls of cells in all parts of the body, from the nervous system to the liver to the

heart. The body uses cholesterol to make hormones, bile acids, vitamin D, and other substances.

The body makes all the cholesterol it needs. Cholesterol circulates in the bloodstream but cannot travel by itself. As with oil and water, cholesterol (which is fatty) and blood (which is watery) do not mix. So cholesterol travels in packages called lipoprotein.which have fat (lipid) inside and protein outside.

Two main kinds of lipoproteins carry cholesterol in the blood:

■ Low density lipoprotein, or LDL, which also is called the “bad” cholesterol because it carries cholesterol to tissues, including the arteries. Most of the cholesterol in the blood is the LDL form. The higher the level of LDL cholesterol in the blood, the greater your risk for heart disease.

■ High density lipoprotein, or HDL, which also is called the “good” cholesterol because it takes cholesterol from tissues to the liver, which removes it from the body. A low level of HDL cholesterol increases your risk for heart disease.

To clear some misconceptions cholesterol is a fat like substance, but it's not a fat itself. Cholesterol has a different structure from fat and performs different functions in the human body. Some functions promote health; some don't. Because fat and cholesterol often appear together in foods of animal origin, and because their roles in health are so intertwined they're easily mixed up.

Like fat, cholesterol often gets a "bad rap," yet it's part of every body cell and of some hormones . As part of a body chemical called bile, it helps the body digest and absorb fat, too. With the help of sunlight, a form of cholesterol in your skin can change to vitamin D, a nutrient essential for bone building.

 However, too much cholesterol in the bloodstream is linked to heart disease.

As the LDLs deliver cholesterol and other lipids to the cells, each cell's surface has receptor systems specifically designed to bind with LDLS. Circulating LDLs in the bloodstream bind to these LDL receptors and are consumed. Once inside the cell, the LDL is taken apart and its cholesterol is released. In liver cells these receptor systems aid in controlling blood cholesterol levels as they bind the LDLS. A deficiency of these LDL binding mechanisms will leave a high quantity of cholesterol traveling in the bloodstream, which can lead to heart disease or atherosclerosis. Diets rich in saturated fats will prohibit the LDL receptors. Thus, LDL receptors are critical for regulating cholesterol levels. HDLS" High-density lipoproteins are responsible for carrying

cholesterol out of the bloodstream and into the liver, where it is either reused or removed from the body with bile. HDLs have a very large

protein composition coupled with low cholesterol content (20 to 30 percent) compared to the other lipoproteins. Hence, these high density lipoproteins are commonly good cholesterol. LDL/HDL function. LDLs carry cholesterol into cells for normal usage,

but LDLs can also deposit cholesterol into the walls of blood vessels, which can lead to harmful disease. HDLS scavenge excess cholesterol from the cells, tissues, and blood vessels and deliver these back to the liver, where these are either reused or excreted.

LDL/HDL and inflammation. LDLs carry lipids that are pro inflammatory and may contribute to heart disease. HDLs transport lipids that are anti-inflammatory and may reduce the occurrence of heart disease.

If there is too much cholesterol in the blood, some of the excess can become trapped in artery walls. Over time, this builds up and is

called plaque. The plaque can narrow vessels and make them less flexible, a condition called atherosclerosis or “hardening of the

arteries.” This process can happen to blood vessels anywhere in the body, including those of the heart, which are called the coronary arteries.

If the coronary arteries become partly blocked by plaque, then the blood may not be able to bring enough oxygen and nutrients to the

heart muscle. This can cause chest pain, or angina. Some cholesterol rich plaques are unstable they have a thin covering and can burst, releasing cholesterol and fat into the bloodstream. The release can cause a blood clot to form over the plaque, blocking blood flow through the artery—and causing a heart attack.

Fat calories should be limited to 20-35 percent of total calories with most fats coming from polyunsaturated and mono - unsaturated fats, such as those found in fish, nuts, and vegetable oils.

Consume fewer than 10 percent of calories from saturated fats. Some studies suggest that lowering the saturated tat content to less than 7 percent can further reduce the risk of heart disease.

Keep the consumption of trans fats (any food label that reads hydrogenated or partially hydrogenated oil) to a minimum, less than 1 percent of calories.

Think lean and low-fat when selecting meat, poultry, milk, and milk  products.

For all age groups, most fats should come from polyunsaturated and mono unsaturated fats such as fish, nuts, and vegetable oils are identifying Sources of Fat

The recommended cholesterol test is called a "lipoprotein profile." It measures the levels of total cholesterol (which includes the cholesterol in all lipoproteins), LDL, HDL, and triglycerides. The lipoprotein profile is done after a 9- to 12-hour fast. A small sample of blood is taken from your finger or arm. If you don't fast, you can still have your total cholesterol and HDL levels measured.

The levels are measured as milligrams of cholesterol per deciliter of blood, or mg/dL. Box 3 gives the classifications for total, LDL, and HDL cholesterol.