Cholesterol is a waxy, fat-like substance that is made in the body by the liver. Cholesterol forms part of every cell in the body and serves a number of vital functions.

The heart pumps blood through blood vessels called arteries. This blood carries vital oxygen and nutrients needed by tissues and organs throughout the body. The heart itself is supplied with blood vessels called coronary arteries. When cholesterol levels rise above normal limits and stay high, some cholesterol is left behind in the arteries. Over the years, a hardened, waxy substance called cholesterol plaque builds up on the artery walls, and reduces or blocks blood flow. Organs supplied by these arteries then become damaged because they cannot get the oxygen and nutrients they need. For example, when blood flow to the brain is blocked, a stroke occurs. When plaque completely blocks a coronary artery, a heart attack takes place.

Cholesterol in the body comes from two sources. Most cholesterol is made by the liver from various nutrients and especially from saturated fats. The liver makes just about all the cholesterol the body will ever need. Since all animals can make their own cholesterol, some cholesterol in the human body comes directly from eating animal products. These foods include meats, egg yolks, organ meats, whole milk and milk products. This cholesterol is absorbed through the intestines and added to what the liver makes. It is also known that a diet high in saturated fat seems to increase cholesterol production in the body. Therefore, reducing dietary cholesterol and fats helps to keep blood cholesterol levels within a healthy range.

Our body does need cholesterol to make bile salts, hormones and vitamin D. It is mainly produced by our liver. Cholesterol will build up on the artery walls when the level of cholesterol in the blood is too high. There are 2 main types of blood cholesterol: LDL (the "Bad" cholesterol) and HDL (the "Good" cholesterol).

High amounts of the bad LDL will deposit cholesterol on the artery walls forming plaques. More and more plaques will narrow the arteries lumen and may eventually block blood flow. Therefore LDL is considered the "Bad" cholesterol. Saturated fats and trans fattty acids are the most important factors that raise blood cholesterol, not dietary cholesterol! Monounsaturated fats and polyunsaturated fats found in nuts and fish for instance, can lower the LDL level. In addition, soluble fiber found in fruits, oats, barley and legumes can also lower LDL.

The good HDL, on the other hand, takes excess cholesterol away and carries it back to the liver to be excreted. It can also remove some of the cholesterol already attached to the artery walls. Therefore HDL is considered the "Good" cholesterol as high levels of HDL in the blood can decrease the risk of heart disease. Physical activity can also raise HDL level.

Fortunately, most people can bring down their blood cholesterol levels without medication by changing their diet and by becoming more active. It's worth remembering that for every 1 percent you lower your blood cholesterol level, you reduce your risk for heart disease by 2 percent. Furthermore, lowering cholesterol can help prevent heart attacks even if you already have heart disease.

High and Low Cholesterol Levels
Risk for heart disease and stroke increases with rising blood cholesterol levels. As blood cholesterol exceeds 220 ml/dl (milligrams per deciliter-the units used to measure blood cholesterol in the United States), risk for heart disease increases at a more rapid rate.

If your blood cholesterol level is:

• Below 180 - your blood cholesterol level is ideal.
• 180-199 - your blood cholesterol level is acceptable.
• 200-219 - your blood cholesterol level is borderline high.
• 220 or higher - your blood cholesterol level is too high

If your total blood cholesterol level is greater than 200 (and especially if it is over 220), you should have another test to determine the individual levels of LDL cholesterol, HDL cholesterol and triglycerides.

Cholesterol & Diet: Eating too much saturated dietary fat (the kind found in high-fat meats and dairy products) and cholesterol can cause your body to make more cholesterol, raising your blood cholesterol levels. You can lower your cholesterol level by switching to a lower-fat diet thus reducing intake of animal fat and other fats and eating foods rich in starch and fiber, such as fresh fruits, vegetables, and whole grains.

Cholesterol & Exercise: Regular exercise not only reduces total blood cholesterol, but it lowers the bad kind of cholesterol (LDL cholesterol) while raising the good kind of cholesterol (HDL cholesterol). With improved diet, exercise helps to reduce weight/obesity, another cholesterol-risk factor.

Cholesterol & Weight/Obesity: Being overweight contributes to rising blood cholesterol levels. Conversely, following an effective weight loss diet and losing weight can help reduce cholesterol levels.

Cholesterol, Smoking & Hormones: Smoking is an important risk-factor for raised blood cholesterol levels and heart disease. Meanwhile, women get a natural boost in their HDL cholesterol (the good kind of cholesterol) from their hormones until they reach menopause. After menopause, taking estrogen can help maintain higher HDL cholesterol levels.