Believe it or not, cholesterol is very essential to maintain a healthy life.
Your body uses it to make vitamin D, cell membranes, sex hormones, bile, and nerve sheaths. These and other functions fall to serum cholesterol, a waxy, fatty like compound that circulates in the bloodstream. The liver manufactures about a gram of it each day, which is about as much the body requires.
Dietary cholesterol is the type consumed in foods—specifically, animal products. The body does not need this cholesterol, but anyone other than a strict vegetarian who excludes all animal products will consume varying amounts of it. Many factors—exercise, genetics, gender, and other components of the diet—influence how the human body processes dietary cholesterol; some people can consume large amounts but have normal blood cholesterol, while others eat very little but have high blood cholesterol.
Good vs. Bad Cholesterol
To travel through the bloodstream, cholesterol molecules attach themselves to lipid-carrying proteins, or lipoproteins. Two types of lipoproteins are the major transporters of cholesterol: low-density lipoproteins (LDLs) carrying two third of it; most of the remainder is attached to high-density lipoprotein (HDLs). LDLs tend to deposit cholesterol in the artery walls, leading to atherosclerosis and an increased risk of heart disease. In contrast, HDLs collect cholesterol from the artery walls and other tissues and take it to the liver to be metabolized and eliminated from the body. This is why LDLs are often called the “bad” cholesterol and HDLs the “good”.
When a doctor tests blood cholesterol levels, he/she first measures the total amount in a deciliter of blood; anything below 200 milligrams per decimal is considered desirable. If the total is more than 200 milligram, LDL and HDL levels should be measured individually. LDL levels should be below 130mg/dl; 130 to 159 is classified as borderline high, and anything over 160 is considered high risk for coronary artery disease and a heart attack. HDLs levels should be at least 45mg/dl, and the higher the better. In assessing cardiovascular risk, doctors calculate the LDL/HDL ratio by dividing the total cholesterol by the HDL figure.
How Diet Can Help
The National Cholesterol Education Program recommends dietary modifications for any person with total cholesterol over 200mg or with an LDL cholesterol level exceeding 130mg. Reducing intake of saturated fats has the greatest effect on lowering blood cholesterol levels. A diet that limits fat intake to 20 percent or less of total calories and restricts saturated fats to 7 percent or less can lower total blood cholesterol on average of 14 percent. Most people can significantly lower intake of saturated fats by cutting down on or eliminating fatty meats, whole milk and other dairy products, and baked goods such as cakes.
It isn’t just what you don’t eat that matters; consuming foods that have a cholesterol-lowering effect also helps. Oat bran and dried beans and peas are high in soluble fiber, which lowers cholesterol. The pectin in apples and other fruits also lowers cholesterol, as does, apparently, the soy protein found in tofu, tempeh, and soy milk.
Two or three servings a week of salmon, sardines, shrimp, lobster, and other cold-water fish or seafood are linked with a reduced risk of heart attacks and strokes. Initially, it was thought that omega-3 fatty acids in seafood reduced cardiovascular risk by lowering blood cholesterol levels; however, recent studies suggest that their benefits comes from interfering with blood clotting and from possible changes in the way the liver metabolizes other lipids.
At one time, increasing the intake of polyunsaturated fats—corn, cottonseed, sea flower, soy, and sunflower oils—was advocated to lower cholesterol, but more recent studies have found that these oils reduce the levels of the protective HDLs while having little effect on the harmful LDLs. In contrast, monosaturated fats found in canola and olive oils have the opposite effect, cutting LDLs without altering HDL levels.
The role of dietary cholesterol is still unclear; recent studies indicate it is not as potent in raising blood cholesterol as saturated fats are. Still, the American Heart Association recommends limiting dietary cholesterol intake to 300mg a day—the amount of 1 and a half egg yolks, 4 ounces of beef liver, or a combination of 2 cups of whole milk, a 6 ounce steak, and 1 cup of ice cream.
Increased exercise, weight loss, and stress reduction can all lower cholesterol or improve the LDL/HDL ratio. Women are protected from developing coronary artery disease during their reproductive years by estrogen, and new research indicates that postmenopausal hormone replacement extends this protection into old age.
Moderate intake of alcohol—defined as one ounce of ethanol a day for women and two for men—lowers the risk of heart attack, presumable because it raises HDL levels. If dietary and other lifestyle changes fail to reduce cholesterol, drugs may be prescribed.