Cholesterol Functions, Dangers, Blood Test Results and Control

Cholesterol is a very important chemical in the human body and has many essential functions. Our bodies make all of the cholesterol that we need, however. If we eat certain foods or follow certain lifestyles, the amount of cholesterol in the body may increase and cause health problems. Diet and lifestyle changes can help return body cholesterol to a healthy level.

Essential Functions in the Cell Membrane

Cells are surrounded by a cell membrane which controls what substances get into and out of the cell. Cell membranes require cholesterol in order to function properly. The cholesterol maintains the correct fluidity of the membrane at different temperatures, increasing the fluidity at low temperatures and decreasing it at high temperatures. Cholesterol also reduces the permeability of the membrane to certain substances.

Improving Nervous System Function

A neuron (nerve cell) has an extension called an axon. The axon transmits nerve impulses to the next neuron. The myelin sheath is a covering that surrounds and electrically insulates axons. This insulation speeds up the transmission of nerve impulses. Myelin contains a large concentration of lipids, including cholesterol.

Hormone Production

Cholesterol is a steroid molecule and is converted to steroid hormones in the body. These hormones include the reproductive hormones estrogen, progesterone and testosterone. Other steroid hormones made from cholesterol are cortisol and aldosterone. Cortisol has many functions in the body, including helping to regulate the blood sugar level. Aldosterone affects the amount of sodium ions and water in the body.

Vitamin D Production

Our skin makes a vitamin D precursor from 7-dehydrocholesterol when it absorbs ultraviolet light. This precursor is then converted to active vitamin D inside the body. Researchers are discovering that vitamin D has many very important functions in the body. The vitamin is needed for the absorption of calcium in the small intestine and also plays a role in immunity and cancer prevention.

Bile Acids and Salts

Bile is a yellow-green liquid made by the liver. Bile emulsifies fats in the small intestine, which prepares them for digestion by enzymes. The emulsification is performed by bile acids, which may exist in the form of bile salts. Bile acids are made from cholesterol.

Cholesterol is a type of lipid. Since lipids cannot dissolve in the watery blood plasma, cholesterol molecules are attached to lipoprotein molecules in order to be transported around the body in blood. A lipoprotein contains both lipid and protein.

LDL Cholesterol

LDL cholesterol is cholesterol attached to lipoproteins that have low density. This type of cholesterol is often called the “bad” cholesterol. Low-density lipoproteins transport cholesterol from the liver through the blood to the rest of the cells in the body. When there is too much LDL cholesterol in the blood, cholesterol collects in the lining of arteries. The cholesterol and other substances such as fat and calcium form a deposit called plaque, which may protrude into the channel of the artery.

The buildup of plaque in arteries is called atherosclerosis. Plaque can decrease the available space for blood flow and also increases the probability of blood clots. Bits of plaque can break off, leaving a rough surface which can cause a blood clot to develop. Blood clots and broken bits of plaque can move to other areas, blocking the flow of blood. These processes can cause a heart attack if they happen in a coronary artery, since the coronary arteries supply oxygen and nutrients to the heart muscle. Blockage of the carotid arteries going to the brain can cause a stroke. Blocked arteries in the arms and legs can result in peripheral artery disease (PAD), also called peripheral vascular disease. Peripheral artery disease affects the legs more commonly than the arms and can cause leg numbness and weakness. Plaque can also cause artery walls to become less flexible.

HDL Cholesterol

HDL cholesterol is cholesterol attached to lipoproteins that have high density. This type of cholesterol is known as the “good” cholesterol. Although some people assume that anything with the word “cholesterol” in its name must be bad, scientists have discovered that cholesterol attached to high-density lipoprotein is a good substance to have in our bodies, since it reduces the risk of heart disease. High-density lipoproteins transport cholesterol from the arteries to the liver, which processes it or eliminates it from the body.

There are several types of blood tests which can be used to measure the cholesterol level. One test determines the total cholesterol level. If this test shows that the cholesterol level is higher than it should be, more specific tests can be performed to discover the LDL cholesterol level and the HDL cholesterol level.

A lipid profile is a blood test that measures the level of total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides (neutral fats) and sometimes VLDL cholesterol (very low density lipoprotein cholesterol) as well. Like LDL cholesterol, VLDL cholesterol stimulates cholesterol to build up in the arteries. The normal blood level of VLDL cholesterol is between 5 and 40 mg/dL.

Sometimes the ratio of total cholesterol to HDL cholesterol is reported. The lower this ratio the better. A desirable ration is 4.0. A ratio of 5.0 is borderline and 6.0 is a high ratio.

In the United States cholesterol levels are measured in milligrams of cholesterol per deciliter of blood. In Canada and many countries in Europe the cholesterol levels are measured in miilimoles of cholesterol per liter of blood. The tables show the generally accepted meanings of different cholesterol levels. Women usually have a higher HDL cholesterol level than men. While men are said to have a low HDL cholesterol level at less than 40 mg/dL (1 mmol/L) , women have a low HDL cholesterol level at less than 50mg/dL (1.3 mmol/L).

Our body makes all the cholesterol that we need. If we obtain cholesterol from other sources, the liver reduces the amount of cholesterol that it makes. However, there is a limit to the liver’s ability to control the blood cholesterol level.

Fat and Cholesterol Level

To keep blood cholesterol at a healthy level, saturated fats should be restricted in the diet, since they have been found to increase the cholesterol level in the body. Saturated fats are found in foods that come from animals, such as fatty meats and full-fat dairy foods.

Eggs are low in saturated fat but high in cholesterol. Strangely, for most people, eating foods containing cholesterol doesn’t increase the blood cholesterol level significantly. Eggs are packed full of nutrients and are a great addition to the diet, except for people who have been diagnosed with an inherited form of hypercholesterolemia. In this disorder, which has a genetic basis, the blood cholesterol is abnormally high. Doctors advise people with hypercholesterolemia to avoid or limit foods containing cholesterol.

Fats in the diet should be mainly monounsaturated. Monounsaturated fats have been found to have a neutral or even beneficial effect on blood cholesterol. Olive oil is rich in monounsaturated fatty acids and lowers LDL cholesterol. The same is true for almonds. Walnuts, which contain mainly polyunsaturated fats, also lower LDL cholesterol. Remember not to eat too much fat, even is the fat is classified as healthy, and make sure that nuts are not salted or roasted in oil.

Artificial trans fats, which have been partially hydrogenated to change their properties, should be completely removed from the diet. They increase the bad LDL cholesterol and also decrease the good HDL cholesterol.

Soluble Fiber and Cholesterol Level

Soluble fiber has also been found to lower LDL cholesterol. Soluble fiber forms a gel when it mixes with water in the small intestine. There are several theories concerning how this gel lowers cholesterol. One theory is that the gel prevents the reabsorption of bile acids from the small intestine. Bile acids are usually reabsorbed once they have done their job. If they aren’t reabsorbed, they pass out of the body in the feces. The liver then has to convert more cholesterol into bile acids, thereby reducing the blood cholesterol level.

Grains containing high amounts of soluble fiber include oatmeal and barley. Vegetables containing significant amounts of soluble fiber include peas, beans, beets, parsnips, carrots, sweet potatoes and potatoes. Fruits can also be a good source of soluble fiber. Bananas, apples, pears, strawberries, plums, prunes and citrus fruits all rich in healthy soluble fiber.

Food Additives and Cholesterol Level

Some types of processed foods contain cholesterol-lowering additives. Plant sterols and stanols, which have been shown to decrease LDL cholesterol level, are added to certain types of orange juice and margarine, for example.

Other Foods Which Affect Cholesterol Level

While there is strong evidence that certain foods lower LDL cholesterol, the evidence that specific foods raise HDL cholesterol is less strong. Alcohol does increase HDL cholesterol, but excess alcohol consumption can cause other health problems. Some evidence suggests that cranberry juice, raw onions and omega-3 fats found in fish such as salmon and sardines can increase HDL cholesterol. Salmon is a heart-healthy food even without affecting HDL cholesterol, since it lowers the level of trigylcerides in the blood and is low in saturated fat.

Niacin, or nicotinic acid, is a type of B vitamin. Niacin lowers LDL cholesterol and significantly raises HDL cholesterol when taken at high doses. These doses can cause unpleasant and possibly dangerous side effects, so high-dose niacin should never be taken without a doctor’s supervision.

Lifestyle

Smoking should be avoided, since it decreases the level of HDL cholesterol. On the other hand, regular exercise increases the level of HDL cholesterol, and so does weight loss (if it’s necessary).

If you are diagnosed with high cholesterol there is a lot that you can do to improve your cholesterol profile . You may not even need to take cholesterol-lowering medications. You can reduce or remove harmful foods from your diet, add foods known to lower LDL cholesterol, add healthy foods that might raise HDL cholesterol, stop smoking and get regular exercise. Begin exercising slowly if you haven’t exercised for a long time. These techniques will help ensure that cholesterol stays a friend and never becomes a foe.