Cholesterol is a lipid (fat), which is produced by the liver. Cholesterol is vital for normal body function. Every cell in our body has cholesterol in its outer layer.
Cholesterol is a waxy steroid and is transported in the
blood plasma of all animals. It is the main sterol synthesized by animals -
small amounts are also synthesized in plants and fungi. A sterol is a steroid
sub-group.
Cholesterol levels among US adults today are generally higher than in all other industrial nations. During the 1990s there was some concern about cholesterol levels in American children. According to the CDC (Centers for Disease Control and Prevention), nearly 1 in every 10 children/adolescents in the USA has elevated total cholesterol levels; and this was after concentrations had dropped over a 20-year period.
The word "cholesterol" comes from the Greek word chole, meaning "bile", and the Greek wordstereos, meaning "solid, stiff".
What are the functions of cholesterol?
- It builds and maintains cell membranes (outer layer), it prevents crystallization of hydrocarbons in the membrane
- It is essential for determining which molecules can pass into the cell and which cannot (cell membrane permeability)
- It is involved in the production of sex hormones (androgens and estrogens)
- It is essential for the production of hormones released by the adrenal glands (cortisol, corticosterone, aldosterone, and others)
- It aids in the production of bile
- It converts sunshine to vitamin D. Scientists from the Rockefeller University were surprised to find that taking vitamin D supplements do not seem to reduce the risk of cholesterol-related cardiovascular disease.
- It is important for the metabolism of fat soluble vitamins, including vitamins A, D, E, and K
- It insulates nerve fibers
There are three main types of lipoproteins
Cholesterol
is carried in the blood by molecules called lipoproteins. A lipoprotein is any
complex or compound containing both lipid (fat) and protein. The three main
types are:
LDL (low density lipoprotein) - people
often refer to it as bad
cholesterol. LDL carries cholesterol from the liver to cells. If too much
is carried, too much for the cells to use, there can be a harmful buildup of
LDL. This lipoprotein can increase the risk of arterial disease if levels rise
too high. Most human blood contains approximately 70% LDL - this may vary,
depending on the person.
HDL (high density lipoprotein) - people
often refer to it as good
cholesterol. Experts say HDL prevents arterial disease. HDL does the
opposite of LDL - HDL takes the cholesterol away from the cells and back to the
liver. In the liver it is either broken down or expelled from the body as
waste.
Triglycerides - these
are the chemical forms in which most fat exists in the body, as well as in
food. They are present in blood plasma. Triglycerides, in association with
cholesterol, form the plasma lipids (blood fat). Triglycerides in plasma
originate either from fats in our food, or are made in the body from other
energy sources, such as carbohydrates. Calories we
consume but are not used immediately by our tissues are converted into
triglycerides and stored in fat cells. When your body needs energy and there is
no food as an energy source, triglycerides will be released from fat cells and
used as energy - hormones control this process.
What are normal cholesterol levels?
The amount of
cholesterol in human blood can vary from 3.6 mmol/liter to 7.8 mmol/liter. The
National Health Service (NHS), UK, says that any reading over 6 mmol/liter is
high, and will significantly raise the risk of arterial disease. The UK
Department of Health recommends a target cholesterol level of under 5
mmo/liter. Unfortunately, two-thirds of all UK adults have a total cholesterol
level of at least five (average men 5.5, average women 5.6).
Below is a list of cholesterol levels and how most doctors would categorize them in mg/dl (milligrams/deciliter) and 5mmol/liter (millimoles/liter).
Below is a list of cholesterol levels and how most doctors would categorize them in mg/dl (milligrams/deciliter) and 5mmol/liter (millimoles/liter).
- Desirable - Less than 200 mg/dL
- Bordeline high - 200 to 239 mg/dL
- High - 240 mg/dL and above
- Optimum level: less than 5mmol/liter
- Mildly high cholesterol level: between 5 to 6.4mmol/liter
- Moderately high cholesterol level: between 6.5 to 7.8mmol/liter
- Very high cholesterol level: above 7.8mmol/liter
Dangers of high cholesterol levels
High cholesterol levels can cause:
- Atherosclerosis - narrowing of the arteries.
- Higher coronary heart disease risk - an abnormality of the arteries that supply blood and oxygen to the heart.
- Heart attack - occurs when the supply of blood and oxygen to an area of heart muscle is blocked, usually by a clot in a coronary artery. This causes your heart muscle to die.
- Angina - chest pain or discomfort that occurs when your heart muscle does not get enough blood.
- Other cardiovascular conditions - diseases of the heart and blood vessels.
- Stroke and mini-stroke - occurs when a blood clot blocks an artery or vein, interrupting the flow to an area of the brain. Can also occur when a blood vessel breaks. Brain cells begin to die.
If both blood cholesterol and triglyceride levels are high,
the risk of developing coronary heart disease rises significantly.
Symptoms of high cholesterol
(hyper-cholesterolaemia)
Symptoms of high cholesterol do not exist alone in a way a
patient or doctor can identify by touch or sight. Symptoms of high cholesterol
are revealed if you have the symptoms of atherosclerosis, a
common consequence of having high cholesterol levels. These can include:
- Narrowed coronary arteries in the heart (angina)
- Leg pain when exercising - this is because the arteries that supply the legs have narrowed.
- Blood clots and ruptured blood vessels - these can cause a stroke or TIA (mini-stroke).
- Ruptured plaques - this can lead to coronary thrombosis (a clot forming in one of the arteries that delivers blood to the heart). If this causes significant damage to heart muscle it could cause heart failure.
- Xanthomas - thick yellow patches on the skin, especially around the eyes. They are, in fact, deposits of cholesterol. This is commonly seen among people who have inherited high cholesterol susceptibility (familial or inherited hyper-cholesterolaemia).
What causes high cholesterol?
Lifestyle causes
- Nutrition - although some foods contain cholesterol, such as eggs, kidneys, eggs and some sea foods, dietary cholesterol does not have much of an impact in human blood cholesterol levels. However, saturated fats do! Foods high in saturated fats include red meat, some pies, sausages, hard cheese, lard, pastry, cakes, most biscuits, and cream (there are many more).
- Sedentary lifestyle - people who do not exercise and spend most of their time sitting/lying down have significantly higher levels of LDL (bad cholesterol) and lower levels of HDL (good cholesterol).
- Bodyweight - people who are overweight/obese are much more likely to have higher LDL levels and lower HDL levels, compared to people who are of normal weight.
- Smoking - this can have quite a considerable effect on LDL levels.
- Alcohol - people who consume too much alcohol regularly, generally have much higher levels of LDL and much lower levels of HDL, compared to people who abstain or those who drink in moderation.
Treatable medical conditions
These medical conditions are known to cause LDL levels to rise. They are all conditions which can be controlled medically (with the help of your doctor, they do not need to be contributory factors):
·
Diabetes
·
High blood
pressure (hyper-tension)
·
High levels of triglycerides
·
Kidney diseases
·
Liver diseases
·
Under-active thyroid gland
Risk factors which cannot be treated
These are known as fixed risk factors:
These are known as fixed risk factors:
·
Your genes 1 - people with close
family members who have had either a coronary heart disease or a stroke, have a
greater risk of high blood cholesterol levels. The link has been identified if
your father/brother was under 55, and/or your mother/sister was under 65 when
they had coronary heart disease or a stroke.
·
Your genes 2 - if you have/had a
brother, sister, or parent with hyper-cholesterolemia (high cholesterol) or
hyper-lipidemia (high blood lipids), your chances of having high cholesterol
levels are greater.
·
Your sex - men have a greater
chance of having high blood cholesterol levels than women.
·
Your age - as you get older
your chances of developing atherosclerosis increase.
·
Early menopause - women whose menopause occurs early are more susceptible to
higher cholesterol levels, compared to other women.
·
Certain ethnic groups - people from the Indian sub-continent (Pakistan,
Bangladesh, India, Sri Lanka) are more susceptible to having higher cholesterol
levels, compared to other people.
How is high cholesterol diagnosed?
Blood and cholesterol screening results
Cholesterol levels may be measured by means of a simple blood
test. It is important not to eat anything for at least 12 hours before the
blood sample is taken. The blood sample can be obtained with a syringe, or just
by pricking the patient's finger.
The blood sample will be tested for LDL and HDL
levels, as well as blood triglyceride levels. The units are measure in mg/dl
(milligrams/deciliter) or 5mmol/liter (millimoles/liter).
Researchers at the Sree Sastha Institute of
Engineering and Technology, India, developed a photographic cholesterol
test, which they describe as a completely non-invasive way to
test cholesterol levels.
People who have risk factors should consider
having their cholesterol levels checked.
What are the treatments for high cholesterol?
Lifestyle
Most people, especially those whose only risk factor has been lifestyle, can generally get their cholesterol and triglyceride levels back to normal by:
Most people, especially those whose only risk factor has been lifestyle, can generally get their cholesterol and triglyceride levels back to normal by:
- Doing plenty of exercise (check with your doctor)
- Eating plenty of fruits, vegetables, whole grains, oats, good quality fats
- Avoiding foods with saturated fats
- Getting plenty of sleep (8 hours each night)
- Bringing your bodyweight back to normal
- Avoiding alcohol
- Stopping smoking
Many experts say that people who are at high risk of
developing cardiovascular disease will not lower their risk just by altering
their diet. Nevertheless, a healthy diet will have numerous health benefits.
Cholesterol-Controlling Medications
If your cholesterol levels are still high after
doing everything mentioned above, your doctor may prescribe a
cholesterol-lowering drug. They may include the following:
- Statins (HMG-CoA reductase inhibitors) - these block an enzyme in your liver that produces cholesterol. The aim here is to reduce your cholesterol levels to under 4 mmol/liter and under 2 mmol/liter for your LDL. Statins are useful for the treatment and prevention of atherosclerosis. Side effects can include constipation, headaches, abdominal pain, and diarrhea. Atorvastatin, fluvastatin, lovastatin, pravastatin,rosuvastatin and simvastatin are examples of statins.
- Aspirin - this should not be given to patients under 16 years of age.
- Drugs to lower triglyceride levels - these are fibric acid derivatives and include gemfibrozil, fenofibrate and clofibrate.
- Niacin - this is a B vitamin that exists in various foods. You can only get very high doses with a doctor's prescription. Niacin brings down both LDL and HDL levels. Side effects might include itching, headaches, hot flashes (UK: flushes), and tingling (mostly very mild if they do occur).
- Anti hypertensive drugs - if you have high blood pressure your doctor may prescribe Angiotensin-converting enzyme (ACE) inhibitors, Angiotensin || receptor blockers (ARBs), Diuretics, Beta-blockers, Calcium channel blockers.
In some cases cholesterol absorption inhibitors (ezetimibe)
and bile-acid sequestrants may be prescribed. They have more side effects and
require considerable patient education to achieve compliance (to make sure
drugs are taken according to instruction).
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Source:- Various
SutharyA Health Cares,
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