What is Cholesterol?

Contributing Author: The Tortoise

You cannot live without cholesterol. It is present in your blood and every cell of your body, and your body needs it in order to function normally. It also needs it to make hormones, Vitamin D and bile for digestion. Known as a lipid, cholesterol is a fatty substance which comes from two sources: your body and your food. While cholesterol is produced in the liver for the body's needs, it is also present in food from animal sources, such as meat, poultry and full-fat dairy products. Eggs, offal and shellfish are also rich in cholesterol. Although your body can make all the cholesterol it needs, the liver produces more cholesterol when your diet is high in saturated and trans fats. The effects of excess cholesterol can cause serious health problems. Because cholesterol cannot dissolve in blood, it has to be carried to and from cells by carriers called lipoproteins. Lipoproteins are little packages are made of fat (lipid) on the inside and proteins on the outside, and there are two kinds: low-density lipoproteins (LDL), and high-density lipoproteins (HDL). In recent years, LDL has become regarded as 'bad' cholesterol, while HDL has been called the 'good' cholesterol. We are going to take a closer look at these types of cholesterol and their function in your body.

LDL Cholesterol
Low-density lipoprotein (LDL) carries cholesterol to the cells in your body which need it. If there is too much cholesterol for your cells to use, this excess cholesterol can build up in the artery walls, leading to plaque and disease of the arteries. Plaque is a thick, hard deposit that can clog arteries and make them less flexible, resulting in a condition called atherosclerosis. Plaque can also break open and cause blood clots. If a blood clot blocks an artery to either the brain or the heart, the result is a stroke or a heart attack. Therefore, too much LDL cholesterol is unhealthy, and LDL is known as 'bad' cholesterol for this reason. A diet high in saturated fat and trans fat raises LDL cholesterol. As a general guide, LDL levels should be 3 mmol/L or less for healthy adults, and 2 mmol/L or less for those at high risk.

HDL Cholesterol
High-density lipoprotein (HDL) carries cholesterol away from your cells and arteries back to your liver, where it is broken down and passed from the body. One-fourth to one-third of blood cholesterol is carried by HDL. Low levels of HDL cholesterol have been shown to increase the risk of heart disease, while healthy levels of HDL cholesterol may protect against cardiovascular disease. For these reasons, HDL is regarded as 'good' protective cholesterol, and higher levels are better. In general, HDL levels should be above 1 mmol/L. Lower levels can increase the risk of heart disease.

So Why Should You Lower Your Cholesterol?
There is strong evidence that high cholesterol increases the risk of:

• Artherosclerosis, or narrowing of the arteries from plaque buildup
• Heart attack
• Stroke
• Transient ischaemic attack (TIA), or a 'mini stroke'
• Peripheral arterial disease (PAD), or the narrowing of arteries supplying blood to the legs, from plaque buildup

What Causes High Cholesterol?
Many factors can play a part in causing high cholesterol. Lifestyle, underlying conditions and 'fixed' factors which cannot be changed, all contribute.

Lifestyle factors contributing to high cholesterol:

• An unhealthy diet, particularly one high in saturated fat and trans fats.
• Obesity. Being overweight can lead to higher levels of LDL cholesterol, and lower levels of HDL cholesterol.
• Lack of exercise or physical activity. This can increase your levels of LDL cholesterol.
• Smoking. Cigarettes contain a chemical called acrolein which stops HDL from carrying cholesterol from fatty deposits to the liver, which can lead to artherosclerosis.
• Drinking

Underlying conditions contributing to high cholesterol:

• Diabetes or high blood pressure
• Kidney disease
• Liver disease
• Hypothyroidism

Fixed factors contributing to high cholesterol:

• A family history of heart disease or stroke.
• An inherited condition called familial hypercholesterolaemia, which can cause high cholesterol in someone even if they eat healthily.
• A family history of a cholesterol-related condition, such as having a parent, brother or sister with familial hypercholesterolaemia.
• Age. The older you are, the greater the likelihood of artherosclerosis.
• Ethnicity. People of Indian, Pakistani, Bangladeshi and Sri Lankan descent are at increased risk of having a heart attack.
• Sex. Males are more likely to have heart attacks than females.

Consequently, lowering your cholesterol levels will reduce your risk of cardiovascular disease, and improve your health. High cholesterol is often known as the 'silent killer' because there can be little or no indication of it. It is important to get your cholesterol levels checked regularly, and to do as much as you can to keep your cholesterol at a healthy level. Here are 6 tips on how to lower your cholesterol:

1. Get expert advice. Your doctor can help you with a plan for a heart-healthy diet and exercise.
2. Eat healthily. Eat less saturated fat and trans fat. Increase your intake of fruit, vegetables, fish, nuts, seeds and fibre.
3. Give up smoking. Your HDL levels will improve as a direct result.
4. Exercise. Physical activity lowers bad cholesterol and raises good cholesterol.
5. Take your medications. If your doctor has prescribed medicine to lower your cholesterol, do not forget to take it.
6. Try supplements. Fish oil, krill oil, fibre and soy protein supplements can lower LDL cholesterol. Ask your doctor if supplements may help you.

Resources
About cholesterol, American Heart Association
Cholesterol - the silent killer, Heart UK
Good vs. Bad Cholesterol, American Heart Association
High cholesterol, National Health Service
The myth of dietary cholesterol, Heart UK
Tips to keep your cholesterol in check, WebMD
What is cholesterol?, National Heart, Lung & Blood Institute
What your cholesterol levels mean, American Heart Association

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