Cholesterol: The Good & The Bad

Dr. Kate Bishop |Chief Scientific Officer

Last updated: 29 Mar 2019


Before taking a home blood cholesterol test it’s best to understand why it is being tested, what is being measured and what this could mean for your health.

What is Cholesterol?

Cholesterol is a type of fat vital for normal healthy bodily function. It’s so important because it's a part of the cell membrane in every cell of your body,  it helps make vitamin D and steroid hormones and it's used to make bile which is produced continuously by the liver.

So it plays an important role in brain and nerve function, maintaining healthy bones, teeth and skin as well as helping you digest food. Cholesterol is mostly produced in your liver although a  small amount is absorbed from the food you eat.

Your blood contains cholesterol attached to two main types of lipoprotein. These are:

  • High Density Lipoprotein (HDL) - often known as “good cholesterol”
  • Low Density Lipoprotein (LDL) - usually called “bad cholesterol”

HDL’s role is to carry cholesterol away from the cells in your body back to the liver where it can be processed and removed as waste. As this is an important function for good health then higher levels of HDL are better.

The job of LDL is to carry cholesterol to the cells and tissues of your body which need it. However when there is too much cholesterol for your body to use it can then be deposited in your arteries. This can lead to artery disease. So although LDL is important, it is typically known as bad cholesterol and lower levels are better.

There are additional lipoproteins as well - Very Low Density Lipoproteins (VLDL) which mainly carry triglycerides, another type of blood fat, from your liver to the cells of your body. But it also plays help carry cholesterol too. So just like LDL, high levels are considered a bad thing.

Intermediate density lipoproteins (IDL) are smaller than VLDL - they also carry triglycerides from the liver and as these triglycerides are transferred to the cells the IDL are converted into LDL. So yes, high levels of IDL

The final known type of lipoprotein are chylomicrons, the largest and densest of all. Their job is to carry dietary cholesterol and triglycerides absorbed in your intestine.

 

 

Bottom line: these additional lipoproteins are less important when you take a blood cholesterol test, and the important thing is that the levels of HDL (Good Cholesterol) and LDL (Bad Cholesterol) are established and their relative levels (Cholesterol Ratio) is determined.


Why Is High Cholesterol Bad?

Having high cholesterol (Hypercholesterolemia) in itself doesn't normally cause you to have symptoms but there is a lot of evidence that it does increase your risk of multiple cardiovascular complications and disease.

As cholesterol collect on your artery walls, the blood flow to the rest of your body is restricted. This includes less blood flow to important organs like your heart and brain as well as increasing the risk of blood clots elsewhere.

As you might expect this can lead to severe medical problems including an increase in risk for:

  • Heart attacks

  • Strokes

  • Narrowing of artery walls (atherosclerosis)

  • Coronary heart disease which can lead to chest pains or angina

  • Various other cardiovascular diseases


 

What can cause high cholesterol?

There are many factors which contribute to increasing your cholesterol and many of them relate to your lifestyle. These may not surprise you as they are well known poor-health indicators but you should consider whether:

  • You have an unhealthy diet. Actually the latest evidence suggests that the amount of cholesterol in your food (dietary cholesterol) doesn't have much effect on your blood levels. So eggs, shellfish and liver which are high in cholesterol can be eaten safely. What is much more important is the total amount of saturated fat in your diet which has a significant impact on your blood cholesterol levels.

  • If you are overweight or obese. It's much more likely for you to have low levels of HDL (the good cholesterol) and much higher levels of LDL (bad cholesterol). Levels of other blood fats such as triglycerides are also likely to be increased.

  • If you are sedentary. If you don't do much exercise or physical activity this can also increase the levels of bad cholesterol in your blood and increase your risk.

  • If you smoke. Chemicals in cigarette smoke further increase the risk of narrowing of the arteries (atherosclerosis) which prevents HDL (good cholesterol) carrying the cholesterol away from your arteries to the liver.

  • If you drink excessive alcohol. Finally if you drink excessive amounts of alcohol this also increases your cholesterol and triglyceride levels which can contribute to an increased risk in heart disease.

 

High Cholesterol and Other Conditions

Your blood cholesterol levels can also be increased if you suffer from other health conditions including diabetes, kidney and liver disease or a thyroid disorder. So it's important that you manage existing conditions appropriately so as not to increase your risks here.

 

‘Fixed Factors' That Affect Your Cholesterol Levels

As well as lifestyle factors and other health problems it's possible you also experience an increased risk from heart attack or stroke due to a number of other factors that are outside of your control.

These include:

  • Your age. The older you are the more likely you are to develop narrowing of your arteries.

  • Your gender. Men are of a higher risk than women.

  • Your ethnicity. Particularly people of Middle Eastern descent have an increased risk from heart disease

  • Family History. You're also more likely to have high cholesterol if there's a family history of coronary heart disease or stroke especially if they're an immediate male relative under the age of 55 or a mother or sister aged under 65.

Obviously you can't do anything about your fixed factors directly, so it makes focusing on the lifestyle risks that you can influence even more important if you are at risk.


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Cholesterol: The Good & The Bad: References & Citations

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