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LDL Cholesterol vs HDL Cholesterol; Complete Overview of Cholesterol

Updated on March 21, 2020
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I am Shrawan Kumar Upadhyay, a Biochemistry graduate with an aim to work in a Research Laboratory of Biochemistry.



What is Cholesterol?

Cholesterol is a saturated, pentacyclic hydrocarbon. It is also called as sterol or steroid alcohol. It is highly hydrophobic in nature, because of the presence of a saturated steroid nucleus (four rings fused together to form the steroid nucleus). Chemically, it is called as perhydro-cyclopentano-phenanthrene.

Cholesterol belongs to the non-saponifiable lipids and represents the third class of membrane lipids. Cholesterol comprises about 25% of total membrane lipids whereas rests are phospholipids and glycolipids. Cholesterol, along with other membrane lipids maintain the fluidity of the membrane.

Cholesterol is also important in the biosynthesis of steroid hormones (sex hormones), where it acts as a precursor molecule. It is a precursor molecule too that is used for the biosynthesis of Vitamin D and bile acids. So, if you say cholesterol is a bad thing, then you understand cholesterol in a misleading way. Cholesterol is not a bad thing but is an essential component. However, the level of its concentration determines its goodness or badness.

High Cholesterol vs. Low cholesterol

Cholesterol is an equally important biomolecule as others, but it is beneficial only to a certain level of its concentration. So, what determines the suitability and beneficial effects of the cholesterol? It is its appropriate level in the body. If the cholesterol level goes up beyond the standard level, then it is considered as a signal of high cholesterol that is associated with health problems.

Otherwise, it is normal and performs a necessary role in the body. The cholesterol level inside us is greatly influenced by the intake of foods. If we eat foods rich in cholesterol and fats, then we are adding extra cholesterol to our bodies.

Blood Cholesterol Levels

Blood Cholesterol Level Chart
High Risk
Total Cholesterol
Low Density Lipoprotein
High Density Lipoprotein

Cholesterol Levels

From the chart above, it is clear that what is the desired level of cholesterol and what concentration of cholesterol is the signal of high risk? When the cholesterol level goes up from the desired value, you have to think seriously to bring it down to the normal range. Cholesterol levels can be checked through blood testing. Many hospitals and clinics provide blood testing and cholesterol profiling.

As cholesterol is highly hydrophobic in nature, an excess of cholesterol starts forming a plaque-like structure, which gets deposited in the blood vessels and exerts pressure on the blood flow. The ultimate result is high blood pressure and blockage of the blood flow. If blood vessel blockage continues due to cholesterol deposition occurs in the blood vessels of the heart, then it may lead to a heart attack.

Composition of Lipoproteins

(click column header to sort results)
Density g/ml  
protein %  
Phospholipid %  
Free Cholesterol %  
Cholesteryl Ester %  
TAG %  

Egg Yolk Rich in Cholesterol


LDL Cholesterol vs. HDL Cholesterol

Actually, there is no such thing as LDL cholesterol or HDL cholesterol. LDL and HDL are the lipoproteins involved in cholesterol transport. There are four types of lipoproteins which are chylomicrons, VLDL, LDL, and HDL. All these are involved in lipid transport and are made of proteins and lipids (as the name suggests).

All these lipoproteins contain cholesterol, cholesterol esters, triglycerides, and free fatty acids. It is the amount that differs from one lipoprotein to another. As, for example, chylomicrons and VLDS are mainly involved in TAG (triglyceride) transport, while LDL and HDL are involved in cholesterol transport. Chylomicrons mainly transport TAGs from extrahepatic tissues to the liver, while VLDL transports TAGs synthesized in the liver to extra-hepatic tissues. LDL transports cholesterol synthesized in the liver to the extra-hepatic tissues while HDL transports cholesterol from extrahepatic tissues to the liver for metabolism. So which one is

Chylomicrons mainly transport TAGs from extrahepatic tissues to the liver, while VLDL transports TAGs synthesized in the liver to extra-hepatic tissues. LDL transports cholesterol synthesized in the liver to the extra-hepatic tissues while HDL transports cholesterol from extrahepatic tissues to the liver for metabolism. So which one is good cholesterol and which one is bad cholesterol?

It is not wise to say LDL as bad cholesterol and HDL as good cholesterol because they are doing their jobs for that they are assigned to. It's the concentration of these lipoproteins that appear to be the reason behind goodness and badness. If LDL is at the acceptable level, then there is no problem with LDL. If its concentration rises up than the acceptable (standard) value, then it becomes bad. Therefore, it can be wise to call as LDL cholesterol or HDL cholesterol, instead of saying good cholesterol or bad cholesterol.

In a recent study, it has been shown that HDL cholesterol can also be bad sometimes. This is because there may be a problem with the HDL cholesterol transporter.

Foods that lower cholesterol


Synthesis of Cholesterol

Cholesterol is synthesized in our body within the liver (hepatocytes). Acetyl CoA (coming from the β-oxidation of fatty acids) is the starting material for the cholesterol biosynthesis. If you are taking an excess of fats and fatty foods than required, you are accumulating fats in your body and it is one of the big reasons behind the high cholesterol levels.

As a fat, upon digestion releases free fatty acids, which upon further oxidation in the mitochondria release acetyl-CoA. Excess of acetyl-CoA is either utilized to synthesize fatty acids and thus fats to be stored in adipocytes or utilized to synthesize cholesterol. Both of which, if formed in excess than what is required, becomes bad and increase the risk of different health problems.

So you need to take care of your own health and need to know which food is good for health and which food is bad for health.

Cholesterol Content of some foods

(click column header to sort results)
Food products  
Cholesterol (mg/100g)  
Egg yolk
Fish oil
Pork liver
Crab meat
Cream cheese
Evaporated milk

Foods That Lower Cholesterol and High Cholesterol Diets

Foods prepared from oatmeal, barley, and wheat are rich in soluble fibers and slow down the intestinal absorption of the cholesterol. Eating fish, like salmon may lower your cholesterol levels that is because they contain ω-3 fatty acids, which are involved in the biosynthesis of eicosanoids involved in pain and inflammation management.

Some eicosanoids are also involved in cleaning blood clots and plaques deposited inside the blood vessels. Walnuts, almonds contain proteins and minerals along with plant sterols, which lower the blood cholesterol. Potato is also one of the cholesterol-lowering food.similarly soy products and soy milk are rich in protein and saturated fatty acids and helps lower cholesterol levels.

Eggs, liver, kidney, seafood like prawn, milk products, meats, cheese are all rich in cholesterol and should be avoided to lower the cholesterol level. Above is the table of the cholesterol content of some food products.

© 2015 Shrawan Kumar Upadhyay


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