Hi, this is Shrawan Kumar Upadhyay, a biochemistry graduate aimed to work in a biochemical research laboratory. Hoping my dream comes true.
What is cholesterol?
Let's first know what cholesterol really is. Cholesterol is a saturated, pentacyclic hydrocarbon. It is also called sterol or steroid alcohol that is because it contains a hydroxy group (-OH). It is highly hydrophobic due to the presence of a saturated steroid nucleus (four rings fused to form a steroid nucleus). Chemically it is called perhydro-cyclopentano-phenanthrene.
Cholesterol belongs to the non-saponifiable lipids and represents the third class of membrane lipids. It comprises about 25% of total membrane lipids whereas the rests are phospholipids and glycolipids. Cholesterol, along with other membrane lipids, maintains the membrane fluidity of the cell.
Some essential functions of cholesterol
Besides maintaining membrane fluidity, cholesterol is also essential in the biosynthesis of some of the biomolecules such as steroid hormones (sex hormones), vitamin D, and bile acids. Cholesterol acts as a precursor molecule in these biosynthetic mechanisms.
So, if you say that cholesterol is a bad thing or not good for our health then you must be misled by someone or have misunderstood cholesterol. Cholesterol is not a bad thing by itself but is an essential component. However, it is the level of cholesterol in our body that determines its goodness or badness.
Anything that is in excess amount in our body is not good anyway. So, let's just understand the goodness and badness of cholesterol in a detailed way.
High cholesterol vs. low cholesterol
Cholesterol is an equally important biomolecule as others, but it is beneficial only to a certain level. So, what determines the suitability and beneficial effects of cholesterol? It is its appropriate level in the body. If the cholesterol level goes up beyond the recommended level, then it is considered a signal of high cholesterol that is associated with various health problems.
Otherwise, it is normal and performs many necessary roles in our body. The cholesterol level inside our body 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. That's simple.
Blood cholesterol levels
|Blood Cholesterol Level Chart||Desirable||Borderline||High Risk|
Low Density Lipoprotein
High Density Lipoprotein
From the chart above, it is clear what the desired level of cholesterol is 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. There are various ways of estimating blood cholesterol. you may want to read this salkowski's method of estimating blood cholesterol levels.
As cholesterol is highly hydrophobic, an excess of cholesterol starts forming a plaque-like structure, that 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 occurring in the blood vessels of the heart, then it may lead to a heart attack.
Composition of lipoproteins
|Lipoprotein||Density g/ml||protein %||Phospholipid %||Free Cholesterol %||Cholesteryl Ester %||TAG %|
Egg yolk rich in cholesterol
LDL cholesterol vs. HDL cholesterol
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 and these are chylomicrons, VLDL, LDL, and HDL. All of these are involved in lipid transport and are made of proteins and lipids (as the name suggests).
All these lipoproteins contain cholesterol, cholesteryl esters, triglycerides, and free fatty acids. It is the amount of cholesterol that differs from one lipoprotein to another.
For example, chylomicrons and VLDLS 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 good cholesterol and which one is bad cholesterol?
It is not wise to say LDL is bad cholesterol and HDL is good cholesterol because they are just doing their jobs for what 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 an acceptable level, then there is no problem with LDL. If its concentration rises than the acceptable (standard) value, then it becomes bad. Therefore, it can be wise to call as LDL or HDL, instead of saying good cholesterol or bad cholesterol. So, be clear about it.
Foods that lower cholesterol
Synthesis of cholesterol
Cholesterol is synthesized in our body within the liver cells called hepatocytes. the starting material of cholesterol synthesis is Acetyl CoA which comes from the β-oxidation of fatty acids. If you are taking an excess of fats or fatty foods than what is required, then you are accumulating fats in your body. That is one of the big reasons behind high cholesterol levels.
After digestion, fats get converted to fatty acids that are absorbed by the small intestine. During normal metabolism, these fatty acids are further broken down to acetyl-CoA in the mitochondria through the process of β-oxidation.
Excess of acetyl-CoA is either utilized to synthesize fatty acids and be stored in adipocytes or utilized to synthesize cholesterol. If produced in excess amount than required, both of these cases become bad and increase the risk of various health problems.
That's why you need to take care of your health and need to know which food is good and which one is bad for your health.
Cholesterol content of some foods
|Food products||Cholesterol (mg/100g)|
Foods that lower cholesterol
Foods prepared from oatmeal, barley, and wheat are rich in soluble fibers. These are the foods that slow down the intestinal absorption of cholesterol. Eating fish (e.g. salmon) may also lower your cholesterol levels that is because they contain ω-3 fatty acids. These ω-3 fatty acids are involved in the biosynthesis of eicosanoids responsible for pain and inflammation management. Some of the eicosanoids are also involved in cleaning blood clots and plaques deposited inside the blood vessels.
Walnuts and almonds contain proteins and minerals along with plant sterols, that lower 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 help lower cholesterol levels.
Diets that are rich in cholesterol
Eggs, liver, kidneys, seafood like prawns, milk products, meats, and cheese are the foods that are all rich in cholesterol and therefore these foods should be avoided to lower the cholesterol level. I have prepared a table shown above to inform you cholesterol content of various food products.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2015 Shrawan Kumar Upadhyay