A chemical description of an infamous but important chemical which is ever-present in dietary advice.
There are two main types of Lipids. The first type is triglyceride fats and oils. These are dealt with in another article. The second type is cholesterol. Of all dietary issues, our cholesterol level is probably top of the list for many people. But, what is cholesterol and why is it so bad for us?
Cholesterol is a molecule made up of three parts. First there is a hydroxyl group. This group is soluble in water. Next there is a steroid ring section. Finally there is a hydrocarbon chain. This is hydrophobic (it does not dissolve in water). It does, however, dissolve in fatty and oily substances.
The human body needs cholesterol. Animal bodies also need cholesterol. Both human and animal bodies produce cholesterol in order to make steroid hormones like testosterone and oestrogen. These hormones are based on the steroid ring section and the hydroxyl group in cholesterol. Hormones play and important role in the biochemistry of the body.
Other ways that the body uses cholesterol include:
The body needs a certain amount of cholesterol. Today’s diet and certain inherited genetic tendencies mean that there is often too much cholesterol in our blood stream. Scientific research has suggested that high cholesterol can cause a build up of hard matter on the walls of arteries which could result in a heart attack. Current medical advice is to limit the amount of foodstuffs which are high in cholesterol in our diet. It is important not to eliminate cholesterol from our diet, we do need some for the processes listed above, but we should be careful to control the amount.
Much dietary advice talks about “good cholesterol” and “bad cholesterol”. What is the chemistry of this distinction? The truth is that there is only one type of cholesterol. There is, however, a difference between the ways it is transported around the body. A type of chemical called lipoprotein is used by the body to transport cholesterol around the body. There are two main types of lipoproteins: Low Density Lipoprotein (LDL) and High Density Lipoprotein (HPL).
Lipoproteins have water-soluble protein sections and water-insoluble lipid sections. They make a ball around cholesterol with the protein sections on the outside so that the cholesterol can be transported by the blood. HDL takes cholesterol from the blood stream into the liver where it is recycled or eliminated from the body. LDL takes cholesterol to the places where it is needed. If there is too much LDL, then there will be too much cholesterol in the blood stream and more probability of thickening of artery walls and health problems.