Describing the importance of different kinds of fats in the human body. Explaining terms like Saturated, Mono-unsaturated and Poly-unsaturated, cis and trans.
The modern obsession with fats and cholesterol is due to a greater understanding of the role of the group of bio chemicals called Lipids. There are two important types of lipids that we hear a lot about. Cholesterol will be dealt with in another article.
Triglyceride Fats and Oils
First are the fats and oils. These are all triglyceride molecules based on glycerol, an organic molecule made up of a chain of three carbon atoms with a hydroxyl (OH) groups. Each hydroxyl group in glycerol connects to a long chain molecule called a fatty acid, resulting in a three-tailed molecule which is a triglyceride.
Fatty Acids
Fatty acids are important components of soap. This is because the carboxylic acid group at one end is soluble in water or hydrophilic. The rest of the molecule does not dissolve in water, it is hydrophobic, but it is attracted by oil and grease. So when added to water, fatty acids are able to attach their tails to the greasy dirt on your hands and, with only their hydrophilic heads showing, make the grease soluble in water.
Stored Fats
When they are reacted with glycerol to form triglycerides, the resultant fat molecules are totally hydrophobic. The human body stores fats because they are good stores of energy, storing twice as much energy as carbohydrates of the same weight. There are some fats, for example “Omega 3”, found in fish oil, which the body needs but cannot produce itself and so they must be consumed regularly.
Saturated Fats
There is a lot of talk about saturated and unsaturated fats and oils these days. What are they and what is the difference? The terms refer to the bonding between the carbons and hydrogens in the long chain of the fatty acids. In fats which come from animals, the chains are all bonded with single bonds, all the carbon atoms having all the hydrogen atoms attached possible. These are called saturated fats and, with the chains all lining up nicely, they are usually solid at room temperature.
Unsaturated Oils
When one of the carbon bonds in the chain is a double bond, there are two less hydrogens than there would be in a saturated fat, so it is called a mono-unsaturated fat. When there is more than one double bond it is called a poly-unsaturated fat. Double bonds make the carbon chains have kinks, the molecules cannot get close together and they tend to be liquid at room temperature. Unsaturated fats are better than saturated because the body can break them down easier and so they are used more quickly in the body’s metabolism.
Cis and Trans
These prefixes are often seen on nutritional information on foodstuffs. They relate to the shape of the carbon-carbon double bond. If the hydrogens are bonded to the same side of the double bond then it is a cis-bond. If they are bonded to opposite sides then it is a trans-bond. Cis-bonds are easier for the body to break down than trans-bonds and they are also more common in natural vegetable oils. If the oil is heated, then cis-bonds become trans-bonds. So oil that has been continually heated, like in a deep-fat fryer has more trans-bonds than oil that has only been heated once. So foods cooked in deep fat fryers contain more trans-bonds than those cooked in a frying pan.
