If proteins have been dubbed ‘Beauty’ by advertisers, fats are surely ‘The Beast’, for few nutrients have been subjected to as much suspicion by the health profession. This suspicion is sometime justified, although often for wrong reasons.
The confusion is understandable since the chemistry and metabolism of fats is more c0mplex than that of proteins and carbohydrates, that is, up to the point that need interest us.
There are two obvious characteristics of fats about which we are all aware. First, they are not soluble in water, hence the need for detergents to clean up after a fatty mixed grill.
Secondly, some fats are solid at room temperature, say butter, lard or margarine, while others are liquid, mainly the oils – olive, corn, peanut, etc.
These are good starting points for the study of the nutrition of fats, in that we must explain how fats, insoluble in water are digested and metabolized in the largely watery environment of the body and how the chemistry of fats can explain their physical properties.
The basic units of fats are known as fatty acids, but fat molecules are not made up of repeating fatty acid units. Fat molecules are known as triglycerides and are comprised of glycerol with fatty acids attached to the top, middle and bottom of the glycerol molecule. Hence fatty acids come in threes.
Like –proteins, there are no rules as to what fatty acids must occupy what positions on the glycerol molecule, or what mixes of three fatty acids should cling to a molecules of glycerol.
Three grouping of fatty acids:
- Saturated fats
- Monounsaturated
- Polyunsaturated fats
If you purchase a sample of pure saturated fatty acids from a chemical supplier you would find that they were solid at room temperature. Monounsaturated and polyunsaturated fatty acids would be liquid. Therefore the hardness or softness of a dietary fat depends on temperature and the balance between the three categories of fatty acid.
Fats
