Why the fuss about fats?
Fat is a nutrient with important functions:
- It is a rich source of energy, providing more than double that of either carbohydrate or protein.
- It is a carrier for the fat-soluble vitamins – A, D, E and K.
- It provides the essential fatty acids, linoleic and alpha-linolenic acid, which are polyunsaturated.
Not all Fats are the Same
To remain healthy, we need moderate amounts of the right type of fats eaten as part of a good, balanced diet. However, a high fat intake – and in particular, a high intake of saturated fats – is associated with raised blood cholesterol and coronary heart disease.
Fats are made up of fatty acids and glycerol. A fatty acid consists of a chain of carbon atoms, where each carbon atom in the chain is attached to hydrogen atoms. The number of hydrogen atoms per carbon atom determines whether the fatty acid is saturated or unsaturated.
If a fatty acid has all of the hydrogen atoms it can hold (2 per carbon atom in the chain) and all of the carbon atoms in the chain are linked by single bonds, it is described as saturated. Saturated fats are usually solid or semi-solid at room temperature, and are strongly associated with raised blood cholesterol – which is why nutritionists recommend eating them as little as possible.
Lard, butter, hard cheeses, whole milk, animal fats and palm and coconut oils – plus products containing them – all contain high levels of saturated fat.
If a pair of carbon atoms in the fatty acid chain is linked by a double bond instead of a single bond, the fatty acid is described as monounsaturated. Fats rich in monounsaturates tend to be liquid at room temperature. Olive Oil is one of the richest sources of monounsaturated fatty acids.
These contain more than one double bond and are liquid at room temperature. The main sources are vegetable oils, such as sunflower oil, corn oil and rapeseed, but not tropical oils such as coconut, palm and palm kernel oils.
Trans fats are created when a hydrogenation process is applied to solidify oil for use in margarines or to improve a product’s shelf life. This processing causes trans fats to act like saturated fats.