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Fatty acids when present in food may be either
saturated or unsaturated.
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Saturated fatty acids
If the fatty acid has all the hydrogen atoms it can hold it is said to be saturated
(see below)
This type of fat is typically found in larger amounts in foods from animals,
e.g. meat, butter, cheese and cream. Many baked goods such as cakes, biscuits and pastries are also high in saturated fat. Excessive intake of saturated fat can increase blood cholesterol levels, one of the major risk factors for heart disease.
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Unsaturated
Some of the carbon atoms are joined to others by a double bond and so are not completely saturated with hydrogen atoms (see below). They could therefore accept more hydrogen atoms:
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There are three types of unsaturated fatty acids:-
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Monounsaturated fatty acids
If there is one double bond as above, the fatty acid is known as a monounsaturated fatty acid. This is found in significant amounts in most types of nuts, avocado pears, rapeseed oil and olive oil. Monounsaturates do not raise blood cholesterol and evidence shows that they may also help to reduce blood cholesterol levels if they replace saturated fat in the diet.
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Polyunsaturated fatty acids
If there is more than one double bond, then the fatty acid is known as a polyunsaturated fatty acid (see below). These come mostly from vegetable sources, such as sunflower oil or seeds, but are also found in oily fish such as mackerel and sardines.
Polyunsaturates can actively reduce blood cholesterol levels and are found largely in sunflower and corn oils. Polyunsaturates in oily fish appear to have no effect on blood cholesterol levels, but they do make blood less 'sticky' and therefore less likely to form clots that can block the flow of blood to the heart and cause problems.
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Trans fatty acids
Trans fatty acids in our diet come mainly from two sources. One is when liquid oils are hardened by partial
hydrogenation; the other source of trans fatty acids are meat products and dairy foods. Current scientific evidence suggests that trans fats behave in a similar way to saturated fats,
i.e. raising blood cholesterol levels.
For an example of the trans fatty acids configuration see below:-
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[ Up ] [ What is a Fat/Oil Chemically ] [ The Difference between Fat and Oil ] [ What does Fat provide in the Diet ] [ What are the Different Types of Fatty Acids ] [ Typical Composition of Vegetable Oils ]
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