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As well as other nutrients such as vitamin E, vegetable oils contain essential fatty acids,
needed for metabolic purposes. It provides energy. Vegetable oils are usually unsaturated,
and animal fats saturated. Unsaturated fats have lower melting points. Most vegetable oils
are liquid at room temperature and animal fats are solids.
Which is healthier?
Generally, it is thought that unsaturated fats are healthier than saturated fats. This is
because saturated fats increase the amount of cholesterol in the blood, which may block up
arteries, increasing the risk of heart disease.
Using fats in cooking
Fats have higher boiling points than water. So, cooking food by frying is a lot faster than
cooking food by boiling. Plus, frying produces new, interesting flavours and increases the
energy content of food.
Oils and fats contain long chain molecules with lots of carbon atoms. They can be saturated
or unsaturated. Unsaturated oils contain double bonds between some of the carbon atoms
in their carbon chains. They are called unsaturated fats because they could hold more
hydrogen atoms. Monounsaturated fats (in rapeseed and olive oils) contain one C=C double
bond in their carbon chains but polyunsaturated fats (in sunflower, corn oils and soya)
contain more than one C=C double bond. Polyunsaturated fats are supposed to be better for
your health. A saturated fat contains many C-C bonds but no C=C bonds.
Unsaturated vegetable are liquid at room temperature. By reacting them with hydrogen in
the presence of a nickel catalyst, at about 60 degrees Celsius, they can be hardened.
Hydrogenated oils have higher melting points than unsaturated oils so they're more solid at
room temperature. This makes them useful as spreads and for baking cakes. Margarine is
made from partially hydrogenated vegetable oil (if you turned all double bonds in vegetable
oil to single bonds it would make margarine too hard and difficult to spread.)Hydrogenating
most gives margarine its desirable buttery, spreadable consistency, and gives it a longer
shelf life. However, partially hydrogenating vegetable oils means you'll get trans fats. There is
evidence that trans fats are very bad for your health.
Why are they bad for your health?
Trans fats behave similarly to saturated fat-they raise level of Low Density Lipoproteins
(`bad' cholesterol) but they also decrease levels of High Density Lipoproteins (`good'
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Trans fats also increases the blood levels of two more artery cloggers -
triglycendes and lipoprotein(a). All of these elements work together to clog arteries, causing
an increased risk of coronary heart disease. There are also other health problems attributed
to eating trans fats, such as cancer and diabetes but these have not been scientifically
We still need some fat in our diet.…read more