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The second issue with regard to selecting which vegetable oil to use in cooking revolves around the health benefits derived from the fatty acid composition.

Olive oil has 70-80% oleic acid which is a monounsaturated fat, and 8-10% polyunsaturated fats. On the other hand most other vegetable oils contain less monounsaturated fats and more polyunsaturated fats. Fats derived from animals have a high level of saturated fats.

The main saturated fats in olive oil are myristic, palmitic and stearic, The main. monounsaturated fat is oleic and polyunsaturated fats are linoleic and linolenic.

The ratio of the different degrees of saturation are important from both a health and cooking perspective.



A comparison of the fat content of various other vegetable, oils is given in the table below (main source Wikipedia) showing that canola oil and avocado oil compare favourably with olive oil in high oleic acid (monounsaturated fat) content.

 

Fat

Saturated

Monounsaturated

Polyunsaturated

Animal Fats

%

%

%

Lard

40.8

43.8

9.6

Duck Fat

33.2

49.3

12.9

Butter

54.0

19.8

2.6

 

 

 

 

Vegetable oils

 

 

 

Coconut oil

85.2

6.6

1.7

Palm oil

45.3

41.6

8.3

Cottonseed oil

25.5

21.3

48.1

Wheat Germ oil

18.8

15.9

60.7

Soya oil

14.5

3.2

56.5

Olive oil

14.0

69.7

11.2

Corn oil

12.7

24.7

57.8

Grapeseed oil

11.0

16.0

72.0

Sunflower oil

11.9

20.2

63.0

Safflower oil

10.2

12.6

72.1

Hemp oil

10.0

15.0

75.0

Canola/Rapeseed Oil

5.3

64.3

24.8

Rice Bran oil

20.0

47.0

33.0

Avocado oil

20.0

65.4

15.5

Walnut oil

15.0

1.0

84.0

Comparison fatty acid percentages in animal fats and vegetable oils

There is an important difference in how saturated, polyunsaturated and monounsaturated fatty acids behave in relation to cholesterol movement through the body. Cholesterol is important in the structure of cell membranes.

Fats and cholesterol are not water soluble so when we ingest them they are transported as lipoprotein complexes in the blood. Large lipoproteins (high density lipoproteins -HDLs) are formed in the intestine and carry the triglycerides (fats) and cholesterol we eat to the liver. From the liver, after some processing, low density lipoproteins (LDLs) carry the lipids in the blood to the adipose (fat storage tissue). The LDLs are the main cholesterol carriers to the cells. There is a complex system that results in the cholesterol being dropped off at the cells for use in building and maintaining cell membranes, manufacturing bile acids, steroid hormones and fat soluble vitamins. But if anything goes wrong with the system, the LDLs cannot deliver the cholesterol at the right spot and it gets dumped in the arteries and causes the blockage problems we hear so much about.

Now, saturated fatty acids inhibit LDL receptors in the cells. Polyunsaturated fatty acids also inhibit cell cholesterol uptake. But, monounsaturated fatty acids do not inhibit cholesterol uptake by the cells and raises HDL levels. So olive oil, high in monounsaturated fats helps the body deal with excessive amounts of cholesterol.

Monounsaturated fats also seem to play a protective role in preventing cell mutation causing cancer. The genetic code of each cell normally contains oncogenes which can stimulate cell proliferation. These genes are usually repressed and not active. They are sometimes activated to repair damage but in tumours they are permanently active causing uncontrolled cell proliferation. The ‘switching on’ of these genes can be done by tumour inducers causing a mutation, inducers can be chemical, physical or biological. When activated, tumour promoters help perpetuate the proliferation. Promoters can be hormones, chemicals or dietary substances.

Monounsaturated fatty acids, as found in olive oil, appear to exert a protective effect against this process. This is evidenced by the relatively low incidence of tumours in Mediterranean countries where large amounts of olive oil are consumed. However, other components of the diet and lifestyle are sure to contribute to this low incidence.

In addition to the monounsaturated fats, anti-oxidants in extra virgin olive oil also appear to play an important role as anti-promoters of carcinogenesis.

The anti-oxidants, despite making up a small percentage of vegetable oils are polyphenols and other compounds found in unrefined oils. Most vegetable oils, unlike extra virgin olive oils, undergo some degree of refining when the bleaching and deodorising process destroy the anti-oxidants.

So in summary, extra virgin olive oil with its high monounsaturated fat level and anti-oxidants compares very favourably with other vegetable oils on the supermarket shelf.