Fats and oils are made of building blocks known as fatty acids. But all fatty acids are not created equal. Some are toxic, others are essential for health. An essential fatty acid is one which cannot be synthesized by the body from others, but must be obtained through your diet.

Essential fatty acids are needed for the proper functioning of many body parts and systems, for example:

• They are part of every cell membrane.

• They comprise part of the myelin sheath which coats the nervous system.

• They are essential for the immune system.

• They are needed for soft healthy skin and hair.

• They play a role in the healthy functioning of the reproductive system.

• They make prostaglandins: compounds which balance inflammatory reactions in the body.

But it is very easy to have a high fat diet and still be deficient in essential fatty acids.

Fatty acids are easily destroyed by heat, light and oxygen. This means that when food is cooked, its fatty acid molecules are destroyed, leaving them unusable and unrecognizable as food by your body.

These damaged molecules are termed 'free radicals'. They are highly reactive, and bind easily to other things in your body, forming many toxic by-products. Some of these are highly carcinogenic.

As well as free radicals, oils heated to high temperatures, such as those used for deep-frying, acquire another dangerous component: trans fats. Among a myriad of other disturbances in normal body physiology, trans fats are known to increase the risk of heart disease and cancer.

However when you eat foods which are raw then you ingest the essential fatty acids intact. High fat foods such as avocados and nuts do not have at all the same detrimental effect on your physiology when they are raw.

In terms of trans fats and free radicals, deep-fried fish and chips are among the most toxic things you can possibly eat. When oils have been repeatedly heated to high temperatures the proportion of trans fats and free radicals becomes extremely high.

Eating deep-fried foods, which are cooked at extremely high temperatures, means that not only do we become deficient in the fatty acids we need, we also have to cope with the huge amount of toxic waste products brought into our bodies by the heat-damaged fats and oils.

A fatty acid is saturated when there are no free spaces along its molecular chain structure for any more hydrogen atoms to attach (i.e. there are no double bonds). It is unsaturated when there are spaces available (meaning there are one or more double bonds). Saturated fats are solid, such as those in animal fats and coconut oil. Unsaturated fats are liquid oils.

A diet high in fat is known to be linked to atherosclerosis and coronary heart disease. It raises the blood lipid (fat) levels, making the blood thick and reducing its oxygen-carrying capacity. This means every cell in the body becomes slightly oxygen-starved, which translates into low vitality, poor health and reduced mental concentration.

A diet high in cooked unsaturated fats produces a large amount of free radicals (molecular by-products of the body's metabolism). Free radicals cause oxidation throughout the body (an example of oxidation is rust, which is the result of iron being oxidised) which is considered by some nutritionists to be a contributing factor in auto-immune and degenerative diseases such as cancer.

Butter is saturated fat in a close-to-natural state. It usually has very few additives, and these are often harmless or even beneficial things such as turmeric or carotene which are added for colour. (However the added salt can mask a degree of rancidity in the butter.)

Margarine is made from oils that were originally unsaturated, but have been partially saturated through the process of hydrogenation in which extra hydrogen atoms are forced onto the molecule at high temperatures. In the processing most of the vitamins and minerals are removed, along with the lecithin and some of the essential fatty acids. The margarine is then bleached and deodorised, after which a number of colourants, flavourings and preservatives are added to it.

Another thing that happens to vegetable oil in the process of becoming margarine is that the high heat changes some of its molecules from the 'cis' form to the 'trans' form. These trans fatty acids have different properties to their unsaturated origins. When the body attempts to use these fatty acids for the usual functions, it finds that they make cell membranes which are too porous and blood platelets which are too sticky. They also increase cholesterol levels and block essential fatty acid use.

When a label declares 'made from polyunsaturated vegetable oil' it is technically correct. Margarine is originally made from polyunsaturated oils, but by the time it becomes margarine, there is very little of these oils left in their original form.

The conclusion? Neither butter nor margarine are especially health-giving spreads to put on your hot toast in the mornings. If there is any slight advantage of one over the other, perhaps butter comes out looking slightly better, as it is less artificial.

You are probably familiar with how heavy and dull you feel after hot chips or a rich greasy meal. What is happening to your energy?
The state of the mind, reflects that of your digestive system to a large extent. When your stomach is full of heavy or oily food, your clarity of mind is also affected, being dampened into a state of inertia. It is interesting that even though fat theoretically provides you with an enormous amount of energy (in terms of calories), its immediate effect on you is exactly the opposite.

For those wishing to read further on the topic of fats, I recommend these excellent books:

On the lighter side...