Dietary Hazards-Processed Fats

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Dietary Hazards-Processed Fats

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In today's world the appearance, texture and colour of food is often

considered of greater importance than the nutrient value of such

food. In an instant world we need instant food, and to avoid

spoilage and financial loss, such food is often chemically

manipulated to obtain all these desired effects.

When the chemical nature of our food is changed so that it meets the

requirements of the marketplace, then the risk is great that it no

longer meets the requirements of the body.

Our bodies are designed to interact with the environment in a highly

specialized way, and any interference with this delicate balance may

impact negatively on the system.

 

Modern Oil Refining Techniques

 

Extracted oil undergoes a series of steps which adversely affects

its nutritional value. Free fatty acids are removed by vacuum

extraction and precipitation. Furthermore, the oil is filtered and

heated to 220 °C to obtain a clear liquid.

In order to obtain a less fluid oil, suitable for the production of

margarine, the oil is further subjected to the process of

hydrogenation, to which liquid oils nowadays are also partially

subjected.

 

This process was developed by W. Norman in the year 1900 and

involves a catalytic reaction which changes cis fatty acids to trans

fatty acids, thus rendering them less fluid by changing the shape of

the molecules.

 

Polyunsaturated fats contain double bonds, and this gives rise to

the possibility of cis-trans conversions. In nature, fatty acids

occur mainly in the cis configuration, which means that the carbon

chains on either side of the double bond are spatially arranged on

the same side of the double bond. (See table)

 

Trans fats do not form part of the normal diet and should not be

introduced into the system as they can result in a number of

biochemical changes, and together with saturated fats and

cholesterol, can lead to altered membrane structure and concomitant

hardening of the arteries.

The essential fatty acids (linoleic and linolenic acids) also

naturally have the cis configuration but the free use of extracted,

partially hydrogenated oil, rich in linoleic acid (found in corn,

safflower and sunflower oils), has been associated with cancer

promotion.

Linoleic acid is the substrate from which prostaglandins are

manufactured, and trans-linoleic acid can result in altered

prostaglandins, thus modifying the effect of these hormones or even

producing opposite effects.

Because leucotrienes play an essential role in regulating the immune

system in that they are involved in the production of antibodies and

the destruction of viruses and cancer cells, it is essential that

these molecules be produced from essential fatty acids that have the

correct configuration so that the delicate balance and the function

may not be jeopardized.

 

The molecular changes found in even partially hydrogenated oils can

adversely affect the relationship between the various prostaglandins

as well as changing them structurally.

 

Trans fatty acids depress serum levels of prostaglandins. Moreover,

hydrogenated oils do not share the properties of normal unsaturated

fats and will also not lower cholesterol levels as do the natural

oils in whole foods.,[ii]

The consumption of trans fatty acids in the Western world is quite

high, and it has been estimated that in the US and in Canada, men of

20-39 years of age consume 11-12 g per person per day of these

fats.2 The British Medical Committee on Cardiovascular Diseases

proposed new guidelines in 1994 on recommended consumption of fatty

acids.

Recognizing that trans fatty acids have an undesirable effect on HDL

and LDL cholesterol and coronary disease mortality, they suggested

that no more than 2% of caloric intake come from this source, and

that the amount should even be reduced.[iii]

Margarine

Margarine is typically manufactured from the oil of soya beans,

maize, sunflower seeds, olives, coconut and palm, with the addition

of substances which enhance the flavour and act as preservatives and

texturisers.

The typical ingredients of margarine include a combination of oils,

water, sodium chloride, vitamins A, D and E, lecithin or other

emulsifier, preservatives such as sodium benzoate and/or potassium

sorbate, milk solids including casein, colorants such as beta-

carotene and retinyl esters, flavourants such as butter distillate

or simulated butter taste chemicals.

The manufacturing process of margarine involves a combination of a

number of steps. The fat-insoluble gums and other substances from

the crude oil are first removed and then the oil is neutralized with

alkali.

Subsequently it is bleached, filtered, deodorized and in most cases

hydrogenated. After this the product is again subjected to further

filtration, neutralixation, bleaching, deodorization and blending.

Finally, colorants, flavourants, vitamins, emulsifiers and

preservatives are added, and proportioning (creating the desired

balance between water and fat), emulsification, chilling and

packaging round off the final product.

In most cases, margarines exceed the recommended maximum levels for

saturated and trans-unsaturated fatty acids, but some countries

(Germany) have taken cognizance of the detrimental effects of trans

fatty acids and many of the margarines, shortenings and cooking fats

in Germany are being produced essentially free from trans fatty

acids.

Nevertheless, a concentrated, chemically manipulated, unnatural food

such as margarine must place excessive demands on the system, and

viable alternatives should be sought.

Artificial foods are however the vogue, and large quantities of

spreads and non-dairy creamers are consumed annually.

Non-dairy creamers also contain extracted saturated and hydrogenated

plant oils of coconut and palm origin, and therefore contain no less

fat than dairy cream.

There are many ways to prepare palatable meals without the use of

extracted oils, and their use can thus be limited. The best way of

obtaining chemically sound fats, suitable for maintaining the fine

chemical balances of the body, is to eat whole food that has not

been changed by modern refining techniques.

Whole grains, seeds, nuts as well as oil-rich fruits such as avocado

pears and olives, together with other plant sources will supply an

abundance of fats of the variety required by the body.

The Use of Oil in the Frying of Food

The frying of food in oil or lard also has detrimental effects.

Studies have shown that heated oils and fats undergo autoxidation

and that the rate of autoxidation is proportional to the degree of

unsaturation and the presence of absence of pro- and anti-oxidants.

It has been established that animal fats undergo autoxidation more

readily than oils of plant origin,

in spite of the fact that animal fats are saturated fats, but this

has been attributed to the virtual absence of natural antioxidants

in animal fats.

Polyunsaturates, however, sustain the most thermo-oxidative damage

when oil is heated.

In this regard it is enlightening that a tri-unsaturated fatty acid

will undergo autoxidation 10 000 times more readily than a

monounsaturated fatty acid.[iv]

The rate and degree of autoxidation of unsaturated and saturated

fats is presented in figure 3.10.

Source: Grundy, S.M. 1989. Monounsaturated fatty acids adn

cholesterol metabolism: Implications for dietary recommendations. J.

Nutr. 119:529

Heat Damage Sustained By Oil

The products formed in fats and oils that are heated to high

temperatures are peroxides, aldehydes, ketones, hydroperoxides,

polymers and cyclic monomers, any one of which can have toxic

effects.

Subjecting saturated and polyunsaturated fats, such as butter and

sunflower oil to temperatures of 170 °C for two hours will also

alter the composition that if fed to experimental animals they will

induce liver ailments in these animals.

If animal fat, polyunsaturated oil, and even monounsaturated oil

such as olive oil, is however heated to 180 °C for longer periods of

time, serious liver disorders are induced in experimental animals

that are fed these oils.

[v] The peroxidised fatty acids in heated fats also affect the

cardiovascular system, possibly even causing lesions in the cardiac

muscles and arterial lining as well as enhancing clot formation.[vi]

As most processed oils are heated to 220 °C during the manufacturing

process, and are still further heated during the frying process, the

use of free oil should for these reasons alone, not be encouraged.

The frying of food should therefore be avoided if healthful living

practices are introduced into the household.

This does not necessarily mean that taste should be sacrificed, but

it does mean that age-old habits will have to be revised and

substituted with a little bit of ingenuity.

If oil is used at all, it should be used in moderation and the cold-

pressed variety should be used as this have been least subjected to

heat during the extraction and clarifying processes.

Also oils rich in monounsaturated fats, such as olive oil, should be

the oils of choice as monounsaturated fats undergo the least damage

during heating.

Whilst it is true that increased dietary consumption of

polyunsaturated fats has led to a decrease in cholesterolaemia and

associated drop in cardiovascular disease, it has been accompanied

by a rise in deaths from non-vascular diseases such as cancer,[vii]

cholelithiasis[viii] and a general drop in life expectancy,[ix]

probably resulting from the peroxidation of the polyunsaturates.

Peroxidation of polyunsaturates takes place because these molecules

are unstable, and the more double bonds there are in the molecules

the more readily the process of peroxidation takes place.

During this process " free radicals " are formed which are extremely

reactive in view of their unpaired electron.

Free radical formation is largely prevented in whole foods, as

natural antixodants, which are present in these foods, prevent their

formation. A natural balance exists between antioxidants such as the

fat-soluble vitamins A and E and the quantity of polyunsaturated

fats that are present in whole foods.

An imbalance between polyunsaturates and antioxidants will result in

a rise in free radical formation with concomitant harmful results

such as an increase in the rate of the aging process,[x]

inflammation,[xi] carcinogenesis,[xii] liver disorders and

arteriosclerosis.[xiii]

Unfortunately modern food processing techniques often strip food of

the essential fatty acids and vital prepacked antioxidants and in

this way deprive the system of these essential nutrients.

During the refining process grains, for example, are stripped of the

germ, which contains the essential oils and fat-soluble antioxidant

vitamins in a perfect biorelationship, and the lack is then

substituted for with large intakes of disproportionate combinations

of processed oils and fats.

In this regard it is enlightening to note that the daily vitamin E

requirements (which amount to about 10 mg per day) increases 20 fold

it polyunsaturates are added to the diet.[xiv]

It is doubtful whether any diet will supply this additional

requirement without supplementation, and it is therefore not

surprising that the degenerate diseases are so prevalent in Western

societies.

The eating of whole foods that have not been stripped of their

essential components will supply all the essential oils required in

healthful combinations and should therefore be encouraged.

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Reference:

Jonnalagagadda, S.S., Mustad, V.A., Yu, S., Etherton, T.D., Kris-

Etherton, P.M. 1996. Effects of individual fatty acids on chronic

diseases. Nutrition Today. 31 (3) May/June 1996.

[ii] Mensink, R.P., Katan, M.B. 1990. Effect of dietary trans fatty

acids on high-density and low-density lipoprotein cholesterol levels

in healthy subjects. New Enlg.J.Med. 323:439.

[iii] Nutrition Today Newsbreaks. 1995. British scientists endorse

new fatty acid guidelines. Nutrition Today. 30 (1), January/February

1995. P.5.

[iv] Fedeli, E. 1984. La auto-ossidazione Lipidica. In: Simp. Su

Rrilettura di un problema: 1 lipidi Alimentari:, Rimini (Italia)

[v] Alexander, J.C. 1978. Biological effects due to changes in fats

during heating. (In: Symp. On frying oils, Presented at AOCS 68th

Annual meeting, New York City, New York (USA) 11.5 1977). J.Am.oil

Chem.Soc. 55:711.

[vi] Giani, E., Masi, I., Galli, I. 1985. Heated fat, vitamin E and

vascualr eicosanoids. Lipids. 20:439.

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