Saturday, 16 August 2008

High Cholesterol : Fact or Fiction Pt 5

Cary G Dean.

Polyunsaturated fats and Cancer

Body cell walls are made of cholesterol.

The human body's fat make-up is largely of saturated and monounsaturated fatty acids.

We contain very little polyunsaturated fat.

Cell walls have to allow the various nutrients that body cells need from the blood, but stop harmful pathogens.

They must be stable.

An intake of large quantities of polyunsaturated fatty acids changes the constituency of cholesterol and body fat.

Cell walls become softer and more unstable.

Many laboratories have shown that diets high in polyunsaturates promote tumours.

It has been known since the early 1970s that it is linoleic acid that is the major culprit.

As Professor Raymond Kearney of Sydney University put it in 1987:

"Vegetable oils (eg Corn oil and sunflower oil) which are rich in linoleic acid are potent promoters of tumour growth."

Carcinogens - background radiation, ultraviolet radiation from the sun, particles in the air we breathe (Depleted Uranium) and the food we eat - continually attack us all.

Normally, the immune system deals with any small focus of cancer cells so formed and that is the end of it.

But linoleic acid suppresses the immune system.

Indeed it is so good at this that in the 1970s sunflower oil was given to kidney transplant patients to prevent kidneys being rejected - until an excess of cancer deaths was reported.

With a high intake of margarine, therefore, a tumour may grow too rapidly for the weakened immune system to cope thus increasing our risk of a cancer.

Since 1974, the increase of polyunsaturated fats has been blamed for the alarming increase in malignant melanoma (skin cancer) in Australia.

We are all told that the sun causes it.

Are Australians going out in the sun any more now than they were fifty years ago?

They are certainly eating more polyunsaturated oils: even milk has its cream removed and replaced with vegetable oil.

Victims of the disease have been found to have polyunsaturated oils in their skin cells.

Polyunsaturated oils are oxidised readily by ultra-violet radiation from the sun and form harmful 'free radicals'.

These are known to damage the cell's DNA and this can lead to the deregulation we call cancer.

Saturated fats are stable.

They do not oxidise and form free radicals.

Malignant melanoma is also said to be increasing in this country.

Does the sun cause this?

In Britain the number of sufferers is so small as to be relatively insignificant.

Even so, it is not likely that the sun is to blame since all the significant increase is in the over-seventy-five-year-olds.

People in this age group tend to get very little sun.

Melanoma occurs ten times as often in Orkney and Shetland than it does on Mediterranean islands.

It also occurs more frequently on areas that are not exposed to the sun.

In Scotland, for example, there are five times as many melanomas on the feet as on the hands; and in Japan, forty per cent of pedal melanomas are on the soles of the feet.

In 1991, two studies, from USA and Canada, found that linoleic acid, the major polyunsaturated fatty acid found in vegetable oils, increased the risk of breast tumours.

This, it seems, was responsible for the rise in the cancers noted in previous studies.

Experiments with a variety of fats showed that saturated fats did not cause tumours but, when small amounts of polyunsaturated vegetable oil or linoleic acid itself was added, this greatly increased the promotion of breast cancer.

A study of 61,471 women aged forty to seventy-six, conducted in Sweden, looked into the relation of different fats and breast cancer.

The results were published in January 1998.

This study found an inverse association with monounsaturated fat and a positive association with polyunsaturated fat.

In other words, monounsaturated fats protected against breast cancer and polyunsaturated fats increased the risk.

Saturated fats were neutral.

All polyunsaturated margarines, from the brand leader to shops 'own brands' are around thirty-nine percent linoleic acid.

Of cooking oils, sunflower oil is fifty percent and safflower oil seventy-two percent linoleic acid.

Butter, on the other hand, has only a mere two percent and lard is just nine percent linoleic acid.

Linoleic acid is one of the essential fatty acids.

We must eat some to live, but we do not need much.

The amount found in animal fats is quite sufficient.

Because of the heart disease risk, in 1994 the manufacturers of Flora changed its formula to cut out the trans fats and other manufacturers have since followed.

But that still leaves the linoleic acid.

The anti-cancer fat

Linoleic acid is one of the essential fatty acids that our bodies need but cannot synthesise.

We must eat some to survive.

Fortunately there is one form of linoleic acid that is beneficial.

Conjugated linoleic acid (CLA) differs from the normal form of linoleic acid only in the position of two of the bonds that join its atoms.

But this small difference has been shown to give it powerful anti-cancer properties.

Scientists at the Department of Surgical Oncology, Roswell Park Cancer Institute, New York and the Department of Biochemistry and Molecular Biology, New Jersey Medical School, showed that even at concentrations of less than one percent, CLA in the diet is protective against several cancers including breast cancer, colorectal cancer and malignant melanoma.

Conjugated linoleic acid has one other difference from the usual form - it is not found in vegetables but in the fat of ruminant animals.

The best sources are dairy products and the fat on red meat, principally beef.

It is another good reason not to give up eating red meat or to cut the fat off.

Scientists at the University of Wisconsin also believe that CLA has a slimming action.

They put the dramatic increase in obesity in the USA down to Americans not eating beef fat.

Monounsaturated fats

Several populations in the world, Eskimos and those in the Mediterranean countries for example, eat high-fat diets yet have very low incidences of heart disease.

This realisation has led to research scientists switching their attentions to monounsaturated fats found in fish oils and olive oil.

Although the supposed virtues of monounsaturated fats are being talked of in the press as possible saviours of Western man, the monounsaturated theory is not new.

It was first demonstrated over thirty years ago that giving people more unsaturated fats could lower blood cholesterol.

However, surveys of countries with different tastes in fats and oils have failed to show that this protects against heart disease.

For example, Norwegians, who eat a lot of saturated fats, have lower rates of the disease than New Zealanders who eat a similar amount.

But if, as has been suggested, the Norwegians are protected by the monounsaturated oils in the fish that they eat, then why is it that in Aberdeen, where a lot of fish is also consumed, the heart disease rate is double that of Oslo?

Proponents also forget that many other people, such as the Maasai tribes of Africa, who don't eat either fish or olive oil, also have a low incidence of heart disease.

(In This Blogger's Informed opinion They are not exposed to Chlorine!!! like the Scot's and the whole Western World)

There is also no evidence that either mono- or polyunsaturated oils are of benefit to those who have already suffered a heart attack.

As long ago as 1965 survival rates were studied in patients eating different oils.

Splitting patients into three groups, who were given polyunsaturated corn oil, monounsaturated olive oil and saturated animal fats respectively, it was found that only the corn oil lowered blood cholesterol levels.

At first sight, therefore, it seemed that men in the polyunsaturated group had the best chance of survival.

However, at the end of the two-year trial only fifty-two percent of the polyunsaturated corn oil group were still alive and free of a fresh heart attack.

Those on the monounsaturated olive oil fared little better: fifty-seven percent survived and had no further attack.

Those eating the saturated animal fats, however, fared much better with seventy-five percent surviving and without a further attack.

Breast Cancer.
The Swedish study by Alicia Wolk and colleagues mentioned above did find, however, that monounsaturated fats were protective against breast cancer.

Animal fats such as lard are around 43% Saturated, 47% Mono-unsaturated and 10% Polyunsaturated - which the evidence suggests is just about ideal.


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