Polyunsaturated oils and cancer risk

[Guest guest]

Sun, 19 Jun 2005 11:23:45 -0000

" Naomi Giuliano " <n.giuliano

Polyunsaturated oils increase cancer risk

 

http://www.second-opinions.co.uk/fats_and_cancer.html

 

Introduction

 

Up to the 19th-century, fat was relatively expensive

and butter was a

luxury. The poor lived mainly on potatoes and bread,

which were cheap,

supplemented whenever possible with whatever source of

protein and fat

they could afford. Not surprisingly, mortality was

high amongst the

poorer classes. To fill the gap in the market cheap

substitutes for

butter began to be produced in the last quarter of the

Victorian era.

Made from cheaper fats and coloured yellow to mimic

the look, if not

the taste of butter, they were called margarine. And

this started,

quite slowly at first, a radical change in the types

of fat we, as a

nation, ate.

 

Originally margarines were made of beef suet, milk and

water. Later

the recipes changed to include lard, whale oil and the

oils of olive,

coconut, ground nut and cottonseed. By the middle of

the 20th-century

an emulsion of soya bean and water was substituted for

the milk and

margarines could be made entirely of inexpensive oils

from vegetable

sources. In all these forms, margarine was the poor

relation to

butter.

 

In the 1920s a new disease had suddenly 'taken off'

all over the

industrialised world. By the 1940s it had become a

leading cause of

premature death – and nobody knew why. In 1950, an

American

scientists

hypothesised that cholesterol might be to blame. (1)

In 1953, another

American, Ancel Keys, compared levels of this disease

in seven

countries with the amounts of fat in those countries.

(2) And so was

born the 'Diet-Heart' hypothesis, for the new disease

was coronary

heart disease.

 

To reduce the risk of a heart attack, Ancel Keys

recommended cutting

down on the vegetable oils and margarines. However, it

was discovered

that vegetable oils, which are composed largely of

unsaturated fats

and oils, tended to lower blood cholesterol levels,

while saturated

fats tended to raise them. And by that time, it had

been decided,

largely by majority vote, (3) that raised cholesterol

increased the

risk of a heart attack. With the advent of the

'Prudent Diet' in the

USA in 1982, and COMA's introduction of 'healthy

eating' in Britain

two years later, the fats in our diet changed even

more dramatically:

we were told to avoid animal fats such as butter and

lard, which have

a larger proportion of saturated fats, in favour of

largely

polyunsaturated vegetable margarines and cooking oils.

Now margarines

could be priced to rival butter. Recently, margarines

have been

developed specifically to lower cholesterol levels,

and prices have

risen again. Benecol, made from tree bark is

considerably more

expensive than butter.

 

Before going further, it might be as well for you to

learn a little

chemistry. This will make understanding how the

different fats react

under different circumstances. This is essential to

understanding how

cancers start or are promoted.

 

Margarine – a natural food?

 

The polyunsaturated fats used to make margarine are

generally obtained

from vegetable sources: sunflower seed, cottonseed,

and soybean. As

such they might be thought of as natural foods.

Usually, however, they

are pressed on the public in the form of highly

processed margarines,

spreads and oils and, as such, they are anything but

natural.

 

In 1989, the petroleum-based solvent, benzene, that is

known to cause

cancer, was found in Perrier mineral water at a mean

concentration of

fourteen parts per billion. This was enough to cause

Perrier to be

removed from supermarket shelves. The first process in

the manufacture

of margarine is the extraction of the oils from the

seeds, and this is

usually done using similar petroleum-based solvents.

Although these

are then boiled off, this stage of the process still

leaves about ten

parts per million of the solvents in the product. That

is 700 times as

much as fourteen parts per billion.

 

The oils then go through more than ten other

processes: degumming,

bleaching, hydrogenation, neutralization,

fractionation,

deodorisation, emulsification, interesterification, .

.. . that include

heat treatment at 140-160C with a solution of caustic

soda; the use of

nickel, a metal that is known to cause cancer, as a

catalyst, with up

to fifty parts per million of the nickel left in the

product; the

addition of antioxidants such as butylated

hydroxyanisol (E320). These

antioxidants are again usually petroleum based and are

widely believed

to cause cancer.

 

The hydrogenation process, that solidifies the oils so

that they are

spreadable, produces trans -fatty acids that rarely

occur in nature.

 

The heat treatment alone is enough to render these

margarines

nutritionally inadequate. When the massive chemical

treatment and

unnatural fats are added, the end product can hardly

be called either

natural or healthy.

 

You may be interested in a list of the ingredients

that may be present

in butter and margarine:

 

Butter:

milk fat (cream),

a little salt,

 

Margarine:

Edible oils,

edible fats,

salt or potassium chloride,

ascorbyl palmitate,

butylated hydroxyanisole,

phospholipids,

tert-butylhydroquinone,

mono- and di-glycerides of fat-forming fatty acids,

disodium guanylate,

diacetyltartaric and fatty acid esters of glycerol,

Propyl, octyl or dodecyl gallate (or mixtures

thereof),

tocopherols,

propylene glycol mono- and di-esters,

sucrose esters of fatty acids,

curcumin,

annatto extracts,

tartaric acid,

3,5,trimethylhexanal,

ß-apo-carotenoic acid methyl or ethyl ester,

skim milk powder,

xanthophylls,

canthaxanthin,

vitamins A and D.

 

Dietary fat patterns

 

The total amount of fats in our diet today, according

to the MAFF

National Food Survey, is almost the same as it was at

the beginning of

this century. What has changed, to some extent, is the

types of fats

eaten. At the turn of the century we ate mainly animal

fats that are

largely saturated and monounsaturated. Now we are

tending to eat more

polyunsaturated fats – it's what we are advised to do.

In 1991,

two

studies, from USA (4) and Canada, (5) 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.

 

Body cell walls are made of cholesterol, protein and

fats. The graph

below demonstrates that 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.

 

[chart]

 

Fatty acids in human fat

 

Polyunsaturated fats suppress the immune system

 

Polyunsaturated fats (PUFs) are greatly

immunosuppressive, and

anything that suppresses the immune system is likely

to cause cancer.

The first person to suggest that polyunsaturated fats

cause cancer was

Dr R A Newsholme of Oxford University, England. (6)

What Newsholme

wrote was that when our bodies get sufficient

nutrition, our diet

includes immunosuppressive PUFs which make us prone to

infection by

bacteria and viruses. When we are starved, however,

our body stores of

PUFs are depleted. This allows our bodies' immune

systems to recover

which, in turn, allows us to fight existing infection

and prevent

other infections. He was making the point that the

immunosuppressive

effects of PUFs in sunflower seeds are useful in

treating autoimmune

diseases such as multiple sclerosis, (7) and that the

same fatty acids

could be used to suppress the immune system to prevent

rejection of

kidney transplants.

 

It was during the early days of kidney transplantation

that doctors

first encountered the problem of tissue rejection as

their patients'

bodies destroyed the alien transplanted kidneys. If

transplantation

were to be a success, they had to find a way to

suppress the immune

system. Newsholme had said that there was no better

way to

immunosuppress a renal patient than with sunflower

seed oil. So kidney

transplant doctors fed their patients linoleic acid.

(8) (Linoleic

acid is the major polyunsaturated fatty acid in

vegetable oils.) But

the transplant doctors were then astonished to see how

quickly their

patients developed cancers: some cancers were up to

twenty times as

frequent as was expected.

 

This was in line with heart trials using diets that

were high in PUFs

which, reported an excess of cancer deaths from as

early as 1971. (9)

 

By the early 1980s, we were being exhorted by doctors

and

nutritionists to eat more PUFs because they were 'good

for us' despite

the fact that Oncology Times carried a paper in

January 1980 from the

University of California at Davis that mice fet PUFs

were more prone

to develop melanoma. In May 1980, the same publication

carried a

similar report from Oregon State University which said

that PUFs fed

to cancer-prone mice increased the numbers of cancers

formed.

 

In 1989 there was a report of a ten-year trial at a

Veterans'

Administration Hospital in Los Angeles. In this trial

half the

patients were fed a diet which had double the amount

of PUFs as

compared to saturated fats. In the half of the

patients on the high

PUF diet there was a fifteen percent increase in

cancer deaths

compared to the saturated fat group. (10) The authors

of the report

said that the PUFs had been the cause of the increase

in cancer

deaths. The British Medical Journal carried an

editorial in its 6

October 1973 issue which asked if PUFs were

carcinogenic. It came to

the conclusion that they were.

 

Wayne Martin likes to tell a story which suggests just

how

cancer-causing are PUFs. In 1930 in the USA, eighty

percent of men

smoked cigarettes and the tar content of cigarettes

was much higher

than it is today. The death rate at that time from

lung cancer was

very low. In 1955 doctors decided that PUFs were good

in terms of

heart disease protection. After this lung cancer

deaths increased so

dramatically. By 1980 although the number of American

men who smoked

had dropped to only thirty percent, three times as

much PUF was being

eaten – and there were sixty times as many lung cancer

deaths.

(11)

 

In 1990, Martin called Newsholme's Oxford University

office but by

then Newsholme had retired. Martin spoke to his

successor to find that

they were still treating autoimmune diseases with

PUFs. By then they

were using fish oil. The doctor said the reason for

the fish oil was

that the degree of immunosuppression increased with

the degree of

unsaturation and fish oil was much more unsaturated

than sunflower

oil. Martin asked the doctor why they were not talking

about PUFs

causing cancer. The doctor replied that if he did that

he would be run

out of Oxford.

 

Carcinogens – background radiation, ultraviolet

radiation from the

sun, particles in the air we breathe 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. 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.

 

Polyunsaturated fats cause cancer

 

Since 1974, the increase of polyunsaturated fats has

been blamed for

the alarming increase in malignant melanoma (skin

cancer) in

Australia. (12) 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: in

Australia in 1995 I saw that even the cream on milk

was 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.

 

That the sun is not to blame is confirmed by other

findings:

 

* 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 . (13)

 

Polyunsaturated fats promote cancer

 

Many laboratories have shown that diets high in

polyunsaturated fatty

acids promote tumours. Cancer promotion is not the

same as cancer

causing. The subject is complex; suffice to say here

that promoters

are substances that help to speed up reproduction of

existing cancer

cells.

 

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: 'Many laboratories have

shown that a

greater proportion of polyunsaturated fats are

superior to diets rich

in saturated fats in promoting the yield of

experimental mammary

tumours. In such studies, omega-6 linoleic acid

appeared to be the

crucial fatty acid . . .' and 'Vegetable oils (eg Corn

oil and

sunflower oil) which are rich in linoleic acid are

potent promoters of

tumour growth.' (14)

 

Polyunsaturated fats and 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. (15)

 

Flora margarine, the brand leader, is thirty-nine

percent linoleic

acid; Vitalite and other 'own brand' polyunsaturated

margarines are

similar. 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 in animal

fats is quite

sufficient.

 

Because of the heart disease risk from trans-fats in

margarines, 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 (16) and the Department of

Biochemistry and

Molecular Biology, New Jersey Medical School, (17)

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. (18)

 

It has been suggested that the consumption of red meat

increases the

risk of colon cancer, yet in Britain there is no

evidence to support

this. (19) It is interesting that all the evidence

implicating red

meat in cancer comes from the USA – where they cut the

fat off.

 

Conclusions

 

Saturated fats and animal fats are usually blamed for

all manner of

diseases in Western society. But look at the facts:

 

* In the 19th-century, when animal fats were all

that was

available, cancers were rare (as was heart disease).

* Polyunsaturated fats and oils are used to

suppress the immune

system, such immunosuppression is known to cause

cancers to start and

promote cancer.

* In this last century there has been a change in

favour of

polyunsaturated fats and oils – and cancer rates have

soared.

 

Unfortunately, as polyunsaturated fatty acids are also

essential to

the body; we must have some. So a proper balance must

be struck.

Whether the dramatic increase in the numbers of

cancers in the last

century was as a result of a similarly dramatic rise

in our intake of

polyunsaturated vegetable oils is not known – but the

evidence

strongly favours such a conclusion.

 

Under the circumstances, it seems prudent to get what

linoleic acid we

need from animal sources. Or to restrict

polyunsaturated oil

consumption so that linoleic acid is no more than

three percent of the

total fat intake.

 

References

 

1. Gofman, J W, et al. The role of lipids and

lipoproteins in

atherosclerosis. Science 1950; 111: 166-181, 186

 

2. Keys A. Atherosclerosis: a problem in newer public

health. J Mt

Sinai Hosp 1953; 20: 118-139.

 

3. Mann G V. Diet-heart: End of an Era. New Eng J Med

.. 1977; 297:

644.

 

4. Carroll K K. Dietary fats and cancer. Am J Clin

Nutr 1991; 53:

1064S.

 

5. France T, Brown P. Test-tube cancers raise doubts

over fats. New

Scientist , 7 December 1991, p 12.

 

6. Newsholme E A. Mechanism for starvation suppression

and refeeding

activity of infection. Lancet 1977; i: 654.

 

7. Miller JD, et al. Br Med J 1973; i: 765.

 

8. Uldall PR, et al . Lancet 1974; ii: 514.

 

9. Pearce M L, Dayton S. Incidence of cancer in men on

a diet high in

polyunsaturated fat. Lancet 1971; i: 464.

 

10. American Heart Association Monograph, No 25. 1969.

 

11. Nauts HC. Cancer Research Institute Monograph No

18. 1984, p 91.

 

12. Mackie BS. Med J Austr 1974; 1: 810.

 

13. Karnauchow PN. Melanoma and sun exposure. Lancet

1995; 346: 915.

 

14. Kearney R. Promotion and prevention of tumour

growth –

effects of

endotoxin, inflammation and dietary lipids. Int Clin

Nutr Rev 1987; 7:

157.

 

15. Wolk A, et al. A Prospective Study of Association

of

Monounsaturated Fat and Other Types of Fat With Risk

of Breast Cancer.

Arch Intern Med . 1998; 158: 41-45

 

16. Ip C, Scimeca J A, Thompson H J. Conjugated

linoleic acid. A

powerful anticarcinogen from animal fat sources.

Cancer 1994; 74(3

Suppl): 1050-4.

 

17. Shultz T D, Chew B P, Seaman W R, Luedecke L O.

Inhibitory effect

of conjugated dienoic derivatives of linoleic acid and

beta-carotene

on the in vitro growth of human cancer cells. Cancer

Letters 1992; 63:

125-133.

 

18. Lin H, Boylston TD, Chang MJ, Luedecke LO, Schultz

TD. Survey of

the conjugated linoleic acid contents of dairy

products. J Dairy Sci .

1995; 78: 2358-65.

 

19. Cox BD, Whichelow MJ. Frequent consumption of red

meat is not a

risk factor for cancer. Br Med J 1997; 315: 1018.

 

 

 

 

 

 

 

__________________________

[Guest guest]

I have always maintained that real butter is alot healthier for you than margerines, despite what we've been told for years now - to stay away from butter.

 

Blessings, Renee"Kelly W." <kellykebby wrote:

Sun, 19 Jun 2005 11:23:45 -0000 "Naomi Giuliano" <n.giulianoPolyunsaturated oils increase cancer riskhttp://www.second-opinions.co.uk/fats_and_cancer.html IntroductionUp to the 19th-century, fat was relatively expensiveand butter was aluxury. The poor lived mainly on potatoes and bread,which were cheap,supplemented whenever possible with whatever source ofprotein and fatthey could afford. Not surprisingly, mortality washigh amongst thepoorer classes. To fill the gap in the market cheapsubstitutes forbutter began to be produced in the last quarter of theVictorian era.Made from cheaper fats and coloured yellow to mimicthe look, if notthe taste of butter, they were

called margarine. Andthis started,quite slowly at first, a radical change in the typesof fat we, as anation, ate.Originally margarines were made of beef suet, milk andwater. Laterthe recipes changed to include lard, whale oil and theoils of olive,coconut, ground nut and cottonseed. By the middle ofthe 20th-centuryan emulsion of soya bean and water was substituted forthe milk andmargarines could be made entirely of inexpensive oilsfrom vegetablesources. In all these forms, margarine was the poorrelation tobutter.In the 1920s a new disease had suddenly 'taken off'all over theindustrialised world. By the 1940s it had become aleading cause ofpremature death – and nobody knew why. In 1950, anAmericanscientistshypothesised that cholesterol might be to blame. (1)In 1953, anotherAmerican, Ancel Keys, compared levels of this diseasein sevencountries with the amounts of

fat in those countries.(2) And so wasborn the 'Diet-Heart' hypothesis, for the new diseasewas coronaryheart disease.To reduce the risk of a heart attack, Ancel Keysrecommended cuttingdown on the vegetable oils and margarines. However, itwas discoveredthat vegetable oils, which are composed largely ofunsaturated fatsand oils, tended to lower blood cholesterol levels,while saturatedfats tended to raise them. And by that time, it hadbeen decided,largely by majority vote, (3) that raised cholesterolincreased therisk of a heart attack. With the advent of the'Prudent Diet' in theUSA in 1982, and COMA's introduction of 'healthyeating' in Britaintwo years later, the fats in our diet changed evenmore dramatically:we were told to avoid animal fats such as butter andlard, which havea larger proportion of saturated fats, in favour oflargelypolyunsaturated vegetable margarines and

cooking oils.Now margarinescould be priced to rival butter. Recently, margarineshave beendeveloped specifically to lower cholesterol levels,and prices haverisen again. Benecol, made from tree bark isconsiderably moreexpensive than butter.Before going further, it might be as well for you tolearn a littlechemistry. This will make understanding how thedifferent fats reactunder different circumstances. This is essential tounderstanding howcancers start or are promoted.Margarine – a natural food?The polyunsaturated fats used to make margarine aregenerally obtainedfrom vegetable sources: sunflower seed, cottonseed,and soybean. Assuch they might be thought of as natural foods.Usually, however, theyare pressed on the public in the form of highlyprocessed margarines,spreads and oils and, as such, they are anything butnatural.In 1989, the petroleum-based solvent,

benzene, that isknown to causecancer, was found in Perrier mineral water at a meanconcentration offourteen parts per billion. This was enough to causePerrier to beremoved from supermarket shelves. The first process inthe manufactureof margarine is the extraction of the oils from theseeds, and this isusually done using similar petroleum-based solvents.Although theseare then boiled off, this stage of the process stillleaves about tenparts per million of the solvents in the product. Thatis 700 times asmuch as fourteen parts per billion.The oils then go through more than ten otherprocesses: degumming,bleaching, hydrogenation, neutralization,fractionation,deodorisation, emulsification, interesterification, .. . that includeheat treatment at 140-160C with a solution of causticsoda; the use ofnickel, a metal that is known to cause cancer, as acatalyst, with upto fifty parts per

million of the nickel left in theproduct; theaddition of antioxidants such as butylatedhydroxyanisol (E320). Theseantioxidants are again usually petroleum based and arewidely believedto cause cancer.The hydrogenation process, that solidifies the oils sothat they arespreadable, produces trans -fatty acids that rarelyoccur in nature.The heat treatment alone is enough to render thesemargarinesnutritionally inadequate. When the massive chemicaltreatment andunnatural fats are added, the end product can hardlybe called eithernatural or healthy.You may be interested in a list of the ingredientsthat may be presentin butter and margarine:Butter:milk fat (cream),a little salt,Margarine:Edible oils,edible fats,salt or potassium chloride,ascorbyl palmitate,butylated hydroxyanisole,phospholipids,tert-butylhydroquinone,mono- and di-glycerides of

fat-forming fatty acids,disodium guanylate,diacetyltartaric and fatty acid esters of glycerol,Propyl, octyl or dodecyl gallate (or mixturesthereof),tocopherols,propylene glycol mono- and di-esters,sucrose esters of fatty acids,curcumin,annatto extracts,tartaric acid,3,5,trimethylhexanal,ß-apo-carotenoic acid methyl or ethyl ester,skim milk powder,xanthophylls,canthaxanthin,vitamins A and D.Dietary fat patternsThe total amount of fats in our diet today, accordingto the MAFFNational Food Survey, is almost the same as it was atthe beginning ofthis century. What has changed, to some extent, is thetypes of fatseaten. At the turn of the century we ate mainly animalfats that arelargely saturated and monounsaturated. Now we aretending to eat morepolyunsaturated fats – it's what we are advised to do.In 1991,twostudies, from USA (4) and Canada, (5) found

thatlinoleic acid, themajor polyunsaturated fatty acid found in vegetableoils, increasedthe risk of breast tumours. This, it seems, wasresponsible for therise in the cancers noted in previous studies.Experiments with avariety of fats showed that saturated fats did notcause tumours but,when small amounts of polyunsaturated vegetable oil orlinoleic aciditself was added, this greatly increased the promotionof breastcancer.Body cell walls are made of cholesterol, protein andfats. The graphbelow demonstrates that the human body's fat make-upis largely ofsaturated and monounsaturated fatty acids. We containvery littlepolyunsaturated fat. Cell walls have to allow thevarious nutrientsthat body cells need from the blood, but stop harmfulpathogens. Theymust be stable. An intake of large quantities ofpolyunsaturated fattyacids changes the constituency of cholesterol and bodyfat.

Cell wallsbecome softer and more unstable.[chart]Fatty acids in human fatPolyunsaturated fats suppress the immune systemPolyunsaturated fats (PUFs) are greatlyimmunosuppressive, andanything that suppresses the immune system is likelyto cause cancer.The first person to suggest that polyunsaturated fatscause cancer wasDr R A Newsholme of Oxford University, England. (6)What Newsholmewrote was that when our bodies get sufficientnutrition, our dietincludes immunosuppressive PUFs which make us prone toinfection bybacteria and viruses. When we are starved, however,our body stores ofPUFs are depleted. This allows our bodies' immunesystems to recoverwhich, in turn, allows us to fight existing infectionand preventother infections. He was making the point that theimmunosuppressiveeffects of PUFs in sunflower seeds are useful intreating autoimmunediseases such as multiple

sclerosis, (7) and that thesame fatty acidscould be used to suppress the immune system to preventrejection ofkidney transplants.It was during the early days of kidney transplantationthat doctorsfirst encountered the problem of tissue rejection astheir patients'bodies destroyed the alien transplanted kidneys. Iftransplantationwere to be a success, they had to find a way tosuppress the immunesystem. Newsholme had said that there was no betterway toimmunosuppress a renal patient than with sunflowerseed oil. So kidneytransplant doctors fed their patients linoleic acid.(8) (Linoleicacid is the major polyunsaturated fatty acid invegetable oils.) Butthe transplant doctors were then astonished to see howquickly theirpatients developed cancers: some cancers were up totwenty times asfrequent as was expected.This was in line with heart trials using diets thatwere high in

PUFswhich, reported an excess of cancer deaths from asearly as 1971. (9)By the early 1980s, we were being exhorted by doctorsandnutritionists to eat more PUFs because they were 'goodfor us' despitethe fact that Oncology Times carried a paper inJanuary 1980 from theUniversity of California at Davis that mice fet PUFswere more proneto develop melanoma. In May 1980, the same publicationcarried asimilar report from Oregon State University which saidthat PUFs fedto cancer-prone mice increased the numbers of cancersformed.In 1989 there was a report of a ten-year trial at aVeterans'Administration Hospital in Los Angeles. In this trialhalf thepatients were fed a diet which had double the amountof PUFs ascompared to saturated fats. In the half of thepatients on the highPUF diet there was a fifteen percent increase incancer deathscompared to the saturated fat group. (10) The

authorsof the reportsaid that the PUFs had been the cause of the increasein cancerdeaths. The British Medical Journal carried aneditorial in its 6October 1973 issue which asked if PUFs werecarcinogenic. It came tothe conclusion that they were.Wayne Martin likes to tell a story which suggests justhowcancer-causing are PUFs. In 1930 in the USA, eightypercent of mensmoked cigarettes and the tar content of cigaretteswas much higherthan it is today. The death rate at that time fromlung cancer wasvery low. In 1955 doctors decided that PUFs were goodin terms ofheart disease protection. After this lung cancerdeaths increased sodramatically. By 1980 although the number of Americanmen who smokedhad dropped to only thirty percent, three times asmuch PUF was beingeaten – and there were sixty times as many lung cancerdeaths.(11)In 1990, Martin called Newsholme's Oxford

Universityoffice but bythen Newsholme had retired. Martin spoke to hissuccessor to find thatthey were still treating autoimmune diseases withPUFs. By then theywere using fish oil. The doctor said the reason forthe fish oil wasthat the degree of immunosuppression increased withthe degree ofunsaturation and fish oil was much more unsaturatedthan sunfloweroil. Martin asked the doctor why they were not talkingabout PUFscausing cancer. The doctor replied that if he did thathe would be runout of Oxford.Carcinogens – background radiation, ultravioletradiation from thesun, particles in the air we breathe and the food weeat –continuallyattack us all. Normally, the immune system deals withany small focusof cancer cells so formed and that is the end of it.But linoleic acidsuppresses the immune system. With a high intake ofmargarine,therefore, a tumour may grow too rapidly for

theweakened immunesystem to cope thus increasing our risk of a cancer.Polyunsaturated fats cause cancerSince 1974, the increase of polyunsaturated fats hasbeen blamed forthe alarming increase in malignant melanoma (skincancer) inAustralia. (12) We are all told that the sun causesit. AreAustralians going out in the sun any more now thanthey were fiftyyears ago? They are certainly eating morepolyunsaturated oils: inAustralia in 1995 I saw that even the cream on milkwas removed andreplaced with vegetable oil. Victims of the diseasehave been found tohave polyunsaturated oils in their skin cells.Polyunsaturated oilsare oxidised readily by ultra-violet radiation fromthe sun and formharmful 'free radicals'. These are known to damage thecell's DNA andthis can lead to the deregulation we call cancer.Saturated fats arestable. They do not oxidise and form free

radicals.Malignant melanoma is also said to be increasing inthis country. Doesthe sun cause this? In Britain the number of sufferersis so small asto be relatively insignificant. Even so, it is notlikely that the sunis to blame since all the significant increase is intheover-seventy-five-year-olds. People in this age grouptend to get verylittle sun.That the sun is not to blame is confirmed by otherfindings: * Melanoma occurs ten times as often in Orkney andShetland thanit does on Mediterranean islands. * It also occurs more frequently on areas that arenot exposed tothe sun. * In Scotland, for example, there are five timesas many melanomason the feet as on the hands; * and in Japan, forty per cent of pedal melanomasare on the solesof the feet . (13)Polyunsaturated fats promote cancerMany

laboratories have shown that diets high inpolyunsaturated fattyacids promote tumours. Cancer promotion is not thesame as cancercausing. The subject is complex; suffice to say herethat promotersare substances that help to speed up reproduction ofexisting cancercells.It has been known since the early 1970s that it islinoleic acid thatis the major culprit. As Professor Raymond Kearney ofSydneyUniversity put it in 1987: 'Many laboratories haveshown that agreater proportion of polyunsaturated fats aresuperior to diets richin saturated fats in promoting the yield ofexperimental mammarytumours. In such studies, omega-6 linoleic acidappeared to be thecrucial fatty acid . . .' and 'Vegetable oils (eg Cornoil andsunflower oil) which are rich in linoleic acid arepotent promoters oftumour growth.' (14)Polyunsaturated fats and breast cancerA study of 61,471 women aged forty to

seventy-six,conducted inSweden, looked into the relation of different fats andbreast cancer.The results were published in January 1998. This studyfound aninverse association with monounsaturated fat and apositiveassociation with polyunsaturated fat. In other words,monounsaturatedfats protected against breast cancer andpolyunsaturated fatsincreased the risk. Saturated fats were neutral. (15)Flora margarine, the brand leader, is thirty-ninepercent linoleicacid; Vitalite and other 'own brand' polyunsaturatedmargarines aresimilar. Of cooking oils, sunflower oil is fiftypercent and saffloweroil seventy-two percent linoleic acid. Butter, on theother hand, hasonly a mere two percent and lard is just nine percentlinoleic acid.Linoleic acid is one of the essential fatty acids. Wemust eat some tolive, but we do not need much. The amount in animalfats is

quitesufficient.Because of the heart disease risk from trans-fats inmargarines, in1994 the manufacturers of Flora changed its formula tocut out thetrans fats and other manufacturers have sincefollowed. But that stillleaves the linoleic acid.The anti-cancer fatLinoleic acid is one of the essential fatty acids thatour bodies needbut cannot synthesise. We must eat some to survive.Fortunately thereis one form of linoleic acid that is beneficial.Conjugated linoleicacid (CLA) differs from the normal form of linoleicacid only in theposition of two of the bonds that join its atoms. Butthis smalldifference has been shown to give it powerfulanti-cancer properties.Scientists at the Department of Surgical Oncology,Roswell Park CancerInstitute, New York (16) and the Department ofBiochemistry andMolecular Biology, New Jersey Medical School, (17)showed that even

atconcentrations of less than one percent, CLA in thediet is protectiveagainst several cancers including breast cancer,colorectal cancer andmalignant melanoma.Conjugated linoleic acid has one other difference fromthe usual form– it is not found in vegetables but in the fat ofruminantanimals.The best sources are dairy products and the fat on redmeat,principally beef. (18)It has been suggested that the consumption of red meatincreases therisk of colon cancer, yet in Britain there is noevidence to supportthis. (19) It is interesting that all the evidenceimplicating redmeat in cancer comes from the USA – where they cut thefat off.ConclusionsSaturated fats and animal fats are usually blamed forall manner ofdiseases in Western society. But look at the facts: * In the 19th-century, when animal fats were allthat wasavailable, cancers were rare

(as was heart disease). * Polyunsaturated fats and oils are used tosuppress the immunesystem, such immunosuppression is known to causecancers to start andpromote cancer. * In this last century there has been a change infavour ofpolyunsaturated fats and oils – and cancer rates havesoared.Unfortunately, as polyunsaturated fatty acids are alsoessential tothe body; we must have some. So a proper balance mustbe struck.Whether the dramatic increase in the numbers ofcancers in the lastcentury was as a result of a similarly dramatic risein our intake ofpolyunsaturated vegetable oils is not known – but theevidencestrongly favours such a conclusion.Under the circumstances, it seems prudent to get whatlinoleic acid weneed from animal sources. Or to restrictpolyunsaturated oilconsumption so that linoleic acid is no more thanthree percent of

thetotal fat intake.References1. Gofman, J W, et al. The role of lipids andlipoproteins inatherosclerosis. Science 1950; 111: 166-181, 1862. Keys A. Atherosclerosis: a problem in newer publichealth. J MtSinai Hosp 1953; 20: 118-139.3. Mann G V. Diet-heart: End of an Era. New Eng J Med. 1977; 297:644.4. Carroll K K. Dietary fats and cancer. Am J ClinNutr 1991; 53:1064S.5. France T, Brown P. Test-tube cancers raise doubtsover fats. NewScientist , 7 December 1991, p 12.6. Newsholme E A. Mechanism for starvation suppressionand refeedingactivity of infection. Lancet 1977; i: 654.7. Miller JD, et al. Br Med J 1973; i: 765.8. Uldall PR, et al . Lancet 1974; ii: 514.9. Pearce M L, Dayton S. Incidence of cancer in men ona diet high inpolyunsaturated fat. Lancet 1971; i: 464.10. American Heart Association Monograph, No 25. 1969.11. Nauts

HC. Cancer Research Institute Monograph No18. 1984, p 91.12. Mackie BS. Med J Austr 1974; 1: 810.13. Karnauchow PN. Melanoma and sun exposure. Lancet1995; 346: 915.14. Kearney R. Promotion and prevention of tumourgrowth –effects ofendotoxin, inflammation and dietary lipids. Int ClinNutr Rev 1987; 7:157.15. Wolk A, et al. A Prospective Study of AssociationofMonounsaturated Fat and Other Types of Fat With Riskof Breast Cancer.Arch Intern Med . 1998; 158: 41-4516. Ip C, Scimeca J A, Thompson H J. Conjugatedlinoleic acid. Apowerful anticarcinogen from animal fat sources.Cancer 1994; 74(3Suppl): 1050-4.17. Shultz T D, Chew B P, Seaman W R, Luedecke L O.Inhibitory effectof conjugated dienoic derivatives of linoleic acid andbeta-caroteneon the in vitro growth of human cancer cells. CancerLetters 1992; 63:125-133.18. Lin H, Boylston TD, Chang MJ,

Luedecke LO, SchultzTD. Survey ofthe conjugated linoleic acid contents of dairyproducts. J Dairy Sci .1995; 78: 2358-65.19. Cox BD, Whichelow MJ. Frequent consumption of redmeat is not arisk factor for cancer. Br Med J 1997; 315: 1018. __________________________

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