Nutrition & Prostate Cancer

[Guest guest]

Nutrition & Prostate Cancer JoAnn Guest Apr 22, 2005 11:47 PDT

 

 

 

NOTES ON A TALK GIVEN BY ROY NIXON TO PSA NORTH WEST ON NUTRITION AND PROSTATE

CANCER ON 20.01.01 AT LEEDS

 

 

I began my talk by reminding the audience that I am not medically

qualified and that it is important to work in partnership with their

doctors. We looked at some of the possible reasons why men develop

prostate cancer. The reasons are,

of course many and varied and no one has a definitive answer. Here are some of

the reasons that are frequently suggested.

 

Aging

We know that the number of men under the age of 60 receiving a diagnosis of

prostate cancer has increased and continues to do so. Biopsies show latent

prostate cancer in men as young as 20 are fairly frequently discovered.

Microscopic traces of prostate cancer are present in 30% of men in their 50s and

70% in their 80s.

 

Race

There are differences in the incidence of prostate cancer in

geographical areas and in ethnic make-up. The risks are higher in North America

and Europe and lower in China and Japan.

 

African /American men are more likely to develop prostate cancer than white

American men, more likely to develop it at a younger

age and more likely to develop metastatic spread.

 

I asked people to consider the following questions as we progress with the talk.

" Is there a genetic predisposition among certain races? " and " Is it to do with

diet or other environmental factors? "

 

Genetic Factors

Those who have a father or brother who developed prostate cancer at an early age

are 2-3 times more likely to develop it themselves. Those who have a father and

a brother, or 2 brothers, with the disease at an early age have an even higher

risk (slightly) of developing the disease. About 9% of all prostate

cancer in the UK can be linked to genetic factors.

 

Environment

There is some evidence that men who work in the nuclear industry, or

have been exposed to cadmium, may have an increased risk of developing prostate

cancer.

Men living in the South of USA are at greater risk than men living in the North

and it is thought that this may be due to an increased level of ultra-violet

rays.

 

Diet

There is no overall agreement about the effects of diet on prostate

cancer, but there is a general acceptance that it may be an important factor. It

seems that fats may be of particular importance. I will discuss this in greater

detail at a later stage of the talk, but there are some contradictions that will

become apparent as we progress. The incidence of prostate cancer in Asia is much

lower than in the West.

 

In Asian countries there appears to be a higher ingestion of vitamin A.

 

I asked people to try to remember that when I discuss Beta-carotene later on.

Asian men, living in Asia, also tend to have a diet rich in phyto-oestrogens.

These are plant substances that imitate animal oestrogen and are found in soya

beans.

 

Recent research in the USA suggests that there may be an increased risk of

developing active prostate cancer in areas of low, or no selenium in the soil.

 

It would appear, therefore, that selenium may be an important factor.

 

The UK is an area that has very little selenium in its soil, probably because of

the high rainfall and soil erosion.

 

There is also a suggestion that vitamin E is of great

importance. Hormones Testosterone and dihydrotestosterone are essential for

healthy prostate growth. However, it also appears to play a part in the

development of prostate cancer. (In fact dihydrotestosterone is thought to be

more potent in 'feeding' prostate cancer than testosterone.) Men who

have been castrated in their youth almost never get the disease.

 

There appear to be a correlation between a raised enzyme

(5alpha-reductase) and the development of prostate cancer.

 

5alpha-reductase is involved with the conversion of testosterone to

dihydrotestosterone. Researchers are still looking

at the precise role of hormones and the development of prostate cancer.

 

Sexual behaviour

It has been suggested that men who develop prostate cancer have higher levels of

testosterone than other men and are therefore likely to be more sexually active.

 

It has also been suggested that men who become sexually active at an

early age (whatever that is?) or develop a sexually transmitted disease are at

greater risk.

 

I have not been able to find any conclusive evidence, although

there does appear to be a high correlation between high levels of testosterone

and prostate cancer, and men who produce high levels of testosterone are likely

to have a strong sexual appetite.

 

 

Vasectomy

It has been suggested that men who have a vasectomy are at greater risk. Again I

know of no research that supports this.

 

Diet revisited

I then went on to talk in greater detail about diet. The incidence of active

prostate cancer is lower in Asia than in the West. Death rates are 80% lower in

Japan and parts of China, although it is predicted that these countries will see

the largest increase as they move more and more towards a Western diet and

lifestyle.

 

It is known that when Japanese men move to the West they are just as likely to

develop active prostate cancer as Western men.

 

It is also known that Japanese men living in Japan are equally likely to develop

latent (slow growing) prostate cancer, but metastatic spread (secondary spread)

is less likely. The main difference between Japanese men and Western men, in

this respect seems to be in the levels of fat consumption.

 

In the West we get most of our fat through animal products like meat, cheese,

milk and also through fried foods and salad dressings.

 

In Japan fat is more likely to come from fish, rice and beans. What is less

clear is whether it is the type, or amount of fat that is the crucial factor.

 

Research may help to clear this up. One study involved 50,000 health

care professionals and the other involved 15,000 doctors.

 

What they found was that there was an increased risk of metastatic

spread amongst those who ate most animal fats.

 

One study in particular by E Giovannucu and his colleagues,(1) found

that the greatest risk of spread was from those who had the highest

concentrations of alpha-linolenic acid.

 

This is a polyunsaturated oil found in many vegetable cooking oils.

 

It is particularly high in flaxseed oil, which is often recommended to men with

prostate cancer by nutritional experts.

 

You must make up your own mind whether to use it or not.

 

The second study, by P.Gann et al, (2) showed that the fatty

acid stearic acid appeared to be associated with a 70% reduction of

risk.

 

As far as I know stearic acid is only found in cocoa butter and is high in

plain, dark chocolate that contains no milk. I eat organic plain chocolate,

although as with everything else, it is possible to have too much of a good

thing!

 

Red meat

 

We all need essential fatty acids in order to maintain good health. The fatty

acids that you are probably most aware of are omega 3 and omega 6. Most health

food shops sell capsules containing these essential fatty acids. A friend who is

an oncologist in the USA (Dr Charles " Snuffy " Myers)

tells me that it is very uncommon for an adult on an average American diet to

become deficient in fatty acid.

 

Too much of a certain kind of fatty acid (omega 6) can make you ill,

but it is thought that omega 3 fatty acids derived from fish oils may be

beneficial.

 

Risk Factors

 

 

Meat - especially red meat

Dairy fat

Salad dressings.

Animal fats

 

 

Arachidonic Acid - Present in all meat and dairy products. This fatty acid has

been shown to produce an increase in prostate cancer growth by stimulating an

increase in cancer cell blood vessels.

 

It can also cause damage to the immune system. Humans can also make our own

arachidonic acid, and the most efficient way of doing this is by converting

another essential fatty acid called linoleic acid to arachidonic acid.

 

Linoleic acid is present in all plant oils, but particularly high in flaxseed

oil. Vegans have been found to have between 10% and 30% less arachidonic acid

present than

meat eaters and this seems to suggest that we can reduce our levels of

arachidonic acid by considerably reducing, or eliminating meat and animal fat

products.

 

This is bad news for people who are big meat eaters!

 

Hormones revisited Arachidonic acid has been shown to convert to the

following hormones: 5-HETE; 12-HETE and PGE2 (prostaglandin) These are known to

be made by

prostate cancer cells and play a role in the spread of the disease.

 

Arachidonic acid stimulates the ability of prostate cancer cells to move and

invade.

 

This process requires the conversion of arachidonic acid to the hormone 12-HETE.

 

In 1995 Jagat Ghosh and Charles Myers (3) did an experiment with some prostate

cancer cells. They placed the cells in salt water and within 24 hours they died.

 

 

When they added arachidonic acid the cancer cells were able to survive and grow.

 

They discovered that 5-HETE played an important part in this process.

 

When they blocked the formation of 5-HETE the cells died within a few hours.

 

They concluded that the hormone 5-HETE switches off the 'suicide'

mechanism of cells and that when they deprived the cells of 5-HETE the 'suicide'

mechanism became deactivated.

 

I ended my talk by talking about the importance of the minerals selenium and

zinc, and the antioxidants vitamins A; C and E in the elimination of free

radicals, but mentioned that a Finnish study had thrown some doubt on the

benefits of beta-carotene, which converts to vitamin A.

 

I pointed out, however, that all the people involved in this study were smokers

and that this may have made a significant difference to the outcome. It may be

too soon to conclude that beta-carotene is not a helpful antioxidant for men

with prostate cancer.

 

Vitamin E appears to be a very effective antioxidant for men with

prostate cancer.

 

In a very large study of men who were smokers in Finland, carried out by

Vanrijn and Vandenberg, (4) men who were given vitamin E on its own were 32%

less likely to develop prostate cancer and 41% less likely to die from the

disease. It seems had to believe that vitamin E is only likely to be of value to

smokers.

 

Lycopene is another very important antioxidant that is found in

tomatoes. It is the part of the tomato that allows it to turn red. Lycopene is

thought to be beneficial for men with prostate cancer and is absorbed more

easilyif the tomatoes are cooked.

 

Its benefit seems to be in interrupting the ability of blood vessel

formation in cancer cells and tumours.

Genistein is found in soya beans and again is thought to be beneficial in a

similar way to lycopene.

 

Vitamin D - the sunshine vitamin - is important for the absorption of calcium.

Vitamin D3 may be of particular benefit to men who are on hormone

therapy, but this is only available on prescription and many doctors in the UK

remain unconvinced about benefits.

 

The mineral selenium is thought to be very important and, as much of the food we

eat is deficient in this mineral, the best source seems to be by supplement.

 

There is a need to be careful not to take selenium in high levels and people

should seek advice as to the safe level. Most health food stores sell selenium

at levels of 100 and 200 microgrammes and the higher level is thought to be a

maximum level for most people. Please tell your doctor if you are receiving

treatment and taking selenium.

 

Zinc Many people have asked about zinc over the past few weeks and

months, so here is the latest information I have on it. Zinc is known to play a

major part in the normal functioning of a healthy prostate.

 

It has a key role in helping the prostate to manufacture citric acid, which is a

major component of semen.

Unfortunately, prostate cancer cells do not accumulate zinc and

therefore do not make citric acid.

 

This allows cells to generate increased energy, which in turn encourages

prostate cancer cells to develop and spread.

 

Interestingly, although zinc protects most cells from apoptosis (cell death)

high levels of zinc have been shown to reduce the ability of cancer cells to

create new blood vessels.

It does this by causing a slight copper deficiency.

 

Copper is necessary for the formation of new blood vessels.

 

As cancer cells need a good supply of blood, reducing this can be beneficial.

When prostate cells become malignant they stop accumulating zinc and levels drop

by 80% - 90%. There

is some evidence that the intake of zinc can reduce the risk of men

developing prostate cancer.

 

I eat a handful of pumpkin seeds, which are high in zinc, everyday.

 

However I have no real idea of how much zinc I am actually getting and you may

prefer to take a supplement in tablet form. I am not allowed to recommend an

appropriate amount, but I am told that we can generally tolerate a dose somewhat

higher than the RDA (recommended daily allowance.)

 

Green Tea

Many people have now heard about possible benefits from drinking green tea. The

Mayo Clinic in the USA have done some research on this subject.

 

What they discovered in their laboratory is that a polyphenol in the tea called

epigallocatechin gallate (shortened to EPCg) had an impact on cancer cells, but

did not harm healthy cells.

 

It would seem that EPCg interacts with an enzyme called quinol oxidase

(shortened to NOX). NOX is required for growth in normal and cancerous cells,

but cancerous cells overproduce it.

 

It would seem that green tea interacts with NOX (in the laboratory) and appears

to play a part in blocking cell growth.

 

It has been suggested that between 6 and 8 cups of green tea per day may be

beneficial. Green tea tablets are also available from health food shops. We

should always bear in mind that laboratory experiments do not always transfer

successfully to the human body, but green tea may be helpful.

 

Conclusion

It would seem that the best diet would be one that contains little or no meat,

lots of fruit and vegetables, particularly dark green vegetables such as

 

broccoli, pasta, beans, garlic, tomatoes, grains and oats.

 

Extra Virgin Olive oil is the preferred oil.

 

Please remember that you will be able to absorb the genistein in tomatoes more

successfully if you cook them before

eating.

 

Those who eat a Mediterranean diet are said to have 50% fewer heart

attacks and

60% fewer cancers -7-

 

References: (1) E.Gioanucci, et al. 'A Prospective Study

of Dietary Fat and Risk of Prostate Cancer'. Journal of the National

Cancer

Institute 85: 1571 - 1579, 1993. (2) P.Gann, et al. Prospective Study of

Plasma

Fatty Acids and Risk of Prostate Cancer'. Journal of the National Cancer

 

Institute 86: 281 - 286, 1994. (3) J. Ghosh and Charles Myers.

'Arachidonic Acid

Stimulates Prostate cancer Cell Growth: Critical Role of 5-Lipoxygenase'

 

Biochemical and Biophysical Research Communications 235: 418 -423, 1997.

(4) J.

Vanrijn and J. Vandenberg. 'Flavonoids as Enhancers of X-ray-induced

Cell Damage

in Hepatoma Cells' Clinical Cancer Research 3: 1775 -1779, 1997.

 

 

Roy Nixon

http://www.yoogee.com/search/?lt=3 & q=5-HETE

_________________

 

JoAnn Guest

mrsjo-

DietaryTi-

www.geocities.com/mrsjoguest/Genes

 

 

 

 

AIM Barleygreen

" Wisdom of the Past, Food of the Future "

 

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