Selenium

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Selenium: Functions and Uses

 

Selenium: Functions and Uses JoAnn Guest Jun 13,

2005 18:04 PDT

 

 

http://www.willner.com/article.aspx?artid=182

Selenium

Selenium is present in all the tissues of the body,

but is concentrated

most highly in the kidneys, liver, spleen, pancreas,

and testes. People

do not consume enough selenium both because of the

type of diet they

eat, and because of the low selenium content of the

soil in which their

food is grown. The selenium content of soil varies

widely, with many

areas showing serious depletion. In fact, there have

been several

reports of selenium deficiencies in livestock raised

on

selenium-depleted soil.

 

FUNCTIONS AND USES

 

Cancer

 

Selenium’s best-known and perhaps most important

biological function

relates to its role as an antioxidant and anticancer

mineral. As we

have

seen in other chapters, free radicals damage our

cells, possibly

leading

to the development of cancer and other degenerative

diseases. Selenium

is an activating component of the enzyme glutathione

peroxidase, which

protects our cells from this damage.

 

Many animal studies have proven that selenium

deficiency increases the

incidence and rate of growth of cancers in animals

that are either

exposed to a variety of potent carcinogens or receive

transplanted

tumors. Companion studies have shown that high

selenium intake protects

against these cancers. For example, in one study in

which rats were

exposed to a potent carcinogen, only 15 percent of

those who were also

given selenium developed liver cancer as compared with

90 percent of

the

unsupplemented rats. In another study, the occurrence

of cancer was 10

percent in the supplemented group versus 80 percent in

the control

group. In yet another animal study, selenium

supplementation reduced

colon cancer incidence by more than 50 percent. In

another study,

selenium protected against UV-induced skin damage and

cancer, retarding

the onset and number of skin lesions, and reducing

inflammation,

blistering, and pigmentation.

 

In. humans, there is ample epidemiological evidence

that high selenium

is correlated with a lower incidence of many types of

cancer. For

instance researchers have found that cancer risk is

significantly lower

in people living in areas with selenium-rich soil, in

people with a

high-selenium food supply, and in people with higher

blood levels of

selenium, when compared with people with lower intakes

and blood

levels.

Selenium intakes in the people studied were close to

750 micrograms per

day, with no toxic side effects noted. In a survey

that spanned

twenty-seven countries, including the United States,

it was found that

the cancer death rate was lower in those people whose

typical diets

were

high in selenium. This and other cancer studies

indicate that selenium

is especially protective against cancer of the breast,

colon, and lung.

Data also suggests protection against tumors of the

ovaries, cervix,

rectum, bladder, esophagus, pancreas, skin, liver, and

prostate, as

well

as against leukemia.

 

 

 

Since 1969, it has been known that the blood levels of

cancer patients

are low in selenium. In general, cancer patients with

lower-than-average

selenium levels have a greater number of primary

tumors, more

recurrences, more distant metastases (tumors that have

spread to

distant

parts of the body), and a shortened survival time. In

a study of 12,000

people conducted in Finland, the risk of fatal cancer

in people with

the

lowest levels of serum selenium was nearly six times

higher than that

in

people with the highest selenium concentrations.

 

Like other nutrients, of course, selenium cannot do

its work alone. In

several studies, it has been shown that selenium and

vitamin E-and

perhaps vitamin A, too—have a synergistic effect. For

example, in one

study, male smokers who died of cancer had lower

levels of serum

selenium, vitamin A, and vitamin E, when compared with

healthy control

subjects. It is well known that vitamin E enhances the

antioxidant

effect of selenium. In. addition, it has been found

that

supplementation

with selenium alone and with selenium plus vitamin E

in excess of the

RDAs stimulates the immune system in experimental

animals. This effect

is particularly pronounced when the diet is high in

polyunsaturated

fats-a factor that has been linked to a higher

incidence of certain

cancers.

 

These studies show promise for the prevention and

possible treatment of

cancer with selenium supplementation. When combined

with other

supplements, the anticancer effect may be even

greater. The National

Cancer Inistitute is conducting ongoing

" chemopreventive " trials of

several individual nutrients, including selenium,

vitamin E, and

vitamin

A. However, often these trials are limited to 200

micrograms of

selenium

per day, which may be too low a dose to assess the

potential protective

effect of this mineral. Larger doses of selenium have

been shown to be

protective in animals, and safe in humans. In

addition, we are not sure

of the extent to which selenium supplementation

influences the later

stages of cancer development. If its influence is

strongest in the

early

stage, it will be very difficult for these trials to

prove the

connection between low selenium and cancer because of

the long latency

period for most cancers. (For example, it may take up

to fourteen years

for a single breast cancer cell to multiply and

produce a tumor large

enough to be detected by currently available

diagnostic methods.)

Finally, evidence of the synergism of nutrients has

led many

researchers

to emphasize the need to consider several nutrients in

any given diet

and cancer study, instead of focusing on just one

nutrient per study.

 

Cardiovascular Disease

 

In humans, a link has been found between selenium and

heart disease.

People found to have overt selenium

deficiencies-alcoholics with

cirrhosis of the liver, and people receiving long-term

intravenous

feeding-have also been found to suffer from heart

problems that respond

to selenium supplementation. In eastern Finland, which

has one of the

highest mortality rates from heart disease in the

world, it was found

that low selenium in the blood was associated with up

to a six- or

sevenfold increase in the risk of death from heart

disease. In

addition,

children in certain areas of China in which the

selenium content of the

soil is low are known to develop a heart disease

called Keshan’s

disease. Their heart problems, too, respond to

selenium

supplementation.

 

Other Functions

 

There is some evidence that selenium may also prove

effective in the

treatment or prevention of several other disorders. A

study using 400

micrograms of selenium and approximately 25

international units of

vitamin E markedly improved skin conditions such as

acne and seborrheic

dermatitis in the test subjects. A Danish study

examined patients with

rheumatoid arthritis and found that they had lower

levels of selenium.

Those with the lowest levels had the more severe form

of this disease.

Moreover, a recent study conducted in Japan suggests

that selenium and

vitamin E may enhance the responsiveness of arthritis

patients to

conventional treatment. A fascinating study conducted

in Scandinavia

showed a correlation between low selenium levels and

the incidence and

severity of muscular dystrophy; one patient who was

treated with

selenium supplements showed considerable improvement

after one year.

Finnish researchers have also conducted a study on

elderly patients,

who

were given large doses of selenium and vitamin E for

one year. After

two

months, researchers found an obvious improvement in

their patients’

mental well-being, including less fatigue, depression,

and anxiety, and

more mental alertness, motivation, and self-care.

Finally, selenium has

been shown to protect against the toxic effects of

mercury, arsenic,

and

copper.

 

RDIs AND DEFICIENCY SYMPTOMS

 

Selenium deficiency symptoms may include muscular

weakness and

discomfort. Recent studies have shown that people with

celiac

disease-an

inborn inability to digest glutenare at high risk for

low selenium,

along with other nutrients, either because their

lowgluten diets are

also low in selenium, or because of their absorption

problems. Down’s

syndrome patients have also been found to have low

levels of selenium

and other antioxidants.

 

In one study, refinery workers were found to have low

selenium levels

in

spite of their dietary intake of 217 micrograms per

day, which is more

than three times higher than the RDI. This study

indicates that because

of the workers’ exposure to free radicals on the job,

their bodies were

utilizing large amounts of selenium to produce the

protective enzyme

glutathione peroxidase. This suggests that exposure to

toxic

environmental chemicals increases the requirement for

this mineral.

 

The RDI for selenium is 70 micrograms for all men and

women.

 

Food Sources: There are no accurate available

measurements of the

selenium content of foods. However, it appears that

the richest sources

of selenium are seafoods, meats, and organ meats-if

the animals of

origin ate a diet high in selenium. Whole grains can

be good sources,

but, similarly, this depends on the selenium content

of the soil in

which they were grown. Fruits and vegetables generally

contain very low

amounts of selenium.

 

The refining process strips foods of much of their

selenium content. In

one study, it was found that a highly refined diet

contains 61 percent

less selenium than does a diet rich in unrefined

foods. Cooking also

reduces the content significantly, especially if the

cooking water is

discarded. Vitamin C seems to enhance the absorption

of selenium.

 

SUPPLEMENTS

 

Selenium is most often available as an individual

supplement, although

some multivitamin-mineral formulas are beginning to

include this

mineral. I recommend selenium in the form of

selenomethionine, which is

extracted from selenium-rich yeast or ocean plants.

This form is the

least toxic and appears to be the most absorbable.

 

OPTIMUM DAILY INTAKE-ODI

 

For optimum general health, the basic Optimum Daily

Intake for selenium

is:

 

 

 

100-400 mcg for men and women living in low-selenium

areas

 

(this includes coastal areas and glaciated areas)

 

50-200 mcg for men and women living in high-selenium

areas

 

 

 

The above is excerpted from the book The Real Vitamin

& Mineral Book,

by

Shari Lieberman, Ph.D and Nancy Bruning, Avery

Publishing, 1997

 

 

 

 

AIM Barleygreen

" Wisdom of the Past, Food of the Future "

 

http://www.geocities.com/mrsjoguest/Diets.html

 

 

 

 

 

 

 

 

 

 

 

 

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