Overview
The
mineral selenium is found in nearly every cell in the body,
though the highest concentrations are in the kidneys, liver,
testes, pancreas and spleen. It is a potent immune system
booster, as well as the activating factor for a hormone produced
by the thyroid gland. Selenium is a known antioxidant which may
protect against cancer, heart attack, stroke, macular
degeneration, cold sores, shingles and lupus, as well as many
other diseases and effects of aging.
What
Selenium Does:
Selenium is an
antioxidant that helps protect the body by scavenging free
radicals that harm cells. It helps activate prostaglandins that
are important in regulating blood pressure and dealing with
inflammation, and is vital in the production of the enzyme,
glutathione peroxidase, which helps detoxify the body.
Where
Selenium Comes From:
The major source of
selenium is in vegetables and fruits, but the amount of selenium
in any particular fruit or vegetable is dependent on the
selenium content of the soil in which it was grown. Because of
this, people who live in areas where the soil has been depleted
of its selenium content may require more selenium than they can
reasonably consume in whole food sources.
Health
Benefits of Selenium:
In
numerous studies, including clinical trials, observation based
studies and population based studies, researchers have concluded
that people with higher intakes and blood levels of selenium
have a lower incidence of certain types of skin cancer,
colorectal cancer, prostate cancer and lung cancer.
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In studies undertaken through the 1980s and 1990s in seven
dermatology clinics in the U.S., doctors concluded that while
taking selenium supplements didn’t reduce the rate of recurrence
for skin cancer, it did decrease the occurrence of overall
cancers and death. Specifically, those who took selenium
supplements showed statistically less incidence of prostate
cancer, colorectal cancer and lung cancer.
-
The early results from two large-scale clinical trials into the
effectiveness of vitamin E and selenium against cancer suggest
that a combination of the two nutrients in supplement form may
be effective in preventing cancer and heart disease.
According to the National Institutes of Health, “Selenium is one
of a group of antioxidants that may help limit the oxidation of
LDL and thereby help to prevent coronary artery disease. A major
study underway in France is investigating how effective selenium
is alone and taken with vitamin E in preventing coronary
disease.
Because
people with rheumatoid arthritis have low blood levels of
selenium and reduced selenium intake, the National Institutes of
Health postulates that selenium may help control symptoms of
rheumatoid arthritis by controlling the levels of free radicals
in the blood.
Because
HIV/AIDS often results in malabsorption of some nutrients, it’s
not unusual for those who are HIV positive to have low levels of
selenium in their blood. Doctors frequently prescribe selenium
supplements to combat the depletion and malabsorption that is
associated with HIV/AIDS. In at least two separate studies, low
levels of selenium were linked with faster disease progression
and higher rate of death among AIDS patients. The role that
selenium plays in the immune system may be the reason, as
researchers believe that low levels of selenium compromise the
immune system.
In
addition to the major studies noted above, there have been a
number of smaller studies that indicate that selenium may have a
significant effect on the progression of macular degeneration,
skin disorders including acne and rosacea, asthma, lupus,
pancreatitis and diabetes.
Recommended Daily Intake of Selenium:
The
Institutes of Medicine has established a Recommended Dietary
Intake for selenium. The RDA is the average daily intake that
the Institutes of Medicine believe is sufficient for the
nutrition needs of approximately 97% of the population.
-
Children 1-3 years – 20 mcg
-
Children 4-8 years – 30 mcg
-
Children 9-13 years – 40 mcg
-
Males 14-18 – 55 mcg
-
Females 14-18 – 55 mcg
-
Males 19+ - 55 mcg
-
Females 19+ - 55 mcg
-
Males 50+ - 55 mcg
-
Females 50+ - 55 mcg
-
Pregnant females – 60 mcg
-
Lactating females – 70 mcg
The
Institute of Medicine has also established upper tolerable
intake levels for selenium. Those levels are established for
supplements that carry a risk of toxicity at high levels. While
selenium toxicity is rare, there is a condition called selenosis
that results from excessive levels of selenium in the blood. The
established upper levels for selenium are:
-
Children 1-3 y – 90 mcg
-
Children 4- 8 - 150 mcg
-
Children 9-13 – 280 mcg
-
Males 14-18 – 400 mcg
-
Females 14-18 – 400 mcg
-
Males 19+ - 400 mcg
-
Females 19+ - 400 mcg
Symptoms of Selenium Deficiency:
While
selenium deficiency is rare in the United States, certain
conditions may make it more difficult for the body to absorb
selenium. In addition, people in areas where the soil is
depleted of selenium may be at risk of selenium deficiency. The
symptoms of selenium deficiency include hypothyroidism, a
weakened immune system and a form of heart disease. In addition,
according to a 2003 study published in the Journal of Nutrition,
scientists believe that a selenium deficiency can make the body
more susceptible to illnesses caused by other deficiencies or
biological stress.
Selenium
Toxicity:
High
levels of selenium in the blood can cause a condition known as
selenosis, which causes gastrointestinal upsets, hair loss,
white/blotchy nails, fatigue, irritability, garlicky breath and
mild nerve damage. The few reported cases of selenium toxicity
in the United States have resulted from industrial accidents and
manufacturing errors that resulted in unnaturally high doses of
selenium in a supplement. The National Institutes of Medicine
has established an upper tolerable intake level of selenium of
450 mcgs per day for adults.
Supplementing with Selenium:
The FDA
has stated that most people in the United States can get an
adequate amount of selenium through diet; however, selenium
levels in food are depended on the selenium in the soil in which
the food was grown. In addition, selenium is destroyed when
foods are destroyed or processed, which may make selenium less
available than is believed. Because a number of chronic
diseases, including Crohn’s disease, HIV/AIDS, diabetes, asthma
and arthritis have been associated with low levels of selenium,
a daily supplement that contains selenium may help boost the
immune system and provide necessary antioxidants to help slow
and/or prevent conditions commonly associated with aging.
Selenium
is one of 11 essential minerals and over 70 important nutrients
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