Selenium
DESCRIPTION:
Now regarded as an essential trace
element in humans and animals, selenium is found in uneven
quantities in parts of the earth’s surface. Selenium toxicity
has been noted in areas where selenium content of the ground is
high, but selenium deficiency is a far more widespread problem -
contributing to Infertility, heart problems, eye disease
and premature Aging.
Selenium carries out its main
functions as part of the enzyme glutathione peroxidase.
Glutathione peroxidase is an antioxidant that protects
intracellular structures against oxidative damage by free
radicals.
Selenium is known to have a role in
the following:
- Preservation of normal liver
function.
- Antioxidant protection of all
body cells.
- Maintenance of a healthy
heart.
- Inhibition of harmful effects
from heavy metals such as arsenic, cadmium, mercury and
lead.
- Production of beneficial
anti-inflammatory prostaglandins.
- Production of thyroxine
hormone.
Selenium deficiency has
traditionally occurred in areas where the soil is particularly
low in this mineral. However, as modern lifestyles have allowed
us to eat foods from very many different countries of origin,
true selenium deficiency has become less of a problem.
One selenium deficiency disease is
known as Keshan’s disease - after the province in China that
has the lowest soil selenium levels in the world. Symptoms are
mainly to do with the heart - specifically involving wastage of
the heart muscle.
Another selenium deficiency disease
is known as Kaschin-Beck disease, and affects the cartilage in
the joints.
Upper safe level for daily
supplementation = 200µg
There is no EC Recommended Daily
Allowance for selenium. The average daily intake from the diet =
65µg.
The groups of people particularly
found to be at risk of selenium deficiency are as follows:
- Vegetarians (1).
- The elderly (2).
- Pregnant and nursing mothers
(3).
- Smokers (4).
Any of the above groups may benefit
from additional selenium in the form of supplement, although
efforts should also be taken to improve the diet as well.
Rheumatoid Arthritis:
A study carried out in a New Zealand clinic found that only 6%
of the patients with rheumatoid Arthritis (RA) achieved their
recommended daily intake for selenium. The study concluded there
was a need for selenium supplementation for those with RA (5).
Evidence of disturbed selenium
regulation occurs at intakes above 750µg and deterioration and
loss of nails have been noted in adults ingesting 900µg per
day.
INTERACTIONS
AND CONTRA-INDICATIONS
There are no known drug interactions
or contra-indications for selenium.
Vitamin
E is a very important synergistic factor that enhances the
benefits of selenium and vice versa.
Food (mg/100g)
Organ meats approx.40
Fish and shellfish approx.32
Meat approx.18
Wholegrains & cereals approx.12
Dairy products approx.5
Fruit and vegetables approx.2
Selenium is especially variable in
plant foods, dairy products and eggs because of the tremendous
variation in selenium content of the soil.
REFERENCES:
1. Kadrabová J. Selenium status,
plasma zinc, copper, and magnesium in vegetarians. Biol Trace
Elem Res, 50;1:13-24, 1995.
2. Olivieri O et al. Low selenium status in the elderly
influences thyroid hormones. Clin Sci (Cholch), 89;6:637-642,
1995.
3. Sanz Alaejos M and Diaz Romero C. Selenium in human
lactation. Nutr Rev, 53;6:159-166, 1995.
4. Zachara BA et al. Decreased selenium concentration and
glutathione peroxidase activity in blood and increase of these
parameters in malignant tissue of lung cancer patients. Lung,
175;5:321-332, 1997.
5. Stone J et al. Inadequate Calcium, Folic Acid, Vitamin E,
Zinc, and selenium intake in rheumatoid arthritis patients:
results of a dietary survey. Semin Arthritis Rheum,
27;3:180-185, 1997.
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