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Selenium
DESCRIPTION
Now regarded as an essential
trace Elements 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.
FUNCTIONS
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.
DEFICIENCY
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.
REQUIREMENTS
Upper safe level for daily
supplementation = 200µg
There is no EC Recommended
Daily Allowance for selenium. The average daily intake from
the diet = 65µg.
SUPPLEMENTAL USES
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).
SAFETY
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 SOURCES
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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