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.