"Quiz"- You can test yourself.

1. What is Selenium?

2. Where does Selenium get absorbed in the body?

3. What are the major dietary sources of Selenium?

4. Give one symptom & disease of Selenium deficiency?

5. How much is a tolerable upper intake level for adults?

6. Is there any one need a Selenium supplementation? 

What is Selenium?

It is non-metal ultratrace element. It is found in body in small quantity. The amounts are typically measured in micrograms (mcg). It functions through an association with protein, known as selenoproteins. It acts as antioxidant to scavenge free radicals to protect tissues from oxidation.

Selenium and Cancer

Scientists are now revealing the anti-oxidant characteristics of Selenium to protect the cell from oxidative damages.
A new article just released on May 19, 2011 with an evidence to show the potential benefit of Selenium in reducing Lipid Hydro-peroxide - a molecule in low density lipoprotein (LDL). LDL is responsible for Coronary Heart Disease.
The research has been done on 10 overweight and 10 normal-weight healthy subjects. The subjects were supplemented with 200 µg sodium selenite/day for 3 weeks with a 3-week placebo control and inversion of treatment periods. Result shows no significant effect in normal-weight and control subjects, however the lipid hydro-peroxide was significantly reduced in overweight subjects. 




Savory LA, Kerr CJ, Whiting P, Finer N, McEneny J, Ashton T. (2011). 

Selenium Supplementation and Exercise: Effect on Oxidant Stress in Overweight Adults. Obesity. 11

Maternal selenium status during early gestation and risk for preterm birth

Preterm birth occurs in 5%-13% of pregnancies. it is a leading cause of perinatal mortality and morbidity and has adverse long-term consequences for the health of the child. because of the role selenium plays in attenuating inflammation, and because low concentrations of selenium have been found in women with preeclampsia. Low maternal selenium status during early gestation would increase the risk of preterm birth.

Study has shown 60 women (5.3%) among (n = 1197) who had preterm bith, 21 had premature rupture of the membranes and 13 had preeclampsia. The serum selenium concentration at 12 weeks' gestation was significantly lower among women who had  apreterm birth than among those who delivered at term.
Women in the lowest quartile of serum selenium had twice the risk of preterm birth as women in the upper three quartiles, even after adjustment for the occurence of preeclampsia.

Having low serum selenium at the end of the first trimester was related to preterm birth and was independent of the mother having preeclampsia. Low maternal selenium status during early gestation may increase the risk of preterm premature rupture of the membranes, which is a major cause of preterm birth.

From Canadian Medical Association Journal, March 22, 2011, 183(5), 549-555.

Do we need to take Supplemental Selenium?

Healthy individuals don't need to take supplemental selenium, but  most cases of selenium depletion or deficiency are associated with severe gastrointestinal problems, such as Crohn's disease, or with surgical removal of part of the stomach. These and other gastrointestinal disorders can impair selenium absorption.

People with acute severe illness who develop inflammation and widespread infection often have decreased levels of selenium in their blood.

People with iodine deficiency may also benefit from selenium supplementation.

Supplemental Selenium

Selenium occurs in staple foods such as corn, wheat, and soybean as selenomethionine, the organic selenium analogue of the amino acid methionine. Selenomethionine can be incorporated into body proteins in place of methionine, and serves as a vehicle for selenium storage in organs and tissues. Selenium supplements may also contain sodium selenite and sodium selenate, two inorganic forms of selenium. Selenomethionine is generally considered to be the best absorbed and utilized form of selenium.

Do you know what Selenophosphate Synthetase (SPS) is

Selenophosphate Synthetase (SPS)

At least two forms of selenophosphate synthetase have been identified in the body.
One form (called SPS1) does not contain selenocysteine and is thought to recycle selenuim from selenocysteine.
The SPS2 isoform, which contains selenocysteine, catalyzes thr synthesis of selenophosphate from selenide, as shown here:

                                  Selenophosphate synthetase
              H2Se-------------------------------------------------> HSePO2-3

             Selenide        ATP---------------> AMP + Pi     Selenophosphate

Selenophosphate is a key compound needed in the body to synthesize other selenocysteine-containing proteins or enzymes such as glutathione peroxidase, deiodinase, thioredoxin reductase, selenoprotein P, and others.

How does Selenium digest,absorb and store in the body?

Absorption
Selenium, in organic and inorganic forms, is efficiently absorbed. The duodenum appears to be the primary absorptive site, with some absorption also occuring in the jejunum and ileum.
Selenoamino acid absorption, which occurs through amino acid transport systems, is estimated to be over 80%. Selenomethionine is thought to be better absorbed than selenocysteine.

Factors Influencing Selenium Absorption
Vitamin C, A, and E, as well as the presence of reduced glutathione in the intestinal lumen.
Heavy metals (such as mercury) and phytates are thought to inhibit selenium absorption through chelation and precipitation.

Uptake& Storage
The mechanism by which selenium is freed from plasma transport proteins and taken up by tissue is not known. The uptake of selenium by one of the main selenium-containing metalloenzymes, glutathione peroxidase.
That is, ingesting selenium in inorganic forms, such as selenite, cause more of the mineral to be incorporated into glutathione peroxidase than ingesting the organic form, selenomethionine, does.