"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. 

What is the health risk of too much Selenium?

High blood levels of selenium (greater than 100 μg/dL) can result in a condition called selenosis.
Symptoms of selenosis include gastrointestinal upsets, hair loss, white blotchy nails, garlic breath odor, fatigue, irritability, and mild nerve damage.

Selenium toxicity is rare in the U.S. The few reported cases have been associated with industrial accidents and a manufacturing error that led to an excessively high dose of selenium in a supplement.
The Institute of Medicine of the National Academy of Sciences has set a tolerable upper intake level (UL) for selenium at 400 micrograms per day for adults to prevent the risk of developing selenosis.

Tolerable Upper Intake Levels for Selenium for Infants, Children, and Adults

Age	Males and Females (μg/day)
0 - 6 months	45
7 - 12 months	60
1-3 y	90
4-8 y	150
9-13 y	280
14-18 y	400
19 y +	400

 

When can Selenium deficiency occur?

Human selenium deficiency is rare in the U.S. but is seen in other countries, most notably China, where soil concentration of selenium is low. There is evidence that selenium deficiency may contribute to development of a form of heart disease, hypothyroidism, and a weakened immune system. There is also evidence that selenium deficiency does not usually cause illness by itself. Rather, it can make the body more susceptible to illnesses caused by other nutritional, biochemical or infectious stresses.

Three specific diseases have been associated with selenium deficiency:

Keshan Disease, which results in an enlarged heart and poor heart function, occurs in selenium deficient children.

Kashin-Beck Disease, which results in osteoarthropathy involving degeneration, necrosis of the joints and of epiphyseal-plate cartilages of the legs and arms. 

Myxedematous Endemic Cretinism, which results in mental retardation

Keshan disease was first described in the early 1930s in China, and is still seen in large areas of the Chinese countryside with selenium poor soil. Dietary intake in these areas is less than 19 micrograms per day for men and less than 13 micrograms per day for women, significantly lower than the current RDA for selenium. Researchers believe that selenium deficient people infected with a Coxsackie virus are most likely to develop Keshan disease.

Selenium deficiency has also been seen in people who rely on total parenteral nutrition (TPN) as their sole source of nutrition.

Major symptoms of deficiency included poor growth, muscle pain and weakness, loss of pigmentation of hair and skin, and whitening of nail beds. Poor growth may be associated with the role of selenium in thyroid hormone metabolism.

What is the recommended dietary intake for Selenium?

Recommendations for selenium are provided in the Dietary Reference Intakes developed by the Institute of Medicine. The RDA recommends the average daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (97-98%) healthy individuals in each age and gender group.

Recommended Dietary Allowances (RDA) for Selenium for Children and Adults 

Age (years)	Males and Females (μg/day)	Pregnancy (μg/day)	Lactation (μg/day)
1-3 y	20	N/A	N/A
4-8 y	30	N/A	N/A
9-13 y	40	N/A	N/A
14-18 y	55	60	70
19 y +	55	60	70

There is insufficient information on selenium to establish a RDA for infants. An Adequate Intake (AI) has been established that is based on the amount of selenium consumed by healthy infants who are fed breast milk.

Adequate Intake for Selenium for Infants

Age (months)	Males and Females (μg/day)
0-6 months	15
7-12 months	20

What foods provide Selenium?

Plant foods are the major dietary sources of selenium in most countries throughout the world. The content of selenium in food depends on the selenium content of the soil where plants are grown or animals are raised.
For example, researchers know that soils in the high plains of northern Nebraska and the Dakotas have very high levels of selenium. People living in those regions generally have the highest selenium intakes in the United States. In the U.S., food distribution patterns across the country help prevent people living in low-selenium geographic areas from having low dietary selenium intakes.

Selenium also can be found in some meats and seafood. Animals that eat grains or plants that were grown in selenium-rich soil have higher levels of selenium in their muscle. In the U.S., meats and bread are common sources of dietary selenium. Some nuts are also sources of selenium.

*DV = Daily Value. DVs are reference numbers developed by the Food and Drug Administration (FDA) to help consumers determine if a food contains a lot or a little of a specific nutrient. The DV for selenium is 70 micrograms (ug).
 

Food	Micrograms (μg)	Percent DV*
Brazil nuts, dried, unblanched, 1 ounce	544	780
Tuna, light, canned in oil, drained, 3 ounces	63	95
Beef, cooked, 3½ ounces	35	50
Spaghetti w/ meat sauce, frozen entrée, 1 serving	34	50
Cod, cooked, 3 ounces	32	45
Turkey, light meat, roasted, 3½ ounces	32	45
Beef chuck roast, lean only, roasted, 3 ounces	23	35
Chicken Breast, meat only, roasted, 3½ ounces	20	30
Noodles, enriched, boiled, 1/2 cup	17	25
Macaroni, elbow, enriched, boiled, 1/2 cup	15	20
Egg, whole, 1 medium	14	20
Cottage cheese, low fat 2%, 1/2 cup	12	15
Oatmeal, instant, fortified, cooked, 1 cup	12	15
Rice, white, enriched, long grain, cooked, 1/2 cup	12	15
Rice, brown, long-grained, cooked, 1/2 cup	10	15
Bread, whole wheat, commercially prepared, 1 slice	10	15
Walnuts, black, dried, 1 ounce	5	8
Bread, white, commercially prepared, 1 slice	4	6
Cheddar cheese, 1 ounce	4	6

"Selenium = Sulfur": Do you know what this mean???

The chemistry of selenium is similar to that od sulfur; consequently, selenium can often subsitute for sulfur.
The total body selenium contenet ranges from about 13 to 30mg.

       * 34Se                         " Structure of trigonal Selenium" 
                                                                
                                     
                                     
                                       +NH3
                                           :
"Selenomethionine"      HC--CH2--CH2--Se--CH3
                                           :
                                        COO-


                                      +NH3 
                                          :
"Selenocysteine"          HC--CH2--Se--H
                                          :
                                       COO-

Do you know what Selenium is.

Selenium, a nonmetal, is a trace mineral that is essential to good health but required only in small amounts. Selenium is incorporated into proteins to make selenoproteins, which are important antioxidant enzymes. The antioxidant properties of selenoproteins help prevent cellular damage from free radicals. Free radicals are natural by-products of oxygen metabolism that may contribute to the development of chronic diseases such as cancer and heart disease. Other selenoproteins help regulate thyroid function and play a role in the immune system.