Selenium: Difference between revisions

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Selenium

Selenium is a trace element that is essential for human health. It is a component of several major metabolic pathways, including thyroid hormone metabolism, antioxidant defense systems, and immune function. Selenium is incorporated into proteins to make selenoproteins, which are important antioxidant enzymes.

Biological Role

Selenium plays a critical role in the body by contributing to the antioxidant defense system, which protects cells from damage caused by free radicals. It is also essential for the proper functioning of the thyroid gland, as it is involved in the conversion of thyroxine (T4) to triiodothyronine (T3), the active form of thyroid hormone.

Antioxidant Function

Selenium is a key component of the enzyme glutathione peroxidase, which helps to reduce oxidative stress by neutralizing harmful peroxides. This function is crucial in protecting cells from oxidative damage, which can lead to chronic diseases such as cancer and cardiovascular disease.

Thyroid Function

The thyroid gland contains more selenium per gram of tissue than any other organ in the body. Selenium-dependent enzymes, such as iodothyronine deiodinases, are responsible for the activation and deactivation of thyroid hormones. Adequate selenium levels are necessary to maintain optimal thyroid function and metabolism.

Immune System

Selenium is important for the immune system, as it enhances the proliferation of activated T-cells and the production of antibodies. It also plays a role in the regulation of inflammation and the prevention of infections.

Dietary Sources

Selenium is found in a variety of foods. The amount of selenium in plant-based foods depends on the selenium content of the soil in which they are grown. Animal-based foods generally have more consistent selenium levels.

Rich Sources

- Brazil nuts - Seafood (e.g., tuna, halibut, sardines) - Meat (e.g., beef, chicken, turkey) - Eggs - Dairy products

Deficiency

Selenium deficiency can lead to several health problems, including Keshan disease, a type of cardiomyopathy, and Kashin-Beck disease, a type of osteoarthropathy. Symptoms of selenium deficiency may include muscle weakness, fatigue, and mental fog.

Toxicity

While selenium is essential for health, excessive intake can lead to selenium toxicity, known as selenosis. Symptoms of selenosis include gastrointestinal disturbances, hair loss, white blotchy nails, and mild nerve damage.

Recommended Intake

The recommended dietary allowance (RDA) for selenium varies by age, sex, and life stage. For adults, the RDA is 55 micrograms per day. Pregnant and lactating women have higher requirements.

Nutrition information of Selenium

USDA on Selenium

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+Selenium
-[[File:Selen 1.jpg|thumb|Selen_1]]
+Selenium is a trace element that is essential for human health. It is a component of several major metabolic pathways, including thyroid hormone metabolism, antioxidant defense systems, and immune function. Selenium is incorporated into proteins to make selenoproteins, which are important antioxidant enzymes.
-{{Infobox element
+==Biological Role==
-| name = Selenium
+Selenium plays a critical role in the body by contributing to the antioxidant defense system, which protects cells from damage caused by free radicals. It is also essential for the proper functioning of the [[thyroid gland]], as it is involved in the conversion of [[thyroxine]] (T4) to [[triiodothyronine]] (T3), the active form of thyroid hormone.
-| image name = Selen 1.jpg
-| alt = A photo of a selenium crystal.
-| caption = Selenium crystal
-| pronunciation = {{IPA|/səˈliːniəm/}}
-| element category = Nonmetal
-| symbol = Se
-| atomic number = 34
-| appearance = Black, red, and gray (not pictured) allotropes
-| standard atomic weight = 78.96(3)
-| electron configuration = [Ar] 3d10 4s2 4p4
-| per shell =
-st: 2
-nd: 8
-rd: 18
-th: 6
-| physical properties = yes
-| phase = solid
-| sublimation point = 958 K (685 °C, 1265 °F)
-| boiling point = 958 K (685 °C, 1265 °F)
-| density near rt = 4.81 g/cm3
-| when liquid, at m.p. = 4.39 g/cm3
-| triple point = 494 K, 101 kPa
-| heat of fusion = 6.69 kJ/mol
-| heat of vaporization = 95.48 kJ/mol
-| molar heat capacity = 25.363 J/(mol·K)
-| vapor pressure = P (Pa) 1 10 100 1 k 10 k 100 k
-at T (K) 496 547 616 712 853 1057
-| atomic properties = yes
-| oxidation states = 6, 5, 4, 3, 2, 1, −1, −2 (an amphoteric oxide)
-| electronegativity = 2.55
-| ionization energies =
-| 1st: 941.0 kJ/mol
-| 2nd: 2045 kJ/mol
-| 3rd: 2973.7 kJ/mol
-| covalent radius = 120±4 pm
-| van der Waals radius = 190 pm
-| spectral lines of selenium
-| other properties = yes
-| natural occurrence = primordial
-| crystal structure = {{nowrap|[[Hexagonal crystal family|Hexagonal]]}} close-packed (hcp)
-| magnetic ordering = diamagnetic
-| CAS Number = 7782-49-2
-| history =
-| named by = Jöns Jakob Berzelius
-| discovery = Jöns Jakob Berzelius and Johan Gottlieb Gahn (1817)
-}}
-Selenium is an element needed by the [[body]] only in very small amounts that helps maintain [[tissue]] elasticity.
+===Antioxidant Function===
+Selenium is a key component of the enzyme [[glutathione peroxidase]], which helps to reduce oxidative stress by neutralizing harmful peroxides. This function is crucial in protecting cells from oxidative damage, which can lead to chronic diseases such as [[cancer]] and [[cardiovascular disease]].
-{{intro}}
+===Thyroid Function===
-Selenium is present in biologic systems in amino acids, such as selenocysteine and selenomethionine, usually as a part of proteins, which are referred to as selenoproteins.  While selenium is present in many important enzyme systems, deficiency of selenium is rare.
+The thyroid gland contains more selenium per gram of tissue than any other organ in the body. Selenium-dependent enzymes, such as iodothyronine deiodinases, are responsible for the activation and deactivation of thyroid hormones. Adequate selenium levels are necessary to maintain optimal thyroid function and metabolism.
-'''Selenium''' is a nonmetal chemical element with the symbol Se and atomic number 34. It is a rare element, found in the Earth's crust at an average concentration of just 0.05 parts per million. Selenium is a member of the chalcogen group on the periodic table, along with sulfur and tellurium.
-==History==
+===Immune System===
-Selenium was discovered in 1817 by Jöns Jakob Berzelius and Johan Gottlieb Gahn. It was named after the Greek word "σελήνη" (selene), which means "moon", because of its similarity to tellurium, which had been named after the Latin word "tellus", meaning "earth".
+Selenium is important for the immune system, as it enhances the proliferation of activated T-cells and the production of antibodies. It also plays a role in the regulation of inflammation and the prevention of infections.
-==Occurrence==
+==Dietary Sources==
+Selenium is found in a variety of foods. The amount of selenium in plant-based foods depends on the selenium content of the soil in which they are grown. Animal-based foods generally have more consistent selenium levels.
-[[File:Selenium pathways and transformations.png|Selenium_pathways_and_transformations]]
+===Rich Sources===
+- [[Brazil nuts]]
+- [[Seafood]] (e.g., tuna, halibut, sardines)
+- [[Meat]] (e.g., beef, chicken, turkey)
+- [[Eggs]]
+- [[Dairy products]]
-Selenium is a relatively rare element, found in the Earth's crust at an average concentration of just 0.05 parts per million. It is found in a number of minerals, including the sulfides pyrite and galena, and the selenides naumannite and clausthalite.
+==Deficiency==
+Selenium deficiency can lead to several health problems, including [[Keshan disease]], a type of cardiomyopathy, and [[Kashin-Beck disease]], a type of osteoarthropathy. Symptoms of selenium deficiency may include muscle weakness, fatigue, and mental fog.
-Selenium is also present in someplants, particularly in those grown in soil with high selenium content. It is an essential trace element for many organisms, including humans, but can be toxic in large amounts.
+==Toxicity==
+While selenium is essential for health, excessive intake can lead to selenium toxicity, known as selenosis. Symptoms of selenosis include gastrointestinal disturbances, hair loss, white blotchy nails, and mild nerve damage.
-==Properties==
+==Recommended Intake==
-Selenium has several allotropes, including black, red, and gray forms. It is a nonmetal with properties that are intermediate between those of metals and nonmetals. It is a semiconductor, meaning it can conduct electricity under certain conditions, and has a wide range of uses in electronics and other industries.
+The recommended dietary allowance (RDA) for selenium varies by age, sex, and life stage. For adults, the RDA is 55 micrograms per day. Pregnant and lactating women have higher requirements.
-Selenium is also important for the human body, as it is a necessary nutrient in small amounts. It is involved in the production of thyroid hormones and has antioxidant properties. However, like many trace elements, it can be toxic in large amounts.
+==See Also==
+* [[Trace elements]]
+* [[Antioxidants]]
+* [[Thyroid hormone]]
+* [[Immune system]]
-==Uses==
+{{Trace elements}}
-Selenium has a variety of uses in industry and technology. It is a key ingredient in many types of glass, including glass used in the production of photovoltaic cells. It is also used in the production of semiconductors, including the production of certain types of solar cells.
+{{Nutrition}}
-In addition, selenium has uses in the metallurgical industry, as a component of stainless steel and other alloys. It is also used in the production of pigments and as a catalyst in chemical reactions.
+[[Category:Trace elements]]
+[[Category:Nutrition]]
-Selenium is also important for the human body, and is used in some dietary supplements. However, it can be toxic in large amounts and should be consumed only in the recommended amounts.
+[[Category:Antioxidants]]
+[[Category:Thyroid]]
-{{def}}
-[[Keshan disease]], an endemic cardiomyopathy affecting children and young women in parts of China, has been linked to selenium deficiency, although other nutritional deficiencies or local factors may also may a role.
-{{toxicity}}
-Excess selenium exposure can cause cirrhosis in laboratory animals, but toxicity in humans has been linked largely to skin, hair and nail changes.  An outbreak of possible selenium toxicity due to a nutritional supplement was marked by nausea, diarrhea, irritability, fatigue, neuropathy, hair loss and nail changes, without liver test abnormalities.
-{{trace elements}}
-{{stubd}}
-==References==
-{{Reflist}}
-==External links==
-{{Commons|Selenium}}
-{{Periodic table}}
-[[Category:Chemical elements]]
-[[Category:Nonmetals]]
-[[Category:Chalcogens]]

Aluminum	Copper	Nickel
Antimony	Fluorine	Rubidium
Barium	Iodine	Selenium
Boron	Lead	Silver
Bromine	Lithium	Strontium
Cadmium	Manganese	Tin
Chromium	Mercury	Vanadium
Cobalt	Molybdenum	Zinc