Diff: Selenium
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'''Selenium''' is a trace element that is crucial for various physiological functions in the human body. It serves as an essential component of selenoproteins, which have antioxidant properties and play roles in DNA synthesis, immune function, and thyroid hormone metabolism. While selenium is necessary for health, excessive intake can be harmful. It is obtained through dietary sources, and its optimal levels are vital for overall well-being. |
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==Overview== |
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Trace Element: |
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Essential Nutrient: Selenium is an essential trace element required for the proper functioning of the human body. |
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Selenoproteins: It is a key component of selenoproteins, a family of proteins containing selenium in the form of the amino acid selenocysteine. |
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Antioxidant Properties: |
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Cellular Defence: Selenium's antioxidant properties help protect cells from oxidative stress. |
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==Functions of Selenium== |
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Antioxidant Defence: |
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Selenoproteins: Selenium is a component of various selenoproteins, including glutathione peroxidases, which neutralize reactive oxygen species. |
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Thyroid Hormone Metabolism: |
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Conversion of T4 to T3: Selenium is involved in the conversion of thyroxine (T4) to triiodothyronine (T3), active thyroid hormones. |
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DNA Synthesis and Repair: |
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Genomic Stability: Selenium plays a role in DNA synthesis and repair, contributing to genomic stability. |
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Immune Function: |
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Immune Response: Selenium is important for the proper functioning of the immune system. |
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Male Reproductive Health: |
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Spermatogenesis: Selenium is involved in male reproductive health, specifically in spermatogenesis. |
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==Dietary Sources of Selenium== |
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Seafood: |
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Fish: Tuna, halibut, sardines, and shrimp. |
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Shellfish: Oysters, crab, and mussels. |
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'''Selenium''' is an essential trace mineral. The body uses it to make selenoproteins, a group of proteins involved in antioxidant defence, thyroid hormone metabolism, immune function, reproduction, and DNA-related processes. |
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Meat and Poultry: |
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Selenium is needed only in small amounts. Both too little and too much can cause health problems, so it is not a nutrient where more is automatically better. |
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Beef, Pork, Chicken: Meat and poultry are good sources of selenium. |
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== Biological Role == |
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Selenium is incorporated into proteins as the amino acid selenocysteine. Important selenoproteins include glutathione peroxidases, thioredoxin reductases, and iodothyronine deiodinases. |
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Brazil Nuts: |
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These proteins help: |
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High Selenium Content: Brazil nuts are particularly rich in selenium, but consumption should be moderate due to the risk of excessive intake. |
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* Limit oxidative damage. |
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* Support thyroid hormone activation and metabolism. |
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* Support immune and reproductive function. |
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* Take part in normal cellular maintenance. |
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Eggs: |
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Selenium and iodine are linked through thyroid biology, but selenium supplements do not replace diagnosis or treatment of thyroid disease. |
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Selenium-Rich Eggs: Eggs, especially those from chickens fed selenium-rich diets. |
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== Food Sources == |
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Food selenium content depends partly on soil selenium levels. Sources include: |
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Grains and Seeds: |
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* Brazil nuts. |
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* Fish and shellfish. |
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* Meat and poultry. |
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* Eggs. |
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* Some cereals and grains. |
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Brown Rice, Sunflower Seeds: Some grains and seeds contain selenium. |
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==Recommended Daily Intake== |
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Varied Requirements: The recommended daily intake varies by age, sex, and life stage. For adults, it is generally around 55 micrograms. |
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==Deficiency and Excess== |
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Deficiency Symptoms: |
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Brazil nuts can be very high in selenium, so frequent large servings can push intake too high. |
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Keshan Disease: Severe selenium deficiency may contribute to Keshan disease, a form of cardiomyopathy. |
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== Intake == |
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UK NHS guidance gives adult daily requirements of 75 mcg for men and 60 mcg for women aged 19 to 64. NIH guidance in the United States gives a recommended adult amount of 55 mcg a day, with higher amounts during pregnancy and breastfeeding. |
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Excess Intake: |
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These figures come from different national reference systems, but both show that selenium is required in microgram amounts, not milligram amounts. |
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Selenosis: Excessive selenium intake, usually from supplements, can lead to selenosis, characterized by symptoms such as hair and nail loss, gastrointestinal issues, and neurological problems. |
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==Interactions and Considerations== |
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Interactions with Other Nutrients: |
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== Deficiency and Excess == |
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Selenium deficiency is uncommon in people with varied diets in many high-income countries, but it can occur where soil selenium is low or where medical conditions affect intake or absorption. |
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Iodine: Adequate selenium levels are important for optimal thyroid function in the presence of iodine. |
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Severe deficiency has been linked with Keshan disease, a cardiomyopathy described in low-selenium regions, and with impaired immune or thyroid-related function. |
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Medical Conditions: |
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Excess selenium can cause selenosis. Features may include garlic-like breath, metallic taste, nausea, diarrhoea, brittle hair or nails, hair loss, skin rash, fatigue, irritability, and nerve symptoms. Excess usually comes from high-dose supplements or very high selenium foods taken in large amounts. |
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Thyroid Disorders: Individuals with thyroid disorders may have specific considerations regarding selenium intake. |
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==Research and Health Benefits== |
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Cancer Prevention: |
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== Research == |
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Selenium has been studied for cancer, cardiovascular disease, thyroid disease, fertility, and immune function. The evidence is mixed and depends on baseline selenium status, dose, chemical form, and population. Routine high-dose supplementation is not supported for the general population. |
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Anticancer Properties: Some studies explore the potential link between adequate selenium levels and a reduced risk of certain cancers. |
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== See Also == |
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* [[Vitamin_K]] |
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* [[Choline]] |
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* [[Common_Medical_Terms]] |
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Cardiovascular Health: |
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== References == |
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* [https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/ NIH Office of Dietary Supplements: Selenium health professional fact sheet] |
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* [https://ods.od.nih.gov/factsheets/Selenium-Consumer/ NIH Office of Dietary Supplements: Selenium consumer fact sheet] |
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* [https://www.nhs.uk/conditions/vitamins-and-minerals/others/ NHS: Selenium] |
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* [https://ods.od.nih.gov/factsheets/list-all/ NIH Office of Dietary Supplements: Dietary supplement fact sheets] |
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Heart Disease Prevention: Research suggests that optimal selenium levels may contribute to cardiovascular health. |
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[[Category:Nutrition]] |
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[[Category:Medicine]] |