What has selenium
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These studies suggest selenium is found in meat, eggs, poultry, and seafood, and is essential for antioxidant defense, thyroid function, immune regulation, and overall human health, but excessive intake can be harmful.
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The Role and Sources of Selenium in Human Health
Selenium in the Environment and Food Sources
Selenium (Se) is a trace mineral essential for human health, found in varying concentrations in soil, plants, and food. The selenium content in soil is influenced by factors such as soil type, texture, organic matter, and rainfall, which in turn affects its assimilation by plants. Fruits and vegetables generally contain low levels of selenium, while higher concentrations are found in meat, eggs, poultry, and seafood. Cereals, legumes, and their derivatives are major contributors to dietary selenium intake in many countries.
Biological Functions of Selenium
Antioxidant Defense and Thyroid Hormone Production
Selenium is a crucial component of selenoproteins, which play significant roles in antioxidant defense and thyroid hormone metabolism. Selenoproteins, such as glutathione peroxidase and thioredoxin reductase, help protect cells from oxidative damage by scavenging free radicals . Additionally, selenium is vital for the production of active thyroid hormones, which regulate metabolism and energy production.
Immune System Support
Selenium is essential for a well-functioning immune system. It enhances the activity of various immune cells, including helper T cells, cytotoxic T cells, and Natural Killer (NK) cells, thereby boosting the body's defense against infections and diseases . Adequate selenium intake has been linked to improved immune responses and reduced inflammation.
Reproductive Health and Cognitive Function
Selenium is necessary for reproductive health, influencing sperm motility and reducing the risk of miscarriage. It also supports cognitive function and may protect against cognitive decline and mental disorders .
Health Implications of Selenium Deficiency and Excess
Deficiency Risks
Selenium deficiency can lead to several health issues, including impaired immune function, cognitive decline, thyroid dysfunction, and reproductive disorders . Low selenium levels have also been associated with an increased risk of mortality and higher susceptibility to infections and chronic diseases .
Toxicity Concerns
While selenium is essential in trace amounts, excessive intake can be harmful. High selenium levels can lead to toxicity, manifesting as gastrointestinal disturbances, hair loss, and neurological damage. The narrow range between beneficial and toxic levels of selenium necessitates careful monitoring of dietary intake and supplementation .
Selenium Supplementation and Disease Prevention
Cancer and Chronic Disease Prevention
Selenium's role in cancer prevention has been widely studied, with some evidence suggesting that adequate selenium levels may reduce the risk of certain cancers, including lung, colorectal, prostate, and bladder cancers . However, the results of various studies have been inconsistent, indicating that selenium supplementation may only be beneficial in cases of deficiency.
Cardiovascular and Metabolic Health
The relationship between selenium and cardiovascular health is complex, with some studies showing benefits of higher selenium status in reducing oxidative stress and inflammation, while others have found no significant link. Similarly, selenium's impact on metabolic health, including its potential to increase the risk of type-2 diabetes at high levels, underscores the importance of balanced intake.
Conclusion
Selenium is a vital micronutrient with diverse roles in human health, from antioxidant defense and immune support to reproductive and cognitive functions. While adequate selenium intake is crucial for preventing deficiency-related health issues, excessive intake can lead to toxicity. Therefore, maintaining a balanced selenium status through diet and cautious supplementation is essential for overall health and well-being.
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