Selenium is a trace element that plays crucial roles in human health, functioning as a component of various proteins and enzymes essential for the body's systems and processes.

It is particularly vital for thyroid function, where it facilitates the synthesis and metabolism of thyroid hormones.

These hormones, thyroxine (T4) and triiodothyronine (T3), are pivotal for regulating metabolism, growth, and development throughout the body.

Beyond thyroid support, selenium's primary role lies in its participation in antioxidant defense mechanisms.

It is a key component of glutathione peroxidase, an enzyme that protects cells from oxidative damage caused by free radicals.

Free radicals are unstable molecules that can interact with and damage cellular structures, contributing to aging and various diseases.

It also plays a critical role in DNA synthesis and repair, essential processes for maintaining genetic integrity and regulating cellular functions.

Moreover, this nutrient is involved in modulating gene expression, influencing how genetic information is utilized by cells for growth, repair, and overall function.

Benefits of Selenium

This nutrient offers a range of potential health benefits, making it a valuable nutrient to include in your diet or as a supplement.

One significant area of interest is its potential role in cancer prevention.

Research suggests that it may have protective effects against certain types of cancer, including prostate, breast, and colorectal cancers.

These effects are thought to be linked to selenium's antioxidant properties and its ability to support immune function, which helps the body recognize and destroy cancerous cells.

In addition to cancer prevention, it may contribute to cardiovascular health by reducing the risk of heart disease.

Studies have indicated that selenium's antioxidant and anti-inflammatory effects may help protect blood vessels and reduce oxidative stress, which is a contributing factor to cardiovascular disease.

Selenium's impact on cognitive function is another emerging area of research.

Preliminary studies suggest that this nutrient may play a role in maintaining cognitive health and reducing the risk of cognitive decline associated with aging.

Further research is needed to fully understand these potential benefits and their mechanisms.

Furthermore, this nutrient supports immune function by enhancing the activity of immune cells and aiding in the defense against infections. 

It may also possess antiviral properties, potentially reducing the severity and duration of viral illnesses such as the common cold.

Dietary Sources of Selenium

Including selenium-rich foods in your diet is an effective way to ensure adequate intake of this essential nutrient.

Brazil nuts are among the best dietary sources of selenium, providing a significant portion of the recommended daily intake with just a few nuts.

This high content is attributed to the selenium-rich soil in which Brazil nuts are grown.

Additionally, Brazil nuts are rich in fiber, protein, and healthy fats, making them a nutritious choice.

Fatty fish, such as salmon, sardines, and mackerel, are also excellent sources.

Seafood in general, including shellfish like shrimp and lobster, provides significant amounts of it.

Poultry such as chicken and turkey, as well as meats like beef and pork, contribute to selenium intake.

Whole grains, including brown rice and oats, are valuable sources of selenium in the diet.

Eggs, dairy products, and certain fruits and vegetables also contain selenium, albeit in smaller amounts.

Specific mushrooms like shiitake and maitake are known for their selenium content and can be incorporated into various dishes.

Supplementation and Considerations

Selenium supplements are available in various forms, including tablets, capsules, and liquids, offering a convenient option to boost selenium intake when dietary sources are insufficient.

However, it's essential to approach supplementation with caution and under the guidance of a healthcare provider.

Consulting a healthcare provider before starting selenium supplementation is crucial, especially if you have existing medical conditions or are taking medications.

They can help determine the appropriate dosage based on your individual needs and monitor for any potential interactions or side effects.

Recommended Daily Intake by Age and Gender

The Dietary Reference Intakes (DRIs) for selenium, developed by the Food and Nutrition Board (FNB) at the National Academies of Sciences, Engineering, and Medicine, outline the recommended daily intakes for different age groups and genders to maintain optimal health. [2]

  • Birth to 6 months: 15 micrograms (mcg) per day for both males and females, based on the average intake of breastfed infants.
  • 7–12 months: 20 mcg/day for both males and females, continuing to support infancy growth and development.
  • 1–3 years: 20 mcg/day for toddlers, ensuring adequate selenium for early childhood growth and metabolic processes.
  • 4–8 years: 30 mcg/day for both boys and girls, supporting continued growth and development.
  • 9–13 years: 40 mcg/day for both males and females, meeting the increased nutritional demands of pre-adolescence.
  • 14–18 years: 55 mcg/day for teenagers, with slightly higher requirements for pregnant (60 mcg/day) and lactating (70 mcg/day) females due to increased metabolic demands during pregnancy and breastfeeding.
  • 19–50 years: 55 mcg/day for adults, maintaining steady intake for overall health and well-being.
  • 51+ years: 55 mcg/day for both men and women, ensuring adequate selenium for older adults.

These recommendations are designed to meet the nutritional needs of nearly all healthy individuals in each respective age group.

They provide a guideline for planning nutritionally adequate diets and ensuring optimal selenium intake to support various physiological functions, including antioxidant defense and thyroid hormone metabolism.

Risks and Side Effects of Selenium

While it is crucial for health, excessive intake can lead to adverse effects.

High doses of this nutrient supplements may cause nausea, diarrhea, and skin rashes. 

It's important to adhere to recommended daily intake levels and avoid exceeding safe limits to prevent selenium toxicity.

Selenium Deficiency and Overdose

Selenium deficiency is uncommon but can occur in individuals with poor dietary habits or certain medical conditions affecting nutrient absorption.

Symptoms of deficiency may include fatigue, muscle weakness, and changes in nail health.

Severe deficiency can lead to more serious health issues, such as cognitive decline and heart problems.

On the other hand, selenium overdose is rare but possible with excessive supplement intake.

Symptoms of selenium overdose may include gastrointestinal disturbances, hair loss, and neurological issues.

Following recommended intake guidelines and seeking medical advice can help prevent these complications.

Conclusion

In conclusion, selenium is a trace element essential for various physiological processes in the body, including antioxidant defense, thyroid function, and DNA synthesis.

While selenium offers potential health benefits, including cancer prevention and immune support, it's essential to obtain it from a balanced diet or supplements under healthcare guidance.

Understanding the risks, benefits, and recommended intake of selenium can help individuals make informed decisions to support their overall health and well-being.

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References

Rd, J. K. M. (2023a, February 6). 7 Science-Based Health benefits of selenium. Healthline. https://www.healthline.com/nutrition/selenium-benefits

Office of Dietary Supplements - selenium. (n.d.). [2] https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/

SELENIUM: Overview, uses, side effects, precautions, interactions, dosing and reviews. (n.d.). https://www.webmd.com/vitamins/ai/ingredientmono-1003/selenium

Shreenath, A. P., Hashmi, M. F., & Dooley, J. (2023, October 29). Selenium deficiency. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK482260/