The Role of Selenium in the Human Body: Benefits of Selenium for man and women

Introduction

Selenium is a trace mineral that plays a vital role in maintaining human health. Although the body requires it in small amounts, its functions are critical for immunity, thyroid health, reproduction, and protection against oxidative stress. Despite being less popular compared to other nutrients like iron, calcium, or vitamin D, selenium is indispensable. In fact, both deficiency and excess intake can lead to health problems, making it essential to maintain the right balance.

In this article, we will explore the role of selenium in the human body, its biological importance, health benefits, dietary sources, deficiency symptoms, recommended intake, and potential risks of overconsumption.

What is Selenium?

Selenium is a naturally occurring trace element found in soil, water, and certain foods. In the human body, it is a component of selenoproteins — specialized proteins that perform antioxidant and metabolic functions. These proteins help regulate hormonal activity, support DNA synthesis, and strengthen the immune system.

Biological Role of Selenium in the Human Body

1. Antioxidant Defense

Selenium is a key component of the enzyme glutathione peroxidase, which protects cells from oxidative stress caused by free radicals. By neutralizing these harmful molecules, selenium reduces the risk of cell damage, premature aging, and chronic diseases such as cancer and heart disease.

2. Thyroid Function

The thyroid gland contains more selenium per gram of tissue than any other organ. Selenium-dependent enzymes regulate thyroid hormone production, helping convert thyroxine (T4) into the active form triiodothyronine (T3). This conversion is essential for metabolism, energy regulation, and overall hormonal balance.

3. Immune System Support

Selenium boosts immune defense by enhancing the production of white blood cells and improving the body’s ability to fight infections. Research shows that individuals with adequate selenium levels respond better to vaccines and have lower risks of viral infections.

4. Reproductive Health

Selenium plays a role in male fertility by supporting sperm motility and preventing oxidative damage in reproductive tissues. In women, selenium helps in healthy egg maturation and protects against complications during pregnancy.

5. DNA Synthesis and Repair

Selenium contributes to genetic stability by aiding in the synthesis and repair of DNA. This role makes it crucial for preventing mutations that could lead to cancer or other genetic disorders.

Health Benefits of Selenium

1. Protection Against Heart Disease

Adequate selenium levels reduce oxidative stress and inflammation, two major contributors to heart disease. Studies suggest that selenium may lower the risk of cardiovascular problems by preventing cholesterol oxidation.

2. Cancer Prevention

Selenium’s antioxidant properties reduce DNA damage, which is a precursor to cancer development. Some clinical studies show that higher selenium intake is linked with reduced risks of certain cancers, particularly prostate, lung, and colorectal cancer.

3. Cognitive Health and Alzheimer’s Disease

Oxidative stress contributes to neurodegenerative diseases like Alzheimer’s. Selenium, through its antioxidant role, protects brain cells and supports cognitive function. Diets rich in selenium may reduce memory decline and improve overall brain health.

4. Anti-Inflammatory Properties

Chronic inflammation is at the root of many diseases. Selenium helps lower inflammatory markers, improving conditions like asthma, rheumatoid arthritis, and autoimmune thyroid disease (Hashimoto’s thyroiditis).

5. Healthy Pregnancy and Child Development

Selenium ensures proper fetal growth and reduces risks of complications such as preeclampsia, low birth weight, and miscarriage. Breast milk also contains selenium, which supports newborn immunity.

6. Skin and Hair Health

By reducing oxidative stress, selenium supports healthy skin and prevents premature aging. It also contributes to strong hair follicles and reduces dandruff when used in medicated shampoos.

Selenium Deficiency

Causes of Deficiency

Selenium deficiency is rare but can occur in areas where the soil is selenium-poor. Certain medical conditions like HIV, Crohn’s disease, or kidney dialysis also increase the risk.

Symptoms of Deficiency

Muscle weakness and fatigue
Weakened immunity
Hair loss and brittle nails
Cognitive decline
Thyroid dysfunction (hypothyroidism)
Infertility issues
Increased risk of Keshan disease (a heart condition linked to deficiency in selenium-deficient regions of China)

Sources of Selenium

1. Dietary Sources

The best way to maintain selenium levels is through diet. Foods rich in selenium include:

Brazil nuts (one of the richest sources)
Seafood (tuna, sardines, shrimp, salmon)
Meat and poultry (chicken, beef, turkey)
Eggs
Whole grains (brown rice, oats)
Dairy products
Mushrooms
Sunflower seeds

2. Supplements

Selenium is available in supplement form, often combined with multivitamins. However, supplements should be taken only under medical guidance because excessive intake can be harmful.

Recommended Daily Intake of Selenium

The Recommended Dietary Allowance (RDA) varies by age and gender:

Adults: 55 micrograms/day
Pregnant women: 60 micrograms/day
Breastfeeding women: 70 micrograms/day
Children: 20–40 micrograms/day depending on age

A single Brazil nut can contain up to 90 micrograms, so overconsumption should be avoided.

Risks of Excess Selenium (Selenosis)

Too much selenium can be toxic. Chronic high intake leads to a condition called selenosis, which causes:

Hair and nail brittleness
Nausea and vomiting
Skin rashes
Nervous system problems
Garlic-like odor in breath
Severe cases: organ failure or death

The upper safe limit for adults is 400 micrograms per day.

Selenium and Modern Research

Selenium and COVID-19:
Preliminary studies suggest that selenium may help in reducing the severity of viral infections, including COVID-19, by enhancing immune defense.
Selenium in Cancer Therapy:
Ongoing research investigates selenium’s role in cancer treatment, particularly in enhancing chemotherapy effectiveness.
Selenium and Diabetes:
Some studies show a link between selenium intake and blood sugar regulation, though findings are mixed.

Conclusion

Selenium, though required in trace amounts, plays an outsized role in maintaining human health. From protecting against oxidative stress and supporting thyroid function to enhancing fertility and immunity, selenium is indispensable. The key is balance — both deficiency and excess can cause health complications.

Maintaining adequate selenium levels through a diet rich in nuts, seafood, whole grains, and lean meats is the safest way to enjoy its benefits. With growing research highlighting its role in preventing chronic diseases, selenium truly stands out as one of the essential micronutrients for long-term health and well-being.