Nutrition Diet: What are the signs of selenium deficiency?

October 1, 2025 •

4 min read

The selenium content in food is directly influenced by the mineral levels of the soil where it's grown, meaning dietary intake can vary significantly by geographic location. Recognizing what are the signs of selenium deficiency is the first step toward correcting an imbalance in this essential trace mineral.

Quick Summary

Selenium deficiency manifests in a variety of symptoms, including fatigue, cognitive issues, hair and nail changes, and muscle weakness. It can also impact thyroid function, immune response, and fertility. Understanding the causes and risk factors is crucial for prevention and management.

Key Points

Fatigue and Weakness: Persistent tiredness and muscle weakness are primary indicators of a selenium shortage.
Hair and Nail Changes: Thinning hair, hair loss, or brittle, discolored nails can signal a deficiency.
Weakened Immune Response: Frequent infections and illness may point to a compromised immune system due to low selenium.
Thyroid Dysfunction: A selenium deficiency can contribute to hypothyroidism by disrupting thyroid hormone metabolism.
Cognitive and Mood Issues: Mental fog, memory problems, anxiety, and depression are associated with insufficient selenium.
Reproductive Challenges: Infertility in both men and women has been linked to inadequate selenium intake.
Diverse Food Sources: Incorporating foods like Brazil nuts, seafood, meats, and eggs can help prevent or correct a deficiency.

The Importance of Selenium

Selenium is a powerful trace mineral that plays a vital role in human health. It is a key component of selenoproteins, a group of enzymes that act as potent antioxidants, protecting cells from oxidative damage caused by free radicals. These selenoproteins are essential for critical bodily functions, including thyroid hormone metabolism, DNA synthesis, and reproduction. A deficiency can disrupt these processes, leading to a wide range of noticeable symptoms that can affect your overall well-being.

Common Physical Signs of Low Selenium

One of the most frequently reported symptoms of low selenium levels is persistent weakness and fatigue. Because selenium is involved in cellular energy metabolism, a shortage can result in a significant drop in energy levels, making even simple daily tasks feel exhausting. The effects of a deficiency can also become visible externally.

Hair and Nail Abnormalities

Hair Loss: Selenium is necessary for healthy hair growth. A deficiency can lead to hair thinning or loss.
Nail Discoloration: Brittle or discolored nails, sometimes with white spots or bands (leukonychia), can indicate inadequate selenium intake.

Muscle Weakness and Pain

Many people with a selenium deficiency experience muscle pain and tenderness. In severe cases, this can lead to myopathy, or muscle disease, characterized by atrophy and impaired muscle contraction. This can impact mobility and overall physical strength.

Weakened Immune System

Selenium is critical for a robust immune system. Inadequate levels can suppress immune function, leaving the body more susceptible to viral and microbial infections. People with a deficiency may experience frequent colds and a longer recovery time from illnesses.

Deeper Health Implications

While some signs of selenium deficiency are noticeable, others affect underlying biological systems, leading to more serious health issues.

Thyroid Dysfunction

Selenium is highly concentrated in the thyroid gland, where it helps regulate the metabolism of thyroid hormones. A deficiency can disrupt this process and contribute to conditions like hypothyroidism, characterized by fatigue, weight gain, and mood swings. It has also been associated with autoimmune thyroid conditions like Hashimoto's thyroiditis.

Reproductive Issues

For both men and women, selenium is vital for reproductive health. Low levels can contribute to male infertility by affecting sperm motility and quality. In women, a deficiency can be linked to gestational complications, miscarriages, and preeclampsia.

Cognitive Decline and Mood Disorders

The brain preferentially retains selenium during times of scarcity, highlighting its importance for neurological function. An insufficiency has been linked to impaired cognitive function, including poor memory and mental fog. Low selenium status is also associated with a higher risk of mood disorders, such as anxiety and depression.

Extreme Cases: Keshan and Kashin-Beck Diseases

In regions with extremely low selenium soil, such as parts of rural China, two serious diseases have been historically linked to severe selenium deficiency: Keshan disease, a form of cardiomyopathy affecting the heart, and Kashin-Beck disease, a degenerative joint and bone disorder. While rare in other areas, these diseases demonstrate the profound impact of profound deficiency.

Factors Contributing to Selenium Deficiency

Several factors can put an individual at risk of developing a selenium deficiency:

Dietary Intake: The most common cause is a diet lacking in selenium-rich foods, often due to low soil selenium content where crops are grown.
Geographic Location: The mineral content of soil varies globally, and populations in certain regions are at higher risk.
Vegan and Vegetarian Diets: Without careful planning, plant-based diets can be lower in selenium compared to animal-based diets.
Gastrointestinal Disorders: Conditions like Crohn's disease, celiac disease, and ulcerative colitis can impair nutrient absorption, including selenium.
Medical Treatments: Long-term total parenteral nutrition (TPN) or certain surgical procedures can reduce selenium absorption.

Dietary Solutions and When to Seek Medical Advice

Fortunately, increasing selenium intake through diet is an effective treatment for most cases of deficiency. Medical professionals can diagnose the condition through blood tests that measure selenium and selenoprotein levels.

High-Selenium Food Sources

Brazil Nuts: Just one or two Brazil nuts can provide the recommended daily allowance.
Seafood: Yellowfin tuna, sardines, and shrimp are excellent sources.
Meats: Beef steak and poultry are also high in selenium.
Eggs and Dairy: These products offer a good amount of the mineral.
Whole Grains and Beans: These are also a source, though levels can depend on the soil.

Selenium Sufficiency vs. Deficiency


Symptom	Selenium Sufficiency	Selenium Deficiency
Energy Levels	High and stable	Persistent fatigue and weakness
Hair & Nails	Strong and healthy	Brittle, thinning, or discolored hair and nails
Immune System	Strong resistance to infections	Frequent illness and poor immune function
Muscle Health	Normal strength and function	Weakness, aches, and muscle pain
Cognitive Function	Clear, focused mind	Mental fog, poor concentration, and memory issues
Thyroid Function	Balanced thyroid hormone levels	Hypothyroidism and other thyroid dysfunction
Mood	Stable mood	Increased anxiety, confusion, and depression

Conclusion

Understanding the subtle and significant changes that can signal a deficiency is vital for maintaining optimal health. Because selenium plays such a critical role in antioxidant defense, thyroid regulation, and immune function, recognizing what are the signs of selenium deficiency allows for prompt dietary changes or, if necessary, medical intervention. If you experience persistent symptoms like fatigue, hair loss, or weakened immunity, consult a healthcare provider to assess your selenium status. By ensuring adequate intake, you can support your body's essential functions and enhance your overall well-being.

For more detailed information on nutrient functions and dietary guidelines, consider consulting authoritative sources such as the NIH Office of Dietary Supplements fact sheets.

Frequently Asked Questions

Early signs of selenium deficiency often include persistent fatigue, muscle weakness, and a general feeling of being run down. You might also notice more frequent colds or infections due to a weakened immune system.

Selenium deficiency can manifest as thinning hair, hair loss, or brittle and discolored nails. Nail abnormalities such as white spots or bands are also commonly observed.

Yes, selenium is crucial for proper thyroid function. A deficiency can interfere with the metabolism of thyroid hormones and may contribute to conditions like hypothyroidism.

Low selenium has been associated with cognitive decline, including mental fog, difficulty concentrating, and memory issues. The brain relies on this mineral for healthy neurological function.

Yes, people following strict vegetarian or vegan diets can be at a higher risk of selenium deficiency because plant-based foods often contain lower levels of the mineral compared to animal products, and the selenium content in plants depends on the soil.

Diagnosis is typically based on a review of symptoms, dietary habits, and medical history. A blood test can measure selenium levels in the blood, and tests for thyroid function may also be performed.

Some of the best dietary sources of selenium include Brazil nuts, seafood (tuna, sardines), meat, poultry, eggs, whole grains, and dairy products. Brazil nuts are particularly potent sources.