Selenium: Beneficial Role in Health, Sources And Side Effects

Zoomi Singh

October 12, 2022

Selenium is a trace mineral that you naturally find in the soil. Our body needs it in minimal amounts. Selenium is essential for reproduction, proper functioning of the thyroid gland, protection from infections, DNA synthesis, and protecting the cells from oxidative stress caused by free radicals. Brazil nuts contain the highest concentration of selenium. Other foods like nuts, seeds, meat and grains also contain reasonable amounts of selenium. Infant formulas are fortified with selenium to ensure babies receive them in adequate amounts.

Selenium concentration in food depends on the soil it grows in. 1817 is the year of its discovery, and it was initially considered a tellurium compound. However, it eventually got medical attention due to its toxicity to industrial employees. Selenium has also been poisonous to animals that consume high-selenium plants. So an excess of this can be potentially harmful to health. 

Despite selenium’s beneficial effects on human health, consuming it in required amounts is essential. However, taking excess selenium may result in adverse health outcomes.

Science-Based Health Benefits of Selenium

1. Reduces Risk of Prostate Cancer

Many factors such as old age, obesity, genetics can play a role in developing prostate cancer. In addition, people with prostate cancer may suffer from loss of bladder control, erectile dysfunction and so on. 

A research study found that adequate selenium levels in the body reduce the risk of developing prostate cancer amongst males. Selenium prevents prostate cancer by slowing the development and spread of cancer cells. Selenium levels in the blood and tissues are all inversely related to the risk of prostate cancer.

Research has also shown that selenium reduces the risk of several other cancers such as breast, colon and lung cancers.

2. Selenium Contains Antioxidative Properties

The production of free radicals in our body results from exposure to toxins in the environment. In addition, metabolic functions in the body also produce them. When the production of these free radicals is in excess, they harm the tissues and organs. Antioxidants play an essential role in reducing the damage caused by free radicals in the body. For example, selenium is a well-known antioxidant nutrient.

A study demonstrates that selenium intake might reduce the markers of oxidative stress. In addition, it increases the antioxidative activity, thereby reducing the free radical damage.

3. Reduces Risk of Heart Disease

We know that heart disease occurs due to poor dietary habits, genetics, lack of physical activity, smoking, high cholesterol levels and many other reasons. If not treated, it results in several serious health outcomes such as stroke, cardiac failure, etc.

Studies have shown that selenium intake is associated with a reduced risk of heart disease. Selenium is a potent antioxidant. It acts on the heart by protecting it against the damage caused due to free radicals. Selenium also works by reducing inflammation by preventing oxidative damage to the lipids and clogging of arteries. Therefore, selenium reduces the risk of heart disease and stroke.

4. Selenium Delays Onset of Alzheimer’s Disease

Alzheimer’s disease occurs when a decline in brain function results in memory loss. The most common causes of Alzheimer’s disease are lifestyle, environment and genetics. As the condition worsens, it can cause difficulties in speaking, learning and remembering.

Different states of selenium have neuroprotective effects. A study demonstrates that selenium’s antioxidant properties help protect the brain from damage due to free radicals. Thereby, it delays the development of Alzheimer’s disease.

The Mediterranean diet popularly used in many diseases includes foods rich in selenium such as nuts, seeds and seafood. These foods are also beneficial in reducing the risk of Alzheimer’s disease.

5. Helps Treat Thyroid Disorders

Thyroid hormone fluctuation leads to hypothyroidism, Grave’s disease, Hashimoto’s thyroiditis, etc. In addition, your growth and development can be affected if your thyroid gland does not function properly. For example, it may result in hair loss, weight loss, irregular menstrual cycle, slow growth, tiredness and many more.

The thyroid gland contains the highest amounts of selenium in its tissues. As we already know, metabolic functions such as the secretion of thyroid hormones can produce free radicals. Selenium protects the thyroid gland from oxidative stress. A study has found that selenium may improve thyroid disorders.

6. Reduces Inflammation

Selenium improves the immune response. A study found that the selenoprotein formed from dietary selenium reduces the inflammatory response. These are associated with several diseases such as allergy, asthma, inflammatory bowel disease, etc. It acts by decreasing the over-activation of the immune system. It also strengthens the body’s immunity against infectious pathogens that cause influenza and tuberculosis.

7. Aids in Weight Loss

Unhealthy weight gain can lead to several health issues such as obesity and heart disease. Selenium plays a vital role in metabolism as it regulates the functions and secretion of thyroid hormones. A study shows that adequate selenium intake may help maintain a healthy metabolic rate. Therefore, appropriate amounts of selenium intake lead to weight loss. However, when taken above the standard requirements, selenium can have quite the opposite effect.

8. Selenium Improves Skin Health

The predominant cause of rapid skin ageing is exposure to sunlight, smoke and other environmental pollutants. It can result in the development of acne, wrinkles and dull skin.

Studies have found selenium to be beneficial in preventing and treating skin problems such as psoriasis. It has antioxidant properties. Hence, selenium protects the skin from oxidative damage caused by sun exposure.

9. Prevents Premature Birth

Nutrients such as zinc, selenium, iron, folate are essential for the healthy growth and development of the baby during pregnancy. Studies have found that selenium is crucial for a baby’s healthy birth. Intake of appropriate amounts of selenium prevents adverse pregnancy outcomes such as premature birth and foetal growth restriction.

10. May Improve Fertility

Some research studies suggest that selenium intake improve fertility in women. In addition, selenium helps enhance reproductive function by keeping follicular fluid healthy. It is also beneficial in improving sperm count and motility in men.

Selenium Deficiency

Selenium is essential for the proper functioning of the thyroid gland and many other systems in our body. Low levels of selenium may disrupt the normal processes and may lead to:

  • Fatigue
  • Hair loss
  • Brain fog
  • Weakened immunity
  • Weak muscles
  • Infertility 

The deficiency of selenium can lead to specific disease conditions. 

Keshan Disease

Keshan disease is a dangerous disorder that, if left untreated, can lead to cardiovascular disease, stroke, or death. You can treat Keshan disease or control it, but it is not curable. It commonly occurs in women and children. Studies suggest that it can occur due to selenium deficiency. Sometimes it is combined with microbial infection.


  • Nausea
  • Vomiting
  • Loss of appetite
  • Dizziness
  • Chills
  • Irregular heartbeat
  • Fatigue
  • Inflammation
  • Hair loss

In worst cases, it may lead to severe complications, such as:

  • Cough with blood
  • Severe shortness of breath
  • Congestive heart failure
  • Fainting
  • Palpitation
  • Stroke

Kashin Disease

It is a joint and bone disorder associated with low selenium levels. However, the cause of this disease is also due to other factors. It commonly occurs in children. Studies show that people affected with this disease generally have decreased growth and bone abnormalities.


  • Pain and stiffness in joints
  • Inability to move joints
  • Enlarged joints

People of all age groups should take the recommended doses of selenium. It will help them with proper growth and development. However, it is essential to ensure that you do not consume in excess. Also, it is preferable to take selenium along with a meal rather than on an empty stomach. The recommended intake should be:

  • 0-6 Months: 15mcg
  • 7 months-3 years: 20mcg
  • 4-8 years: 30mcg
  • 9-13 years: 40mcg
  • 14 years and above: 55mcg
  • Pregnant women: 60mcg
  • Breastfeeding women: 70mcg

Food Sources of Selenium

Selenium: Beneficial Role in Health, Sources And Possible Side Effects- HealthifyMe

1. Brazil Nuts

They are rich in nutrients and antioxidants. Brazil nuts have the highest selenium content and contain reasonable amounts of zinc. In addition, a study shows that consuming a single serving of Brazil nuts can acutely improve the serum lipid profile of healthy volunteers. That is because they are nutritious and help improve heart health. They also support the healthy functioning of the other organs, such as the brain and kidneys.

Nutritional Values

As per USDA, 100g of brazil nuts contain:

  • Energy: 659kcals
  • Carbohydrates: 11.7g
  • Protein:14.3g
  • Fat: 67.1g
  • Fibre:7.5g
  • Calcium: 160mg
  • Iron: 2.43mg
  • Zinc: 4.06mg
  • Selenium: 1920µg

2. Tuna

Tuna is an excellent source of high-quality protein. It is low in calories and fat and helps build muscle while reducing body fat. In addition, they are highly nutritious as they contain reasonable amounts of calcium, B complex vitamins, etc.

Nutritional Values

As per USDA, 100g of tuna contains:

  • Energy: 85kcals
  • Carbohydrates: 0.08g
  • Protein:19g
  • Fat: 0.6g
  • Calcium: 18mg
  • Iron: 1.67mg
  • Zinc: 0.66mg
  • Selenium: 67.8µg

3. Turkey

Turkey is another high protein yet low carb food. It is full of B complex vitamins, zinc and selenium. It can make a delicious and healthy side to most of your lunch dishes.

Nutritional Values

As per USDA, 100g of turkey contains:

  • Energy: 213kcals
  • Carbohydrates: 0g
  • Protein:27.1g
  • Fat: 10.4g
  • Calcium: 31mg
  • Iron: 1.56mg
  • Zinc: 3.77mg
  • Selenium: 28.4µg

4. Cottage Cheese

Cottage cheese is a type of curd cheese. It is delicious and healthy and has low fat, high protein, selenium, calcium and many other nutrients. You can add them to your salads, eggs, toast, and so much more.

Nutritional Values

As per USDA, 100g of cottage cheese contains:

  • Energy: 82kcals
  • Carbohydrates: 4.31g
  • Protein: 11g
  • Fat: 2.3g
  • Calcium: 103mg
  • Iron: 0.13mg
  • Zinc: 0.61mg
  • Selenium: 14.6µg

5. Sunflower Seeds

Sunflower seeds help regulate the menstrual cycle, reduce heart diseases, and improve immunity. However, they are high in calories, and you should consume them in moderation.

Nutritional Values

As per USDA, 100g of sunflower seeds contain: 

  • Energy: 657kcal
  • Carbohydrates: 17.1g
  • Protein: 21g
  • Fat: 56.1g
  • Calcium: 78mg
  • Iron: 5.2mg
  • Zinc: 6mg
  • Selenium: 80.4µg

Possible Side Effects & Precautions of Selenium

Taking selenium supplements according to a physician’s prescription is advisable. However, it is essential to be cautious. Intake should not cross the safe upper limits. These upper limits are:

  • 0-6 months: 45mcg
  • 7-12 months: 46mcg
  • 1-3 years: 90mcg
  • 4-8 years: 150mcg
  • 9-13 years: 280mcg
  • 14 years and above: 400mcg

Thyroid Disorders

Taking selenium might make hypothyroidism worse. It occurs mainly in persons who are deficient in iodine. In this case, you should take iodine and selenium together. Consult your physician for appropriate dosage and treatment.

Sperm Motility

Though studies suggest selenium improves fertility, it is essential to note that taking selenium in excess can have the opposite effect. It is because selenium limits the capacity of sperm to move, thereby lowering fertility. Therefore, consume selenium within the tolerable upper limits only.

Selenium can Cause Kidney Disease

Excessive intake of selenium can be potentially harmful to the kidney. Therefore, it is essential to consume selenium within safe limits in patients with kidney failure or people undergoing dialysis. Studies have found that excessive selenium intake may result in acute renal failure.


Case studies have found that high levels of selenium intake may lead to congenital disabilities in babies. It may also lead to complications in the pregnancy. Hence, it is essential to consume selenium within tolerable limits.

Other Medications

Selenium supplements interfere with a few medications when taken together. One such medication is warfarin. Studies show that selenium may alter the activity of warfarin. Therefore, it would help if you discussed with your physician before consumption.


Studies show that selenosis occurs due to a high selenium intake. For example, it can be due to increased consumption of selenium-rich foods such as brazil nuts. It may also occur due to foods grown in soil with high selenium content or excessive selenium supplementation.


  • Nausea
  • Vomiting
  • Discolouration of nail
  • Brittle nails
  • Hair loss
  • Fatigue
  • Irritability
  • Foul odour or ‘garlic breath.’

The Bottom Line

Selenium is crucial for day to day functions performed by our body. However, excess intake of selenium can lead to harmful effects. Both selenium deficiency and toxicity can contribute to adverse health outcomes. Therefore, it is essential to be cautious when opting for a selenium supplement. One should always consult a physician and discuss the benefits and side effects of taking a supplement. It is also essential to steer clear of any drugs interacting with selenium supplements.

Frequently Asked Questions (FAQs)

1. What does selenium do for the body?

A. Selenium plays a significant role in the proper functioning of the thyroid gland, reproductive system and protects the body from infections. In addition, it helps improve skin and heart health and helps improve skin.

2. Is it safe to take selenium every day?

A. Yes, you can take selenium safely every day as long as it remains within the tolerable upper limit. Above the safe limit may be harmful to the body. It may cause adverse effects such as nausea, vomiting, irritability, etc.

3. What are the symptoms of selenium deficiency?

A. Selenium deficiency can cause symptoms like weak immunity, hair loss, muscle weakness, nausea, vomiting, fatigue, infertility and brain fog.

4. How much selenium should you take daily?

A. You can consume selenium-rich foods like brazil nuts, chicken, turkey and tuna to get an adequate amount of selenium. The recommended dose varies as per age and medical conditions. It is as follows:

  • 0-6 Months: 15mcg
  • 7 months-3 years: 20mcg
  • 4-8 years: 30mcg
  • 9-13 years: 40mcg
  • 14 years and above: 55mcg
  • Pregnant women: 60mcg
  • Breastfeeding women: 70mcg

5. What is the side effect of selenium?

A. Selenium imparts various health benefits to you when taken in moderation. However, an increased selenium intake can result in adverse health outcomes such as foul odour or “garlic breath”, discolouration of nails, brittle nails, nausea, vomiting, fatigue and hair loss.

6. Does selenium cause weight gain?

A. No, consuming selenium in adequate amounts helps in losing weight. It is due to selenium’s role in regulating thyroid function and metabolism. However, some studies have shown that excessive intake of selenium may cause an increase in weight. 

7. What foods are high in selenium and zinc?

A. Foods such as brazil nuts, chicken, turkey, tuna and cottage cheese are selenium-rich foods. In addition, foods like meat, shellfish, legumes, seeds, nuts, dairy and some vegetables are excellent sources of zinc.

8. Is selenium good for the prostate?

A. Yes, selenium delays and reduces the risk of prostate cancer. It works by preventing the growth and spread of cancerous cells to other organs and tissues. Selenium levels in the blood and tissues are all inversely related to the risk of prostate cancer.

9. What time is best to take selenium?

A.You can take it at any time of the day. However, you should consume selenium supplements with other foods and not on an empty stomach.

10. Is selenium suitable for sperm production?

A. Yes, studies have found that taking an adequate amount of selenium can improve sperm motility and count in men. In addition, selenium helps enhance reproductive function by keeping follicular fluid healthy.

11. Can selenium raise PSA?

A. No, Studies have found that consumption of appropriate amounts of selenium can reduce PSA, thus reducing the risk of prostate cancer.

About the Author

Zoomi, holds Masters degree in Nutritional Sciences from University of Allahabad, qualified CBSE-UGC-NET in Home Science and pursuing PhD in Nutritional Sciences, University of Allahabad, Prayagraj. A Strong research professional focused in Nutritional Sciences where she have more than 8 yrs of work experience in the field of Nutrition and Research, had work experience as a Dietician at Super-specialty hospitals. Skilled in Weight Management, Hypertension, Diabetes and Micronutrient related deficiencies. Additionally, she is well-versed in biostatistics and proficient in statistical tools such as SPSS and STATA. She is endowed with strong writing abilities and has authored her own book, more than six research papers, and six book chapters. Holder of various awards like Excellent Dietician, 2019 and 2020 by Saksham Society, Jaipur, Rajasthan, Academic Excellence at National Conference by Jayoti Vidyapeeth Women’s University, Jaipur (Rajasthan), India and Research Achievement Award-2020 for Research & Innovation by ACAIRS Global Network Pvt. Ltd. Life Member of Nutrition Society of India, NIN, Hyderabad and participated and presented papers in four International and six National conferences. Zoomi believes the right habits play the most crucial role in one’s health and wellness journey. The key to fit body is a fit mind and mental state.

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