Selenium

Selenium is a natural essential mineral belonging to the supplement class.

Selenium is also known as selenocysteine, selenide, selenite, selenate, and selenocyanate.

Selenium is an essential mineral that is required for the production of active thyroid hormones, immune system health, cognitive function, and antioxidant activity.

Selenium deficiency can negatively impact human development and reproduction.

Myodegenerative disorders, such as muscular weakening, are influenced by moderate deficiency. Depression, anxiety, and confusion are caused due to low selenium.

Brazil nuts, spinach, green peas, beans, potatoes, fish, chicken, and organ meats are some of the best food sources of selenium. Dairy products, breakfast cereals, and other grains are other sources.

Selenium is absorbed in the small intestine, transported throughout the body by proteins, incorporated into selenoproteins, and expelled through the urine and faeces.

The common side effects of selenium include nausea, vomiting, diarrhoea, and garlic-like breath odour.

Selenium is available in tablets, capsules and injectable solutions.

Biochemical action of selenium

Selenium belonging to the supplement class helps in maintaining a healthy immune system. Selenium acts via the selenoprotein biosynthesis pathway.

Selenium functions in several ways, frequently absorbed into selenoproteins. There are approximately 25 of these selenoproteins in human tissues, and they all have different processes. Selenium has significant effects on molecules, including glutathione peroxidases, which catalyse the reduction of peroxides, thioredoxin reductase, which helps with DNA synthesis; and deiodinase enzymes, which control thyroid hormones. Despite its ability to lower thyroid peroxidase antibodies, the effectiveness of selenium in treating Hashimoto's thyroiditis is yet unclear.

Selenium as a cofactor for glutathione peroxidase, selenium reduces oxidative stress through cellular metabolism.

Selenium and vitamin E together protect cell membranes and organelles from oxidative damage. As a result, selenium may enhance the immune system and host defence.

Selenium is available in tablets, capsules and injectable solutions.

• Tablets/capsules: To be swallowed whole with water/liquid, as applicable.
• Injectable solutions: To be administered parenterally, as applicable.

Selenium can be used as a supplement when the amount of selenium taken from the diet is insufficient.

Selenium supplement helps in treating dermatologic conditions

Adequate oral intake of Selenium supplements during pregnancy might reduce the risk of developing pre-eclampsia.

A selenium supplement helps in protecting the body against infection and free radical damage.

Vitamins and natural supplements should not replace a balanced diet.

This product is not intended to diagnose, treat or prevent any disease(s).

Selenium may be useful as a supplement for the following health benefits:

• Thyroid disease: High levels of selenium in the thyroid gland are essential for thyroid function. According to studies, individuals with low blood levels of selenium (and iodine), particularly women, may experience thyroid problems. However, it is unclear whether selenium dietary supplements can assist in treating or lowering the risk of thyroid illness. The effects of selenium on thyroid disease require further study.
• Cancer: According to studies, people who consume less selenium may be more likely to get cancers of the colon, rectum, prostate, lung, bladder, skin, oesophagus, and stomach. But it's unclear if selenium supplements lower cancer risk—the effects of selenium from food and dietary supplements on cancer risk warrant further research.
• Cardiovascular disease: Selenium may help lower the risk of cardiovascular disease, according to research conducted by scientists. There is conflicting evidence about the association between decreased blood levels of selenium and an increased risk of heart disease.
• Cognitive decline: Blood selenium levels decrease with ageing, and researchers are investigating whether low selenium levels in older people can lead to a deterioration in brain function. According to several research, individuals with lower blood selenium levels are more likely to have impaired mental performance.

Selenium supplementation may be administered orally or parenterally.

• Orally: Selenium supplements are available as tablets and capsules that can be taken orally. It is best taken with a meal or food.
• Parenterally: Selenium supplements are generally taken by mouth but may have to be administered intravenously to all patients who require parenteral nutrition (PN).

The dosage and duration of treatment should be as per the clinical judgment of the treating healthcare professional).

Vitamins and natural supplements should not replace a balanced diet

This product is not intended to diagnose, treat or prevent any disease(s).

Selenium is available in tablets, capsules and injectable solutions.

Selenium should be used as a supplement for maintaining strong immune function, a healthy thyroid, and appropriate dietary restrictions.

• Avoid alcoholic beverages.
• Stay within your daily calorie needs.
• Avoid smoking cigarettes.
• Limit foods and beverages higher in added sugars, saturated fat, and sodium.

The dietary restriction should be individualized as per patient requirements.

Recommended Daily Allowance (RDA)

The RDA of selenium is 55 mcg.

Upper Tolerable Intake (UTL):

The UTL set for selenium is 400 mcg.

Selenium supplementation may be contraindicated in the following conditions:

• Hypersensitivity; sensitive to selenium
• Autoimmune conditions such as multiple sclerosis, systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA) are contraindicated.
• Under-active thyroid (hypothyroidism)
• Surgery
• Having a history of non-melanoma skin cancer and prolonged use of selenium supplements may slightly raise the chance of cancer recurrence.

For individuals on hemodialysis, selenium from supplements might need to be absorbed better.

HIV-positive individuals are more susceptible than non-positive individuals to develop selenium deficiency.

Men should use selenium supplements with caution since they may impair sperm motility and decrease fertility.

Caution is advised when consuming alcohol with Selenium.

Unsafe to use during pregnancy.

Limit the consumption of foods and drinks higher in added sugars, saturated fat, sodium, and alcoholic beverages, as these substances could hinder selenium absorption.

Selenium is generally well-tolerated.

The adverse reactions related to selenium can be categorized as-

• Common: Redness, burning, itching, stinging, scalp sores, increased oiliness, nail hyperpigmentation, skin irritation and creating contact dermatitis.
• Less Common: Fatigue, hair loss, nail brittleness, mood changes or irritability.
• Rare: Allergic reactions, skin rash, metallic taste in the mouth, nervous system abnormalities, organ failure and death.

The clinically relevant drug interactions of selenium are briefly summarized here:

• Anticoagulant / Antiplatelet drugs: Blood coagulation may be slowed by selenium. When selenium is used with medications that slow down blood clotting, the risk of bleeding and bruises may increase.
• Niacin: Niacin and simvastatin's adverse effects on good cholesterol levels can be reduced by taking them along with selenium and other antioxidants. It is unclear if selenium lowers the effects of niacin and simvastatin on levels of good cholesterol.
• Barbiturates: Selenium can reduce the body's metabolism of sedative drugs. Combining selenium with these drugs could increase their effects and side effects.
• Warfarin: Blood coagulation may be slowed by selenium. Selenium may increase warfarin's physiological effects. Combining selenium with warfarin may make it more probable for bruising and bleeding.
• Immunosuppressants: The immune system's activity can be boosted by selenium. Some drugs, such as those prescribed after a transplant, reduce the immune system's function. The effects of these drugs may be decreased by taking selenium along with them.
• Contraceptive drugs: Using birth control tablets may raise selenium levels in the blood. But it's unclear whether this is a serious concern.
• Gold salts: Selenium is reduced in several regions of the body when gold salts bind to it. This might minimise selenium's usual action, which can lead to selenium shortage symptoms.

• Cisplatin: Although this cancer medication may reduce selenium levels, it is unclear how this will affect the body.

The common side of Selenium includes the following:

• Nausea
• Vomiting
• Diarrhea
• Garlic-like breath odour.
• Stomach discomfort
• Headache
• Rash
• Weight loss

The use of Selenium should be prudent in the following group of special populations.

• Pregnancy:

Pregnancy Category: C. Safe during pregnancy, but when taken in high doses, use with caution if the benefits outweigh the risks.

The RDA for Selenium in pregnant women is 60 mcg/day.

• Paediatrics:

Selenium supplements are essential for children in maintaining the heart and blood vessels. It also preserves the health of the skin and cardiac muscle. It might help in the treatment and prevention of cancer.

Selenium supplements are the best way to help children get enough selenium daily.

The RDA for selenium in paediatrics ranges from 15-55 mcg/day.

Dosage Adjustment for Paediatric Patients

There are no specific dosage adjustments provided.

• Geriatrics:

There is no sufficient scientific evidence traceable regarding the use and safety of selenium for use in special populations.

• Lactating mothers:

When consumed more than RDI, Selenium may excrete in breast milk and harm a breastfeeding infant, so it is advised to use it cautiously.

The RDA for Selenium in lactating mothers is 70 mcg/day.

Dosage Adjustment in Kidney Impairment

There are no specific dosage adjustments provided.

Dosage Adjustment in Hepatic Impairment

There are no specific dosage adjustments provided.

Dosage Adjustment for Adult Patients

Supplementation

100-200 mcg/day PO with meals (preferably); may take 50 mcg PO qDay or q6hr

The physician should be vigilant about the knowledge pertaining to identifying and treating the overdosage of selenium. Overdosing on selenium supplements may cause symptoms like hair loss, fatigue, and nervous system issues.

There is no specific antidote or treatment for excessive intake of supplemental selenium. Selenium should be terminated immediately if an overdose occurs. Supportive treatment should also be given, along with addressing any symptoms that persist or worsen. Physical therapy might be added if necessary.

Biochemistry profile of Selenium

As a component of the bacterial and animal enzymes glutathione peroxidase, selenium plays a unique biological chemistry. Due to its existence as the 21st amino acid, selenocysteine, it is the only (semi)metal trace element genetically encoded for protein integration, which differs from its uncommon in humans considering its vital function. Currently, 25 selenoproteins have been identified in the human proteome, each having a unique process. Others support antioxidant defence, redox state management, and specific metabolic pathways, while some roles are unknown. Interestingly, Selenoproteins are being considered possible biomarkers for disorders including diabetes and other cancers. Understanding selenium's metabolic pathways in typical biological conditions becomes essential to take advantage of its potential for treating and preventing human illnesses.

Kinetic profile:

• Absorption: The small intestine is where selenium is absorbed most readily. It is typically absorbed as the selenium-containing amino acids selenomethionine and selenocysteine. Absorption efficiency could differ based on dietary factors such as the type of selenium and the presence of other minerals.
• Distribution: Once ingested, selenium is predominantly carried in the circulation attached to proteins like albumin and selenoproteins. It distributes throughout the body's tissues, with higher levels seen in the thyroid gland, liver, kidney, and muscles. For selenium to be incorporated into selenoproteins, which are required for many biological functions, the distribution is essential.
• Metabolism: Selenium gets integrated into selenoproteins during metabolism. These proteins include a unique amino acid called selenocysteine, which contains selenium. The formation of selenoproteins, many of which serve as enzymes with antioxidant and other significant roles in cellular processes, is directly related to the body's selenium metabolism.
• Elimination: Selenium is mainly excreted in the urine, although a significant amount is also eliminated in the faeces. By filtering excess selenium from the blood and passing it into the urine, the kidneys are crucial in controlling the body's selenium levels.

1. https://www.ncbi.nlm.nih.gov/books/NBK557551/
2. https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/
3. https://ods.od.nih.gov/factsheets/Selenium-Consumer/

4. National Institute of Nutrition. 2011. Dietary guidelines for Indians; 2nd Edition. Hyderabad. India

5. https://www.fssai.gov.in/upload/advisories/2021/07/60f1798019f94Direction_RDA_16_07_2021.pdf