Selenium is one of the micronutrient minerals in the body. It is thus needed in very small amounts. Too much of it will lead to serious health issues, while inadequate amounts will also increase the risk of other health conditions related to the deficiency of the mineral.
Selenium is an essential nutrient which means it has to be sourced from the food we eat. It is found naturally in some foods while some processed foods have the mineral added to it. It is also commonly found as an ingredient in some multi-mineral-multivitamin nutritional supplements.

This mineral exists in two forms.

  • In an inorganic form – selenite
  • In an organic form – selenomethionine

Plants convert the inorganic form from the soil to the organic type.
Selenium is mainly stored in the muscles and the liver but is also present in smaller amounts in other body tissues.

Functions of selenium in the body

Selenium is part of many proteins (called selenoproteins) that are vital in:

  • Reproduction
  • Thyroid health
  • DNA integrity
  • Antioxidant protection
  • Immune support
  • Prevents oxidative damage to cells (antioxidant)

Signs and symptoms of deficiency

Selenium deficiency can lead to biochemical changes in the body. If this situation is complicated by the presence of other health conditions, serious complications can occur. An example is a heart condition called Keshan disease. This problem occurs when selenium deficiency is compounded by a viral infection. Some types of male infertility have also been associated with the mineral’s deficiency. Other signs and symptoms include:

  • Impaired memory
  • Chronic fatigue
  • Recurrent common infections such as the cold and flu
  • Fertility problems
  • Poor wound healing
  • Hair discoloration or loss
  • Unhealthy fingernails
  • Signs and symptoms of hypothyroidism
  • Untreated and persistent selenium deficiency can lead to mental and physical retardation, heart disorders, allergic disorders such as asthma, rheumatoid arthritis and other inflammatory issues can also develop.

Overt selenium deficiency is rare. However, some peoples may be at risk of having subclinical deficiency which can lead to general ill-health.

Risk factors for selenium deficiency

  • Patients on parenteral feeding
  • Women of childbearing age
  • Gastric surgery (especially where gut resection is performed)
  • Those living in places with low natural selenium in the soil
  • Those on dialysis
  • Immunosuppressed patients

Selenium deficiency can bring an imbalance in other minerals in the body. One study suggested that such a deficiency can lead to imbalance in iron, zinc, copper, magnesium, and calcium

Sources of selenium

The two main sources of selenium are plant and animal-based foods. Another assured source is the use of nutritional supplements. Plant sources include:

  • Brazil nuts are among the highest (if not the highest) selenium containing foods.
  • Mushrooms
  • Legumes such as lima beans
  • Unpolished (brown) rice
  • Chia seeds
  • Cabbages
  • Broccoli
  • Spinach
  • Cooked plantains
  • Brussel sprouts
  • Soybeans
  • Asparagus
  • Whole grains
  • Bananas
  • Oat bran
  • Sunflower seeds

Selenium nutritional supplements

These are available in several forms. They can be in:

  • Sodium selenite
  • Sodium selenate
  • Selenomethionine
  • Selenium fortified yeast

Regions at risk of selenium deficiency can benefit from foods fortified with selenium.

It is important to know that these selenium compounds can be organic or inorganic. Both these forms can be converted in the body to a form that is bioavailable but the organic type is more readily available.

How can you tell that the selenium in a dietary supplement product is of organic origin? It is indicated as L-selenomethionine. The selenium in Essential is thus labeled.

Health benefits of selenium

From the above, selenium has many and vital life supporting benefits. The main ones are:

  • Cardiovascular system support. The antioxidant effects of the mineral helps to keep the system free of fatty plaques that promote sluggish blood circulation and eventually vascular and heart disease
  • Brain functions support. Antioxidants have been shown to prevent brain cells damage and may prevent cognitive decline that comes with age.
  • Thyroid functions support
  • Cancer prevention. Selenium helps to protect the DNA. This in effect helps the cell to reach their ideal biological age (apoptosis). Some studies have suggested that low selenium levels increase risk of prostate cancer.
  • Supports normal pregnancy and fetal development
  • Promotes a healthy skin and hair
  • Supports healthy sexuality and reproductive health

People of different ages require different selenium dosage. Those going through physiological changes such as the expectant or nursing mothers also require amounts relevant to their conditions. The dosages below are pegged on estimated average requirements that will offer optimum antioxidant enzyme effects in plasma.

Individual                               Males µgm/day                    Females µgm/day                     Tolerable upper limit (µg)
Neonates 0-6 months           15                                            15                                                  45
07-12 months                          20                                           20                                                 60
1-3yrs                                         20                                           20                                                 90
4- 8 years                                 30                                           30                                                 150
9-13 years                                 40                                           40                                                 280
14 – 18 years                             55                                           55                                                 400
Over 19 years                           55                                           55                                                 400
Expectant mothers                                                               60                                                 400
Nursing mothers                                                                   70                                                 400

Selenium over dosage

Consumption of too much selenium over a prolonged period of time is harmful to health. It is unlikely to have selenium toxicity from the diet. However, Brazil nuts are known to have very high amounts of the mineral and continued and regular consumption of the nuts could lead to toxicity. Nutritional supplements containing high doses of selenium can also be a source of over-dosage and toxicity. Selenosis is the technical term for selenium toxicity. Symptoms of toxicity include:

  • Neurological disorders
  • Digestive problems
  • Skin lesions
  • Respiratory issues
  • Heart problems
  • Kidney failure

It is important to note the amount of selenium in any supplement product you buy. Make sure that it does not go beyond the recommended daily allowance. If it does, it should not be beyond the upper intake limit for your age and circumstance. An example of a well-formulated multivitamin-multi-mineral dietary supplement is Essential from Belisan. In this vegan supplement, selenium is only 25mcg which is about a half of the recommended daily allowance for an adult. There is no likelihood of toxicity when using this product.


Selenium can interact with a few drugs. These include

  • Some anti-seizure medications
  • Some antibiotics
  • Some chemotherapy drugs

If you have a medical condition or are on medications, it is advisable to consult your doctor before using selenium supplements.

For more details on how you can get a good multivitamin-multi-mineral product containing the organic form of selenium, click here.


Moslemi, M. K., & Tavanbakhsh, S. (2011). Selenium–vitamin E supplementation in infertile men: effects on semen parameters and pregnancy rate. International Journal of General Medicine, 4, 99–104.

“7 Selenium.” Institute of Medicine. 2000. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: The National Academies Press. doi: 10.17226/9810.

Flores-Mateo, G., Navas-Acien, A., Pastor-Barriuso, R., & Guallar, E. (2006). Selenium and coronary heart disease: a meta-analysis. The American Journal of Clinical Nutrition, 84(4), 762–773.

Berr, C., Balansard, B., Arnaud, J., Roussel, A.-M., Alpérovitch, A. and EVA Study Group (2000), Cognitive Decline Is Associated with Systemic Oxidative Stress: The EVA Study. Journal of the American Geriatrics Society, 48: 1285–1291. doi:10.1111/j.1532-5415.2000.tb02603.x

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