Selenium is a trace mineral that our body cannot do without. It is present in most body tissues, with the highest concentration at internal organs and glands such as kidney, liver, spleen, pancreas, heart, brain thyroid, and lungs [1]. Selenium presents in the body in the form of a class of proteins called selenoprotiens. Many of the selenoprotiens are important enzymes for body functions and health. Among them include the Glutathione peroxidase family, which biological role is to protect the cells from oxidative damage, as well as Iodothyronine deiodinase which is required in the production of thyroid hormone [2]. Hence, our body needs selenium to function properly.

What is selenium good for?

Research has found that a low level of selenium in the body can have detrimental effects on health and is associated with the risk of many diseases and even death. Here is a summary of the health impact of selenium based on the latest scientific evidence [2]:

• High selenium status is associated with lower risk of mortality in at least 3 large cohort studies including those conducted in USA, UK, and France, especially among the elderly.
• For immune compromised people, such as HIV or cancer patients and elderly, selenium is an immune stimulant that can protect against viral infection and other risks due to weakening immunity.
• Selenium is also a neuroprotector, depletion of selenium is linked to cognitive decline, Parkinson’s disease, seizures, and loss of coordination.
• Fertility in both male and female is linked to selenium. It is essential for sperm motility and normal gestation of the foetus. Low selenium status in pregnancy is linked to pregnancy complications and recurrent of miscarriages.
• Thyroid glands have a high concentration of selenium, lower selenium level is associated with thyroid hormonal imbalance, such as Hashimoto’s thyroiditis and Graves’ disease. Supplementation of selenium has been shown to be effective in these conditions.
• Selenium is helpful for cardiovascular health. It can prevent oxidation of cholesterols that can potentially lead to atherosclerosis. It can also inhibit platelet aggregation and reduce inflammation.
• Strong evidence suggests that higher selenium intake can be beneficial for cancer patients, especially for lung, bladder and prostate cancers.

What type of food has selenium?

Selenium is present, in both organic and inorganic form, in many types of food. Seafoods and organ meats are the riches food sources of selenium, follow by meat and poultry, bread and cereals, dairy products, as well as fruits and vegetables. Brazil nut has the highest concentration of selenium per serving (544µg/serving), more than 7 times the recommended daily intake of selenium for adults (70 µg/day) [3]. Hence, with the abundance of selenium food sources, it is not hard to ensure sufficient intake of selenium from food if one takes a properly balanced meal.

However, several factors can affect the availability of selenium in food and individual demand for this essential nutrient. Firstly, locality and environment affect the selenium content in the food due to the variability of selenium content in the soil and the availability of selenium to the food chain. Hence, studies around the world found different level of average selenium level in blood in population in different countries [2]. A study conducted in Singapore the 90s found the average selenium level of Singaporean population to be 122 µg/L which is lower that of European and American population [4]. Aging, alcohol, smoking, infection and disease, heavy metal contamination, etc. are all factors that can deplete the body’s selenium store and thus increase demand [5].

Should I take selenium supplement?

Even though selenium is crucial for health, it remains a toxic substance at high concentration. As such, one should not overdose with selenium in supplement form and is not recommended to take a high dose of selenium for long-term. The recommended upper limit of selenium intake is 400 μg/d. Selenium overdose can cause cell death and the symptoms include nausea; vomiting; nail discolouration, brittleness, and loss; hair loss; fatigue; irritability; and “garlic breath” [6].

Therefore, increase intake of selenium-rich food should be the preferred approach to replenish one’s selenium level. One simple way is to simply take 1-2 kernels of Brazil nut daily. Before taking any selenium supplement, it is best to take a blood test to determine your blood selenium level and consult a qualified health professional on your need for selenium supplement. Taking off-the-shelf selenium supplement may be unnecessary and may increase your risk of diabetes type 2 if you are already having a high level of selenium in the body [2]. The ideal range of selenium in the body is between to 130 to 150 μg/L according to research as this is the range that is associated with the lowest level of mortality according to population-based studies.

Conclusion

Selenium is an important trace element for the body. Maintaining a healthy range of selenium between 130 to 150 μg/L is important for our immune system, brain function, thyroid function, fertility, cardiovascular health, cancer and mortality risk. Selenium is available abundantly inSelenium and health the food of both animal- and plant-origin and thus selenium supplementation is not necessary should we keep to a healthy diet and lifestyle. Do not take selenium supplement unnecessarily.

References

[1]        B.A. Zachara, H. Pawluk, E. Bloch-boguslawska, K.M. Śliwka, J. Korenkiewicz, Ź. Skok, K. Ryć, Tissue Level, Distribution and Total Body Selenium Content in Healthy and Diseased Humans in Poland, Arch. Environ. Heal. An Int. J. 56 (2001) 461–466. doi:10.1080/00039890109604483.

[2]        M.P. Rayman, Selenium and human health, Lancet. 379 (2012) 1256–1268. doi:10.1016/S0140-6736(11)61452-9.

[3]        Selenium — Health Professional Fact Sheet, (n.d.). https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/ (accessed October 28, 2018).

[4]        K. Hughes, L.H. Chua, C.N. Ong, Serum selenium in the general population of Singapore, 1993 to 1995., Ann. Acad. Med. Singapore. 27 (1998) 520–3. http://www.ncbi.nlm.nih.gov/pubmed/9791658 (accessed October 28, 2018).

[5]        H. Osiecki, The Nutrient Bible, 9th Ed., BioConcepts Publishing, Eagle Farm, OLD, Australia, 2014.

[6]        J.K. MacFarquhar, D.L. Broussard, P. Melstrom, R. Hutchinson, A. Wolkin, C. Martin, R.F. Burk, J.R. Dunn, A.L. Green, R. Hammond, W. Schaffner, T.F. Jones, Acute selenium toxicity associated with a dietary supplement., Arch. Intern. Med. 170 (2010) 256–61. doi:10.1001/archinternmed.2009.495.