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If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.
Selenium sounds like a made-up word to describe people’s obsession with Selena Gomez. But even if you think we might need a word for that, we need selenium more.
Selenium is an essential mineral involved in many bodily processes. Since we cannot make this trace element ourselves, we need to get enough through diet or supplements.
Many of its health benefits are brought about by proteins containing selenium, called selenoproteins; including one called glutathione peroxidase. But, just like fandom, too much of this good thing can be dangerous (Labunskyy, 2014).
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Selenium plays an important role in our endocrine, immune, and cardiovascular systems. Selenium is also found in high concentrations in the thyroid gland, which is responsible for keeping our metabolism humming. In fact, the enzymes that convert thyroid hormones are dependent on selenium (Shreenath, 2019).
Selenium is even involved in DNA synthesis. If that isn’t enough to convince you it’s worthy of having its own fan group, selenium is also crucial for reproduction and protects against infection.
Adults don’t need a lot of selenium, but we do need some in order to keep major systems in our bodies functioning the way they should. The recommended daily allowance (RDA) for adults over the age of 14 need 55 micrograms (mcg) daily, though this number jumps to 60 mcg for pregnant women and 70 mcg for breastfeeding women (Office of Dietary Supplements, 2019).
What is a selenium deficiency?
Selenium status differs greatly from one region to another. That’s because the selenium content of our food is determined by how much of this mineral was in the soil in which it grew.
Some areas of the United States have more selenium-rich soil than others, but Europe tends to have lower selenium levels than America. Low soil selenium, and therefore a higher chance of deficiency, is more common in Eastern Europe, China, and New Zealand (Shreenath, 2019).
In the case of New Zealand, this changed after the country started importing high-selenium wheat. Finland took a similar approach and started adding selenium to its fertilizer. This lack of selenium in the soil can even affect livestock. Sheep, goats, and cattle who eat a diet with selenium and vitamin E deficiency may develop a condition called white muscle disease in which the muscles degenerate from oxidative damage.
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Worldwide, between 500 million and 1 billion people have a selenium deficiency. In the United States and Canada, selenium deficiency is very rare, but there are groups of people who are at a higher risk.
People undergoing dialysis have a greater chance of developing a deficiency, as well as those living with HIV. Gastrointestinal conditions such as Crohn’s disease and celiac disease may also make it harder for people to absorb the selenium they need.
Selenium deficiency symptoms
So what does a selenium-deficient individual experience? If you’re not getting enough of the trace mineral, here are some of the signs you may encounter.
Everyone is different, however, and it’s important to note that you may be deficient and only experience some of these symptoms. Additionally, selenium deficiency on its own typically does not cause symptoms or illness.
For any of the below to occur, additional stresses (such as additional nutritional deficiencies) are usually also present.
This nonspecific symptom is, unfortunately, quite common with a number of mineral deficiencies. It’s frequently reported with selenium deficiency, too, and may have to do with the role this mineral plays in your normal thyroid function.
2. Foggy mental state
Mental fog can happen if your selenium intake dips low enough to cause deficiency. This symptom is also nonspecific but may help your healthcare provider diagnose you when considered in combination with other symptoms.
One study did find that low selenium levels were associated with poorer function on cognitive tests by older adults, though the researchers say that more research is needed (Shahar, 2010).
3. Weakened immune system
Low levels of selenium may make you more susceptible to infectious diseases or even turn other harmless pathogens into life-threatening illnesses.
Researchers believe this happened in the cases of Keshan disease, which gained attention after affecting a region of China where the soil was particularly deficient in selenium. This disease is caused by selenium deficiency combined with infection with coxsackievirus (the virus responsible for hand, foot, and mouth disease).
Research revealed that selenium deficiency amplifies the virus’s ability to cause cardiotoxicity, a condition in which there’s damage to the heart muscle that can compromise blood flow (Levander, 2000).
4. Hair loss
Thyroid hormones play an important role in hair growth and regeneration. Without selenium, the production of thyroid hormone is slowed. The cells in hair follicles respond to this drop in thyroid hormone, and your hair may fall out faster than usual (Ventura, 2017).
5. Muscle weakness
When we think of muscles, we think of our skeletal muscles specifically and forget about our cardiac muscles. Skeletal muscle disorders that cause weakness, pain, and fatigue have been reported in patients with low selenium levels (Chariot, 2003).
But selenium deficiency is also known to affect the heart muscles, as it does in the case of Keshan disease. Muscle weakness can also happen with patients receiving parenteral nutrition (when they’re “fed” nutrition through an IV, bypassing the digestive system entirely) because liquid nutrition tends to be low in this micronutrient.
Deficiencies in this micronutrient can not only cause issues with infertility but also problems during gestation if a woman is able to get pregnant.
There’s a correlation between selenium levels and fertility, but low levels in the early stages of pregnancy are also associated with miscarriage, low birth weight, and damage to the immune and nervous systems of the fetus (Pieczyńska, 2015).
Diagnosing a selenium deficiency
Diagnosing selenium deficiency can be done with a blood test, which indicated recent selenium intake. Hair or nail samples can also be taken which gives a better indication of long-term selenium status. Another test your healthcare professional may do is test your levels of glutathione peroxidase or other selenoproteins that require selenium to function.
Treating a selenium deficiency
Correcting low selenium requires increased dietary intake, selenium supplementation, or a combination of the two. Selenium supplements, generally made from sodium selenite or l-selenomethionine may be used by healthcare professionals if the deficiency is severe. Otherwise, taking a multivitamin or adding food sources of dietary selenium may be enough to get serum selenium to a healthy level.
Plant sources of selenium have selenomethionine, a form of selenium that’s 90% bioavailable. Meat, seafood, and dairy products are all good sources, though vegans may struggle to meet dietary reference intakes through food alone.
Once selenium levels are back into a healthy range, one Brazil nut (the most potent food source of this trace mineral) several times a week may be enough to keep them steady (Sheenath, 2019).
But you should always talk to a health professional who can assess your individual needs. It’s even more important for some people to have healthy levels of selenium and, potentially, to correct deficiencies faster. That includes people with thyroid nodules, thyroid conditions like Graves disease, weakened immune systems, or cancer.
Once your healthcare provider gives suggestions on dosage and supplementation, follow the medical advice you’re given. It’s important to keep in mind that the range of optimal daily intake for selenium is narrower than for other minerals.
While supplementation may be beneficial for those who have a low intake, supplementation could cause issues in those who have a normal or high intake. Selenosis, or selenium toxicity, is dangerous and can cause side effects such as hair loss, fatigue, nausea, and vomiting.
- Chariot, P., & Bignani, O. (2003). Skeletal muscle disorders associated with selenium deficiency in humans. Muscle & Nerve, 27(6), 662–668. doi: 10.1002/mus.10304, https://onlinelibrary.wiley.com/doi/abs/10.1002/mus.10304
- Contreras-Jurado, C., Lorz, C., García-Serrano, L., Paramio, J. M., & Aranda, A. (2015). Thyroid hormone signaling controls hair follicle stem cell function. Molecular Biology of the Cell, 26(7), 1263–1272. doi: 10.1091/mbc.e14-07-1251, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4454174/
- Labunskyy, V. M., Hatfield, D. L., & Gladyshev, V. N. (2014). Selenoproteins: Molecular Pathways and Physiological Roles. Physiological Reviews, 94(3), 739–777. doi: 10.1152/physrev.00039.2013, https://www.ncbi.nlm.nih.gov/pubmed/24987004
- Levander, O. A. (2000). The Selenium-Coxsackievirus Connection: Chronicle of a Collaboration. The Journal of Nutrition, 130(2). doi: 10.1093/jn/130.2.485s, https://academic.oup.com/jn/article/130/2/485S/4686512
- Office of Dietary Supplements – Selenium. (n.d.). Retrieved December 18, 2019, from https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/.
- Pieczyńska, J., & Grajeta, H. (2015). The role of selenium in human conception and pregnancy. Journal of Trace Elements in Medicine and Biology, 29, 31–38. doi: 10.1016/j.jtemb.2014.07.003, https://www.ncbi.nlm.nih.gov/pubmed/25175508
- Shahar, A., Patel, K. V., Semba, R. D., Bandinelli, S., Shahar, D. R., Ferrucci, L., & Guralnik, J. M. (2010). Plasma selenium is positively related to performance in neurological tasks assessing coordination and motor speed. Movement Disorders, 25(12), 1909–1915. doi: 10.1002/mds.23218, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3270688/
- Shreenath, A. P., & Dooley, J. (2019). Selenium Deficiency. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK482260/
- Ventura, M., Melo, M., & Carrilho, F. (2017). Selenium and Thyroid Disease: From Pathophysiology to Treatment. International Journal of Endocrinology, 2017, 1–9. doi: 10.1155/2017/1297658, https://www.ncbi.nlm.nih.gov/pubmed/28255299