What is Selenium?
Selenium is a mineral found in the earth, and it gets passed into your food by means of the particular soils or waters that plants or animals consume. As a result, you’ll find it in all sorts of different foods, including fish, cereals, pasta, and, especially, brazil nuts.
However, as it’s a chemical element, its richness in certain foods will depend on where in the world they’re produced. In some areas of rural China, for example, people have historically suffered from selenium deficiency as a result of the low quantities of the mineral in the local soil. The same is true of New Zealand, where efforts were made to import selenium-rich grains.
And according to a 2001 paper by the British Nutrition Foundation, selenium intake has dropped hugely over the last decades in the UK. This has reached the point which, at publication, selenium consumption was almost only half of the recommended daily amount.
What are the Health Benefits of Selenium?
At the same time, though, selenium has become increasingly popular in the world of dietary supplements — particularly among those seeking the many health benefits that have been attributed to it.
While selenium plays an important role in many of the body’s processes, scientific studies have not found conclusive evidence that boosting your intake necessarily improves your health.
Let’s take a look at some of the most important findings and see where selenium can really have a benefit:
Selenium May Reduce the Risk of Cancer
There’s a lot of volume surrounding the role that selenium might play in reducing the risk of cancer. Yet, while such a link between the disease and the mineral would be exciting, the evidence is not definitive.
According to one 2016 study — which included 69 prior studies, involving over 300,000 people — a link was found between the amount of selenium in your bloodstream and your risk of cancer. The results suggested that the more selenium in your blood, the lower the chance of lung, breast, or prostate cancer. Interestingly, however, no benefit was found by taking selenium supplements.
Other studies have shown similarly mixed results. A review of selenium’s effect on prostate cancer risk showed that while one study found positive results, two others did not. A 2008 paper, meanwhile, concluded that there is still insufficient evidence to associate selenium with cancer risk.
It May Improve Cardiovascular Health
One of selenium’s benefits is thought to be a prevention of cardiovascular disease. One of the most notable conditions caused by a selenium deficiency is the heart disease known as Keshan disease — however, as with other heart diseases, the jury is still out.
Something that looked positive was an overview of 25 different studies which found that, on average, a 50% increase in selenium concentration in the blood led to a 24% decrease in the risk of coronary heart disease. However, none of these studied the effect of selenium supplements.
Research continues to observe that further studies into the role of selenium supplements are needed. But it does look hopeful that selenium may benefit your cardiovascular health.
It Could Help Cognitive Decline
Research has shown that people with Alzheimer’s have lower levels of selenium in their blood. However, this does not necessarily show that increasing selenium brings benefits to your cognitive capacities.
Investigating exactly this, a 2011 study involving over 4000 people found that people who took mineral supplements (including selenium) increased their verbal memory and executive functioning. Whether this improvement was selenium’s benefit alone or one of the other minerals included, is unclear.
Selenium Improves the Health of Your Hair
Selenium is recognised by scientists to be important in the development of proteins crucial for the growth of healthy hair. Studies have revealed its role in hair pigmentation and in hair growth, while rats with selenium deficiency have been found to have sparse and unhealthy hair.
While this might be great news for men suffering from male pattern baldness, what’s important to note is that too much of the mineral can result in the reversal of selenium’s benefits. This applies particularly to the hair: excessive selenium consumption can result in hair loss.
How Much Selenium Do You Need Daily?
As we noted above, in the UK, the average consumption of selenium was dramatically below the recommended daily intake. But how much do you actually need to feel selenium’s benefits?
While that depends on your age, according to the NHS the recommended amount of selenium to be consumed a day by men is 0.075mg, or 75 micrograms (µg). For women, that number is 60µg. That’s your minimum, but it’s estimated that on average in the UK, people only receive 39µg a day.
According to the US government, adults should not consume over 400µg of selenium in a day. This is because, in too high quantities, selenium can be toxic and can lead to a condition known as selenosis. This can cause damage to the hair and nails and can lead to symptoms including diarrhoea, nausea, and fatigue. For those of you considering selenium supplements, ensuring that you stay within recommended dosages is crucial.
Generally speaking, most people can achieve the recommended levels of selenium by maintaining a balanced diet. Brazil nuts, for example, include very high quantities of selenium — as much as 48µg per nut, according to New Zealand’s nutritional agency. One poached egg contains 21µg of selenium, while 100g of tuna contains 47µg. This shows that there are many food sources that provide you with ample quantities of your required minerals.
Key Takeaways
Selenium’s health benefits, like those of all minerals and vitamins, come from having the right amounts. Too little and you can experience deficiencies; too much and it can be toxic.
75µg of selenium a day is the recommended amount in the UK, and that can be quite easily consumed in your diet without the need for supplements.
¹Junshi Chen (2012). An original discovery: selenium deficiency and Keshan disease (an endemic heart disease): https://www.ncbi.nlm.nih.gov/pubmed/22705420?dopt=Abstract
²Medsafe – Selenium: https://www.medsafe.govt.nz/profs/puarticles/sel.htm
³The British Nutrition Foundation – Selenium and Health: https://www.nutrition.org.uk/attachments/145_Selenium%20and%20health.pdf
⁴Xianlei Cai, Chen Wang, Wanqi Yu, Wenjie Fan, Shan Wang, Ning Shen, Pengcheng Wu, Xiuyang Li and Fudi Wang (2016). Selenium Exposure and Cancer Risk: an Updated Meta-analysis and Meta-regression: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4726178/
⁵Lei Yang, Mouracade Pascal, Xiao-Hou Wu (2013). Review of selenium and prostate cancer prevention: https://www.ncbi.nlm.nih.gov/pubmed/23725109
⁶Ujang Tinggi (2008). Selenium: its role as antioxidant in human health: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2698273/
⁷Gemma Flores-Mateo, Ana Navas-Acien, Roberto Pastor-Barriuso, and Eliseo Guallar (2007). Selenium and coronary heart disease: a meta-analysis: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1829306/
⁸Zuzanna Sabina Goluch-Koniuszy (2008). Nutrition of women with hair loss problem during the period of menopause: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4828511/
⁹Hind M. Almohanna, Azhar A. Ahmed, John P. Tsatalis, and Antonella Tosti (2018). The Role of Vitamins and Minerals in Hair Loss: A Review: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6380979/
¹⁰J M Bates, V L Spate, J S Morris, D L St Germain, V A Galton (2000). Effects of selenium deficiency on tissue selenium content, deiodinase activity, and thyroid hormone economy in the rat during development: https://www.ncbi.nlm.nih.gov/pubmed/10875250
¹¹NHS – Vitamins and minerals: https://www.nhs.uk/conditions/vitamins-and-minerals/others/
¹²National Institutes of Health (NIH) – Selenium: https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/
¹³Nutrition Foundation – Selenium: https://nutritionfoundation.org.nz/nutrition-facts/minerals/selenium
While we've ensured that everything you read on the Health Centre is medically reviewed and approved, information presented here is not intended to be a substitute for professional medical advice, diagnosis, or treatment. It should never be relied upon for specific medical advice. If you have any questions or concerns, please talk to your doctor.
