You probably know the heavy feeling of waking up tired after a full night's sleep. Most of us put it down to stress, a bad week, or just getting older. For some people, though, the body is quietly short on something more basic.
That something is selenium. According to NIH's clinical reference StatPearls, the body uses this trace mineral in two central ways.
It converts inactive thyroid hormone, called T4, into the active form, T3, that your cells actually run on. It also builds a family of proteins called selenoproteins that help the immune system do its job.
Severe deficiency is uncommon in the United States, where food distribution helps even out regional soil differences. But moderate shortfalls happen, and the early signs look like ordinary exhaustion.
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1. Persistent fatigue. The NIH Office of Dietary Supplements lists selenium deficiency as a possible contributor to hypothyroidism and a weakened immune system. Both quietly drain daily energy.
2. Thinning hair and brittle nails. Doctors assessing selenium status check the nails for white spots and brittleness. Hair and nail changes often track with the thyroid changes selenium can trigger.
3. Catching every bug. Selenoproteins protect immune cells from oxidative damage. StatPearls notes that selenium deficiency has even been observed to transform otherwise benign viruses into more virulent pathogens in the host.
4. Muscle weakness and aches. StatPearls says muscle wasting and weakness are commonly linked with moderate selenium deficiency.
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5. Trouble concentrating. Low selenium can affect the turnover of certain brain chemicals, and poor selenium status has been linked to foggy thinking and heightened confusion.
6. Low mood and anxiety. StatPearls reports that insufficient selenium has been associated with depressed mood, increased anxiety and hostile behavior.
7. Reduced male fertility. Selenium is essential for testosterone production and the healthy formation of sperm, which is why moderate deficiency is tied to increased male infertility.
8. Heart muscle problems in severe deficiency. The clearest extreme is Keshan disease, a congestive cardiomyopathy first described in a selenium-poor region of China. It brings an enlarged heart, heart failure and heart rhythm abnormalities.
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How much selenium adults actually need
The adult recommended intake is 55 micrograms a day, with 60 micrograms in pregnancy and 70 during breastfeeding. The gap between enough and too much is narrow. The tolerable upper intake level is 400 micrograms a day.
Too much selenium causes a condition called selenosis. According to the NIH Office of Dietary Supplements, the signs include gastrointestinal upset, hair loss, white blotchy nails, a garlic breath odor, fatigue, irritability and mild nerve damage.
Where to get selenium in food
Food is almost always a better route than pills. The NIH ODS lists these as reliable sources.
Food Also read: How eating blueberries every day may protect your memory and sharpen your focus | Serving | Selenium (mcg) |
|---|---|---|
Brazil nuts, dried | 1 ounce (about 6 nuts) Also read: Raw oysters sold at Publix recalled in 15 states and DC over Salmonella outbreak | 544 |
Tuna, light, canned in oil | 3 ounces | 63 |
Cod, cooked | 3 ounces | 32 |
Chicken breast, roasted | 3.5 ounces | 20 |
Egg, whole | 1 medium | 14 |
A single Brazil nut can already cover an adult's daily need, which is why health authorities advise sticking to one or two a day rather than eating them by the handful.
If you suspect low selenium or have symptoms that will not shift, talk to your doctor instead of reaching for a high-dose pill. Selenium has a narrow therapeutic window and should not be self-dosed above around 200 micrograms without medical supervision.
A simple serum selenium blood test can confirm the question, with the Institute of Medicine's reference range running 70 to 155 micrograms per liter.
This article is made and published by Mie Hermansen, who may have used AI in the preparation.