MineralNo.020
Selenium
Thyroid function, antioxidant defense.
Typical / RDA55 mcg
Upper limit400 mcg
EvidenceModerate
How to take it
Timing With a mealFood OptionalForm Selenomethionine
What to know
Just 1–2 Brazil nuts can supply a full day. The window is narrow and excess causes hair loss, brittle nails, and nerve issues — easy to overdo.
Interactions & cautions
- Toxicity from over-supplementation is real — respect the 400 mcg ceiling.
Do you actually need it?
A couple of Brazil nuts usually covers it.
Questions people ask about selenium
- Can You Take Iodine and Selenium Together? Absorption and SafetyYes, iodine and selenium are safe and often beneficial to take together for thyroid health. They work synergistically, with selenium protecting the thyroid during iodine metabolism.
- Selenium and Copper: Interaction, Absorption, and SafetySelenium and copper are generally safe to take together. The key interaction to watch is how high-dose zinc can deplete copper, not a direct selenium-copper conflict.
- Which supplements actually help with hair thinning and breakage?For hair thinning and breakage, biotin, collagen, zinc, and selenium are often marketed. Only zinc and selenium have moderate evidence, mainly for deficiencies.
- How much selenium is too much per day? What's the safe upper limit?The safe upper limit for selenium is 400 mcg per day. Exceeding this can lead to toxicity symptoms like hair loss and brittle nails.
Reference values: NIH Office of Dietary Supplements, adult general population. Educational information only — not medical advice. Confirm with a healthcare professional.