What selenium does
Selenium is built into selenoproteins — antioxidant enzymes that protect cells from damage — and helps the thyroid activate its hormones.
How much
Adults need about 55–70 µg a day. The safe upper limit is 255 µg a day in the EU (400 µg in the US), so more isn’t better.
Plant sources
How much selenium plants contain depends on the soil. Brazil nuts are by far the richest source; whole grains, couscous, oats, mushrooms and sunflower seeds add smaller amounts.
How many portions of each food would cover a day's selenium?
Tips
One or two Brazil nuts a day is the easiest way to cover your needs (One Brazil nut a day).