The hack
Selenium is a trace mineral you need only in tiny amounts — and Brazil nuts contain so much that one or two typically cover a day. That’s easier than trying to piece it together from other foods.
Do this
Keep a jar of Brazil nuts and eat one or two a day — on porridge or as a snack.
Don’t overdo it
More is not better. Selenium has a safe upper limit, and eating a handful of Brazil nuts every day can exceed it. If you take a multivitamin containing selenium, one nut a few times a week is enough.
See Selenium and Brazil Nuts.