What type of food contain selenium?

A very interesting and great question, Jay
As a nurse, I would more consider what foods are not so high in Selenium.
Selenium, although advertised as a "supplement" and "anti-oxidant, is actually a mineral, just as Iron or lead.
It is found widely distributed in nature, the soil, and used in livestock feed and INSECTICIDES.
It is present, in adequate quantities, in soil, save some regions of the upper mid west, where sheep and livestock need to be injected if left to feed soly on native pasture and grasses.
This is , however the exception. The EPA has even set limits in water content (50 parts per million) and one commonly occurring form (selenium sulfate) is extremely toxic. The resulting disease is known as Selenism (brittle hair, nails, respiratory problems) It has even been linked to cancer but is not listed as a "Carcinogen".
In health care, selenium supplements are rarely used and usually when massive healing has to be promoted (burns, crushing injuries).
It is not truely, an "anti-oxidant" but is needed in an enzymes process in the formation of protien (i.e. healing). It is a mineral, pure and simple.
It is even possible, based on where you live, that you may have a high exposure to it (coal dust is the worst.)
A balanced diet with an normal amount of green vegitables and some red meat, should service you well.
If you do have a large need in tissue healing or protien formation, the E.P.A.(Environmental Polution Agency)recommends no more than 0.5 mg/kilogram/day.
I hope that this gives you enough information to decide if you need more than normal amounts.
You can check with your County Health or Agriculture Agency and check if you live in an area with low amounts in the soil but then, most of what we eat in grown in close proximinty to where we live.
Be Well

The richest food is brazil nuts!