As he points out, it is nearly impossible for any one of us to know how much selenium we consume, so it may be time for the government to consider fortifying certain foods. Fish is an excellent source of selenium, so eat two or three servings weekly. Meats and poultry are good sources, but limit yourself to small portions and lean cuts. Make whole grains part of your daily fare. Whole grains contain selenium, as well as fiber, vitamins, and other minerals.
Brazil nuts are a great source.
Other nuts have small amounts. Nuts, despite the many good things they contain, are very high in fat and calories, so stick to small portions. We don't recommend separate selenium supplements. If you do take them, don't go over 200 micrograms a day. Multivitamins offer anywhere from 20 to 200 micrograms.