The majority of the selenium in eggs is located in the yolk.
According to the USDA National Nutrient Database, an egg white from a large egg provides 6.7 micrograms of selenium, whereas the entire egg provides 15.9 micrograms!
The USDA's SR.21 Report indicates that 1 cup of flax seeds contain 42.7 mcg of selenium.
According to this study, flax seeds have the highest content of pre-cursors for lignans (a cancer-fighting compound) that work with your gut's good bacteria to create complete lignans- it's kinda a team effort. The gut flora in your intestines (or good bacteria) is responsible for detoxifying or activating varying compounds that are ultimately made available to your body! That's really working from the inside out ;)
According to the USDA National Nutrient Database, salmon has 25-30 ug of selenium per every 3 ounces.
The EPA and FDA recognize salmon as a low-mercury fish and recommend consuming no more than 12 ounces of low-mercury fish a week.