In healthy adults from Galicia, Spain, the amount of selenium in the blood changes more noticeably with dietary intake than the levels of zinc, copper, or iron, which stay relatively constant due to biological regulation. This makes selenium a more reliable indicator of whether dietary intake is sufficient.

In healthy adults from Galicia, Spain, people who consume more dietary oil tend to have lower levels of selenium in their blood, which may be related to how fat in the diet affects selenium absorption or reflects broader dietary habits.

In healthy adults from Galicia, Spain, eating more grains is linked to slightly lower levels of selenium in the blood, possibly because compounds in grains interfere with selenium absorption.

People in Galicia, Spain, who eat more seafood tend to have higher levels of selenium in their blood, and those with sufficient selenium levels typically eat about four servings of fish per week.

In Brazil, people with lower income and non-white skin color tend to consume less selenium in their diet than those with higher income and white skin color, which may increase their risk of not getting enough of this essential nutrient.

People in Galicia, Spain, who eat more seafood have higher levels of selenium—a beneficial nutrient—as well as higher levels of toxic elements like arsenic and mercury in their blood, because seafood contains both.