The Study
Associations between food group intake and serum levels of selenium and other essential and toxic trace elements in adults
This study looked at what people ate and measured how much selenium was in their blood. It found that people who ate more fish tended to have more selenium, but it didn't prove that eating fish made their selenium go up — maybe people with more selenium just liked eating fish more. So it's like noticing that people who wear raincoats often have wet shoes — but we don't know if the raincoat caused the wet shoes or if both happened because it rained.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
This study looked at what people in Spain ate and checked their blood for selenium and other tiny elements. It found that fish raises selenium (good) but also arsenic and mercury (bad). Dairy helps with many minerals, but oil and bread might block selenium absorption.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 544 / 100
Quality score
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — eating 4 fish servings a week can help meet selenium needs, but it also increases exposure to toxic metals, so balance matters.
- 2People with enough selenium ate about 4 fish servings a week.
- 3Eating more oil lowered selenium by 5.3% per unit, and more grains lowered it by 0.8% per unit.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
European Journal of Nutrition
Year
2026
Authors
Inés Rivas, Marta Miranda, C. Herrero-Latorre, Rafael Monte-Secades, M. López-Alonso
Related Content
Claims (7)
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 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.
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.
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.
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 dairy products is consistently linked to higher or lower levels of 13 out of 14 trace minerals in the blood, suggesting dairy may affect how these minerals are absorbed or balanced in the body.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.