Table 1.
Summary of Selenium Biomarkers.
| Component of Se Status | Specimen | Se Biomarker | Informative Value | Limitations |
|---|---|---|---|---|
| Se Intake | foods | Se form and amount; amount of food consumed | Approximates total Se consumed. | Use of food nutrient data bases do not address regional variation or digestibility. |
| Tissue Se | Humans: whole blood, plasma/serum; erythrocytes, buccal cells, lymphocytes, nails, hair; Animals: also liver, muscle, other tissues | total Se | Indicates portion of ingested Se absorbed and retained. Most useful in animal studies in which larger body Se pools (liver, muscle) can be sampled. | nail, hair: Samples represent past Se status; collection must be standardized; samples subject to contamination |
| non-specific protein-SeMet | Indicates portion of retained Se that may become available for functional purposes over medium-long term. | Must be imputed from Se and selenoprotein contents of tissues. Can be approximated by albumin-Se (few supporting data). | ||
| Se Function | Humans: whole blood, plasma/serum; erythrocytes, buccal cells, lymphocytes; Animals: also liver, muscle, other tissues | nutritional: selenoproteins | Indicates Se function, portion of retained Se in functional forms. In humans, GPX3, GPX1 and SEPP1 are most useful—can be measured in plasma, and blood/buccal cells. | Assays established for GPX’s, SEPP1, TXNRDs and DIOs. |
| antitumor: Se-metabolites, e.g., CH3SeH | (Would indicate amount of Se antitumorigenically active.) * | CH3SeH has not been detected in tissues. | ||
| adverse effects: Se-metabolites, e.g., (CH3)xSe | (Would indicate Se function and portion of retained Se in functional forms.) * | Methylated Se-metabolites have not been detected in tissues. | ||
| Se Excretion | urine | total Se | Indicates major portion of absorbed Se not retained. | |
| Se-sugar | Major form of excreted Se in humans. | Minor component of excreted Se in animals (rodents). | ||
| (CH3)3Se+ | Major form of excreted Se in animals (rodents). | Minor component of excreted Se in humans. | ||
| feces | total Se | Indicates amount of Se available to the hindgut microbiome. | Does not inform re functional effects on the microbiome. | |
| breath | (CH3)2Se | (Would indicate exposure to potentially intoxicating levels of Se.) * | Diagnostic criteria of selenosis not established. Confounders: low methyl status, folate, vit. B12; methylmercury exposure. |
* Methodology not currently available.