Ralston et al. 2014 — Selenium health benefit value (HBVSe) for methylmercury risk assessment
This paper refines the selenium health benefit value (Se-HBV) to produce the improved HBVSe index, a biochemically based risk assessment criterion for concurrent evaluation of methylmercury (CH3Hg) and selenium (Se) in seafood. The original Se-HBV equation was prone to divide-by-zero errors at very low Hg concentrations; the modified HBVSe eliminates this by incorporating relative and absolute molar amounts of both Hg and Se. The index reflects the degree to which dietary Se is in excess of or deficient relative to CH3Hg, reflecting the molecular mechanism by which high CH3Hg exposures inhibit Se transport across the placenta and irreversibly inhibit fetal brain selenoenzymes. A positive HBVSe indicates net Se surplus (protective); a negative value indicates Se deficit (risk). The index supports FDA/EPA advice on seafood choices for pregnant and breastfeeding women.
Key numbers
Equation: HBVSe = ([Se - Hg] / Se) × (Se + Hg), where Se and Hg are in molar concentrations (µmol/kg). Positive values indicate Se surplus relative to Hg; negative values indicate Se deficit. Reference selenium content used in comparisons: ~10.0 µmol Se/kg (average in ocean fish). Range of CH3Hg in seafood comparison: 0.125 to 34.9 µmol Hg/kg (0.025 to 7.0 mg/kg). The paper confirms HBVSe supports the biochemical mechanism: high CH3Hg sequesters Se, inhibiting selenoenzymes critical for brain health and fetal development.
Methods (brief)
Mathematical derivation and comparative evaluation of Se-HBV vs HBVSe using published Se and CH3Hg concentrations across range of seafood types. No primary sample collection; theoretical comparison against published seafood data.
Implications
Certification: the HBVSe framework is relevant to fish/seafood certification where both Hg and Se are measured; a positive HBVSe for a seafood product provides an evidence-based counterargument to simple total-Hg exceedance concerns.
Courses: important mechanistic teaching case for the Se-Hg antagonism, why tHg:MeHg conversion is typically >75-95% in fish muscle, and why absolute MeHg concentrations must be considered alongside dietary Se.
App: for fish/seafood ingredient risk scoring, a species-specific HBVSe calculation (requiring species Se data alongside Hg data) could refine risk estimates beyond simple tHg thresholds.