Dietary selenium in humans toenails as an indicator

Area of Science:

• Nutritional Science
• Environmental Health
• Biomarker Research

Background:

• Growing evidence links selenium to cancer and heart disease etiology.
• Accurate biomarkers are needed to assess selenium exposure in populations.
• Previous studies have explored hair and nails as potential indicators.

Purpose of the Study:

• To evaluate toenails and hair as reliable indicators of selenium intake.
• To assess the utility of toenail selenium levels in epidemiologic research.
• To compare selenium levels across geographic areas with varying selenium intake.

Main Methods:

• Neutron activation analysis was used to measure selenium levels in hair, nails, and blood.
• Duplicate samples were analyzed for reproducibility.
• Selenium concentrations in toenails were compared between South Dakota (high selenium), Boston/Georgia (medium selenium), and New Zealand (low selenium).

Main Results:

• Toenail selenium levels were reproducible and varied significantly by geographic region, correlating with known selenium intake levels.
• Hair samples showed contamination from selenium-containing shampoos, rendering them unreliable.
• South Dakota toenails (1.17 ppm) had significantly higher selenium than Boston (0.74 ppm) and Georgia (0.81 ppm), while New Zealand (0.26 ppm) was distinctly lower.
• Familial aggregation of selenium levels in South Dakota suggested dietary influences.

Conclusions:

• Toenails serve as a reliable, long-term biomarker for selenium intake, unaffected by external contamination.
• Toenail selenium analysis is suitable for large-scale epidemiologic studies investigating selenium's role in chronic diseases.
• Hair is not recommended as a biomarker due to contamination risks.