FIGURE 1.

Concentration of serum 25(OH)D₃ by RBC log₁₀(δ¹⁵N value) in adult Alaska Native (Yup’ik) people [n = 689 participants with data for both serum 25(OH)D₃ concentration and RBC log₁₀(δ¹⁵N value). Least-squares linear regression, with goodness of fit indicated by the R² regression coefficient, was used. The P value, as calculated by a likelihood ratio test, was <0.0001. The δ¹⁵N value represents a biomarker of traditional food intake as defined in Methods. 25(OH)D₃, 25-hydroxycholecalciferol.