Data for the article "Increased calcidiol level in redhaired people: Could redheadedness be an adaptation to temperate climate?"

About 1–2% of European
population are redhaired, meaning they synthesize pheomelanin instead of eumelanin,
the main melanin pigment. Several mutations could be responsible for this
phenotype. It has been suggested that corresponding mutations spread in Europe due
to a founder effect shaped either by a relaxation of selection for dark, UV-protective
phenotypes or by sexual selection in favor of rare phenotypes. In our study, we
investigated the levels of vitamin D precursor calcidiol and folic acid in the
blood serum of 73 redhaired and 130 non-redhaired individuals. In redhaired
individuals, we found higher calcidiol concentrations and approximately the same
folic acid concentrations as in non-redhaired subjects. Calcidiol concentrations
correlated with the intensity of hair redness measured by two spectrophotometric
methods and estimated by participants themselves and by independent observers. In
non-redhaired individuals, calcidiol levels covaried with the amount of sun exposure
and intensity of suntan while in redhaired individuals, this was not the case. It
suggests that increased calcidiol levels in redhaired individuals are due to
differences in physiology rather than in behavior. We also found that folic
acid levels increased with age and the intensity of baldness and decreased with
the frequency of visiting tanning salons. Our results suggest that the redhaired
phenotype could be an evolutionary adaptation for sufficient photosynthesis of
vitamin D in conditions of low intensity of UV-B radiation in central and
northern parts of Europe.