January 2019 in “Figshare” This study found that redhaired individuals exhibit higher calcidiol levels compared to non-redhaired individuals, suggesting a possible evolutionary adaptation for vitamin D photosynthesis in low UV-B environments in Europe.
January 2025 in “Digital Repository (National Repository of Grey Literature)” In this study, analysis of questionnaire data from over 111,000 respondents revealed that red hair is significantly associated with a higher level of mental health problems in both men and women, while red-haired women also exhibited poorer overall physical health.
December 2019 in “bioRxiv (Cold Spring Harbor Laboratory)” This study found that redhaired individuals consistently had higher calcidiol levels compared to non-redhaired subjects, suggesting a physiological adaptation for vitamin D synthesis in low UV-B conditions.
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June 2020 in “Experimental dermatology” This study found that redheaded individuals had higher levels of vitamin D precursor 25(OH)D3 compared to non-redheaded individuals, suggesting a physiological adaptation to low UVB radiation in Europe.