More than sun and skin: Investigating the social and developmental determinants of vitamin D production

Perez, Julianna

doi:https://doi.org/10.21985/n2-pd62-p697

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More than sun and skin: Investigating the social and developmental determinants of vitamin D production

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Recent discoveries in vitamin D research indicate that vitamin D is a necessary component to several organs and tissues that extends beyond bone formation Furthermore, recent research indicates that vitamin D deficiency is rampant across the globe. Historically, anthropological research has focused on the adaptive significance of skin color to minimize the harmful effects of exposure to ultraviolet rays while maintaining vitamin D production. While foundational in biological anthropology, unanswered questions remain regarding the developmental and environmental factors that shape vitamin D production within populations, in a single generation. For example, within populations, gender, season of birth, time spent outdoors, urbanicity and socioeconomic factors all contribute to variation in patterns of sun exposure, and therefore levels of vitamin D. Therefore, the objective of this dissertation is to advance a biocultural anthropological understanding of vitamin D by exploring the more proximate environmental factors that explain vitamin D variation through the life course. Data from the Philippines, a tropical country, was used to assess the impact of vitamin D among people in the Cebu Longitudinal Health and Nutrition Survey in the Philippines. Vitamin D assays were performed from whole blood samples from a sample of 349 young adults ages 20-22 years (66 males, 283 females) to determine circulating vitamin D levels. Socio-cultural environmental factors in both childhood and adulthood were analyzed to determine the impact of those variables on vitamin D levels in adulthood. Vitamin D status was then analyzed in conjunction with already existing DNA methylation data from the same participant samples. DNA methylation was evaluated as a predictor of the vitamin D receptor gene (VDR) and four vitamin D metabolism enzyme genes (CYP2R1, CYP24A1, CYP27A1, CYP27B1). DNA methylation is a mechanism through which environments during development can regulate genome activity through the addition of methyl groups to CpG dinucleotides. Combining ecosocial and epigenetic analyses, this project sought to understand what factors in early life and adulthood affect vitamin D variation for the entire sample and between females and males. This project also investigated whether DNA methylation provided a mechanism through which childhood environments can regulate genome activity resulting in vitamin D variation. DNA methylation of genes in the vitamin D metabolic process was found to not be predictive of circulating vitamin D levels. However, environmental factors in childhood and adulthood were found to be predictive of vitamin D with sex strongly predicting vitamin D levels.

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