Early lifecycle UV-exposure calibrates adult vitamin D metabolism: evidence for a developmentally originated vitamin D homeostat that may alter related adult phenotypes

Objectives: Within the Developmental Origins of Adult Disease (DOHaD) model, early life environmental exposures can confer a long‐term legacy on human health. This mechanism may be adaptive or maladaptive depending on lifestyle circumstances. This article examines the role of first trimester UV‐exposure on late‐life vitamin D levels, and potentially related adaptive and maladaptive phenotypes (height and osteoporosis respectively). Methods: Six hundred and forty nine subjects were examined for vitamin D₂ and D₃ (HPLC) and height (stadiometer). Osteoporosis was assessed with an extensive medical history questionnaire. Results: Solar irradiance over the first 90 days postconception correlated positively with late‐life vitamin D₃ (R² = .0140; P = .0082; β = .1075), but not vitamin D₂ levels. It also correlated positively with female adult height (R² = .170; P = .0103; β = .1291) and negatively with the occurrence of female osteoporosis (P = .0495). All data were adjusted for age and gender as appropriate (unadjusted data also provided). From a contemporary perspective, vitamin D levels varied significantly according to season of blood sampling as might be predicted (P = .0009). Conclusions: Increased solar irradiance/UV exposure during the first trimester of pregnancy calibrates adult vitamin D metabolism, which is an important hormone in maintaining calcium balance. This may explain how very early lifecycle UV exposure can influence skeletal development (adult height) and modify risk for the skeletal degenerative disorder osteoporosis. The data demonstrate humans are tuned to the world (exposome) in ways we have not yet fully considered, and which are entrained at the earliest phase of the lifecycle.