The recent article by Brenner et al. reported that, compared to those born in summer, those born in winter had an increased risk of brain tumors as adults. Other studies have also reported an association between season of birth and childhood brain tumors.
We would like to propose a specific risk-modifying factor that may be causally related to these findings—low prenatal vitamin D3. Levels of vitamin D3 are known to fluctuate across the season (lowest in winter/spring).
We propose that fluctuations in prenatal vitamin D may underlie the association between season of birth and risk of brain tumors. While the mechanism of action underlying this association remains to be determined, it is feasible that the increased cellular proliferation found in the developing brains of embryos exposed to low prenatal vitamin D may contribute to cancer pathways. In light of the fact that vitamin D operates via a nuclear receptor, and enlists a range of transcriptional factors involved in chromatin remodeling, it is also feasible that fluctuations in vitamin D3 may alter epigenetic programs established during early brain development.
If transient prenatal hypovitaminosis D contributes to even a small proportion of cases of brain tumors, it warrants further scrutiny. This putative risk factor is readily addressed via cheap and safe public health interventions such as vitamin supplementation.