CYP2R1 and vitamin D deficiency: Genes involved in vitamin D metabolism and function, such as VDR, CYP2R1 and CYP24A1, are particularly susceptible to DNA methylation due to the presence of large cytosine‐guanine islands in the genes.72 A genome‐wide methylation study found the genes DHCR7, CYP2R1 and CYP24A1 in leucocytes were differentially methylated between participants with vitamin D deficiency compared to those with adequate vitamin D status.73 Modulation of vitamin D activity by epigenetic DNA methylation may have indirect effects on development of food allergies.