VDR and Parkinson disease: There is high‐quality and reproducible evidence that vitamin D is lower in PD cases compared with controls.3, 4, 5 The mechanisms underpinning this association are not clear, but evidence for a causal role comes from preclinical studies showing a neuroprotective effect in animal models6 and the potential association of vitamin D receptor (VDR) polymorphisms with PD, although the studies to date have been inconsistent.7, 8, 9