Randomized, double-blind, placebo-controlled trial of vitamin D supplementation in Parkinson disease.

Randomized, double-blind, placebo-controlled trial in adults with Parkinson disease aged 45-85 years at Katsushika Medical Center in Tokyo, Japan. The vitamin D3 arm included 55 participants, with 57 in the placebo arm; all were receiving standard Parkinson disease therapy.

Vitamin D3 (cholecalciferol) was given orally as a tablet at 1200 IU/day for 12 months. The comparator was an identical-appearing placebo tablet.

Vitamin D3 generally favored slower Parkinson disease progression, with benefit most apparent in patients with VDR FokI TT or CT genotypes. Hoehn and Yahr stage changed less in the vitamin D3 group than in placebo (+0.02 ± 0.62 vs +0.33 ± 0.70; P = 0.005), and more vitamin D3 participants had no worsening or improvement in HY stage (29.1% vs 12.3%; RR 2.37, 95% CI 1.06-5.31; P = 0.028). UPDRS total did not differ significantly (P = 0.11), but UPDRS part II and several PDQ-39 domains favored vitamin D3, including no worsening or improvement in UPDRS part II (47.3% vs 28.1%; RR 1.68, 95% CI 1.02-2.78; P = 0.036) and better activities of daily living and emotional well-being scores. Hypercalcemia was not observed, and serum calcium remained within the normal range.

The trial was relatively small, and the genotype-specific conclusion limits generalizability. Follow-up was only 12 months, some outcomes were not significant, and one serious adverse event with loss to follow-up occurred in the vitamin D3 group. The study was conducted at a single center in Japan, which may reduce external validity.