…daily supplementation with 1200 IU vitamin D3 for 12 mo significantly prevented the deterioration of PD….https://academic.oup.com/ajcn/article/97/5/1004/4577000…. as measured with the HY stage, UPDRS part II and total, and some domains of the PDQ39, with no apparent increase in risk of hypercalcemia or other adverse events during the study period. A point estimate of the number needed to treat was 6 patients for no worsening or improvement in the HY stage, which was considered very effective. To the best of our knowledge, this is the first randomized trial to examine the effects of vitamin D3 in patients with PD. However, a meta-analysis showed that supplemental vitamin D for older adults who participated in randomized controlled trials consistently showed beneficial muscle effects on strength and balance (27). Therefore, it cannot be distinguished whether vitamin D supplementation specifically delays the progression of PD or whether it just nonspecifically improves muscle strength and balance in older adults.