n a randomized, double-blind, placebo-controlled study, 112 PD patients (mean age, 72 years) on standard PD treatment were supplemented with 1,200 IU/day of vitamin D or a placebo for 12 months. Vitamin D supplementation nearly doubled serum 25-hydroxyvitamin D concentration (from mean of 22.5 ng/mL to 41.7 ng/mL) in supplemented subjects and limited the progression of PD, as indicated by a greater proportion of patients who showed no worsening (as assessed by the Hoehn and Yahr stage and the United Parkinson Disease Rating Scale part II) in the supplemented group compared to the placebo group (243). It is not known whether vitamin D insufficiency has a role in the pathogenesis of the disease, but the repletion of vitamin D may provide health benefits that go beyond the prevention and/or the treatment of PD. For example, vitamin D deficiency may contribute to the increased risk of osteoporosis and bone fracture in individuals with neurologic disorders, including PD and multiple sclerosis (244-246). Interestingly, sunlight exposure was found to be associated with improved vitamin D status, higher bone mineral density of the second metacarpal bone, and lower incidence of hip fracture in a prospective study conducted in 324 elderly people with PD (247).