More studies are needed to show conclusive benefits on patient functionality.
Previous research has linked vitamin D supplementation to improved functionality in patients with Parkinson Disease (PD). Vitamin D is a fat-soluble vitamin that is important for bone and muscle health and strength, and patients with PD tend to have lower serum vitamin D concentrations.
While vitamin D supplementation may improve some aspects of functionality, the body of literature remains quite limited, according to a systematic review published in Clinical Nutrition Open Sciences.
PD is the most common type of neurodegenerative disease and significantly contributes to morbidity and disability. Patients with PD lose dopamine-producing cells in the brain which can cause movement/emotional issues, manifesting as slow movement, muscle rigidity, tremors, and loss of automatic movements; other symptoms can include verbal and written disability, depression, and short-term memory loss.
Vitamin D is thought to prevent PD by regulating calcium ions in the dopaminergic nerves. It is neuroprotective, as well as beneficial to the nervous and immune systems. Those with a vitamin D deficiency may be at risk of developing PD because they will produce less nerve growth factor and brain-derived neurotrophic factor (BDNF), and low serum vitamin D may be associated with increased inflammation.
There is limited research on the efficacy of vitamin D supplementation for PD, so investigators conducted a systematic review of available randomized controlled trials (RCTs) to better understand vitamin D as a therapeutic agent to manage PD and associated symptoms.
There were 4 trials included in the systematic review. Most of these trials defined outcomes as disease progression, balance, strength, and length of dyskinesia, and there was a wide range of doses evaluated (1000 to 10,000 IU/d). Among all the studies, 3 reported improved outcomes with vitamin D supplementation.
Some RCTs connected vitamin D with improved functionality—there were heterogenous results that vitamin D supplementation is associated with a better score on a 6-minute walking test; however, it was not positively linked to a better 10-minute walking test.
Two studies used the timed up-and-go test to measure functionality, and both reported different outcomes (1 highlighted improvement, 1 reports no change). Another test evaluated balance and falls, however there were no significant differences between the supplement and control arms.
Investigators in 1 study administered the Hoehn and Yahr scale to evaluate vitamin D efficacy and observed a positive link between vitamin D and less deterioration. Another study administered the Unified PD rating scale, but investigators reported no improvement in patient condition.
The study includes multiple limitations. First, not all the studies may have administered the optimal vitamin D dosage, and not every participant may have been compliant to their vitamin D regimen. Further, investigators did not evaluate other vitamins or patients’ daily nutritional habits.
“Some isolated beneficial effects of vitamin D were reported on functional scales and tests, but more studies are needed to draw safe conclusions regarding its supplementation in PD,” investigators wrote in the article.
Detopoulou P, Voulgaridou G, Saridaki A, et al. Vitamin D in Parkinson's disease: A systematic review of randomized controlled trials. Clin Nutr Open Sci 52; December 2023, Pages 1-13. doi.org/10.1016/j.nutos.2023.09.005.