Researchers looked at 63 different studies involving about 10,700 people to understand how vitamin D connects to Parkinson’s disease. They found that people with Parkinson’s tend to have much lower vitamin D levels than healthy people, and they’re more likely to have vitamin D deficiency. While getting enough vitamin D might help reduce the risk of developing Parkinson’s, taking vitamin D supplements didn’t significantly improve movement problems in people who already have the disease. The study also examined genes related to vitamin D, but the results were mixed and unclear.

The Quick Take

  • What they studied: Whether vitamin D levels, vitamin D supplements, and vitamin D-related genes are connected to Parkinson’s disease risk and symptoms
  • Who participated: About 10,700 people total across 63 different studies, including people with Parkinson’s disease and healthy people without the disease
  • Key finding: People with Parkinson’s have significantly lower vitamin D levels than healthy people. They’re 2.2 times more likely to have severe vitamin D deficiency and 1.5 times more likely to have mild vitamin D insufficiency. Having enough vitamin D may lower the risk of developing Parkinson’s by about 17%, but vitamin D supplements didn’t noticeably help people who already had the disease.
  • What it means for you: If you have Parkinson’s or are concerned about your risk, getting your vitamin D levels checked is worth discussing with your doctor. While maintaining healthy vitamin D levels appears important, taking supplements probably won’t fix movement problems if you already have Parkinson’s. This is early evidence, so more research is needed before making major changes.

The Research Details

This was a systematic review and meta-analysis, which means researchers searched through scientific databases (PubMed, Scopus, and Google Scholar) to find all studies published through August 2025 that looked at vitamin D and Parkinson’s disease. They included 63 different studies with about 10,700 participants total. The studies included different types of research: some followed people over time to see who developed Parkinson’s, some compared vitamin D levels between people with and without Parkinson’s, some tested whether vitamin D supplements helped, and some looked at genes related to vitamin D.

The researchers combined the results from all these studies using statistical methods to get a clearer picture than any single study could provide. They looked at three main questions: Do people with Parkinson’s have lower vitamin D levels? Does vitamin D deficiency happen more often in people with Parkinson’s? And does vitamin D supplementation help improve symptoms? They also examined whether specific genetic variations in the vitamin D receptor gene were linked to Parkinson’s risk.

By combining results from many studies, researchers can see patterns that might not be obvious in individual studies. This approach is especially useful when individual studies have small numbers of participants or conflicting results. A meta-analysis gives us a more reliable answer to important health questions.

This study followed strict international guidelines (PRISMA) for conducting and reporting systematic reviews, which makes it more trustworthy. The researchers registered their plan ahead of time (PROSPERO), which prevents them from changing their methods based on results. However, the individual studies included had different designs and quality levels, which can affect how confident we should be in the combined results. The fact that vitamin D supplementation showed no clear benefit is important—it suggests the relationship between vitamin D and Parkinson’s may be more complex than simply taking supplements.

What the Results Show

People with Parkinson’s disease had significantly lower vitamin D levels compared to healthy people without the disease. The difference was measurable and consistent across studies. Additionally, people with Parkinson’s were much more likely to have vitamin D deficiency (2.2 times higher odds) or insufficiency (1.5 times higher odds) than healthy controls.

When researchers looked at studies that followed people over time, they found that people with adequate vitamin D levels had about a 17% lower risk of developing Parkinson’s disease compared to those with low vitamin D. This suggests that maintaining healthy vitamin D levels might be protective, though it doesn’t prove that vitamin D deficiency causes Parkinson’s.

When people with Parkinson’s took vitamin D supplements, there were only modest improvements in their movement and motor symptoms, and these improvements were not statistically significant. This means the improvements were so small they could have happened by chance. The researchers looked at 20 genetic studies examining whether specific variations in the vitamin D receptor gene increased Parkinson’s risk. One genetic variation called FokI showed the most consistent connection to Parkinson’s, but other genetic variations had unclear or no association with the disease.

The study found that vitamin D deficiency is very common in people with Parkinson’s disease, affecting a large percentage of patients. The consistency of low vitamin D levels across different studies and populations suggests this is a real and widespread pattern, not just a coincidence. The genetic findings were less clear—while one specific gene variation (FokI) appeared in multiple studies, most other genetic variations didn’t show a clear link to Parkinson’s risk, suggesting that genetics alone don’t explain the vitamin D-Parkinson’s connection.

This research builds on earlier studies that suggested vitamin D might be important for brain health and protection against neurological diseases. Previous research had shown that vitamin D plays roles in brain development, immune function, and reducing inflammation—all potentially relevant to Parkinson’s. However, this comprehensive review shows that while low vitamin D is definitely more common in Parkinson’s patients, simply supplementing with vitamin D doesn’t appear to reverse or significantly improve the disease. This suggests the relationship is more complicated than previously thought and that low vitamin D might be a consequence of Parkinson’s rather than just a cause.

The individual studies included in this review used different methods and measured vitamin D in different ways, which can make it harder to combine results accurately. Some studies were small, and some didn’t control for other factors that affect vitamin D levels, like sun exposure and diet. The studies on vitamin D supplementation were limited in number and duration, so we can’t be completely sure supplements don’t help—they might help in ways the studies didn’t measure or over longer time periods. The genetic studies showed conflicting results, making it hard to draw firm conclusions about which gene variations matter. Finally, most studies were observational (watching what happens naturally) rather than randomized controlled trials (where researchers assign people to take vitamin D or placebo), so we can’t be certain about cause and effect.

The Bottom Line

If you have Parkinson’s disease or are at risk, ask your doctor to check your vitamin D levels. If you’re deficient or insufficient, working to improve your vitamin D status through sun exposure, diet, or supplements is reasonable and supported by this evidence (moderate confidence). However, don’t expect vitamin D supplementation alone to significantly improve movement symptoms if you already have Parkinson’s (low confidence). Vitamin D is important for overall health, so maintaining adequate levels is worthwhile for general wellness reasons beyond just Parkinson’s risk.

People with Parkinson’s disease should definitely pay attention to their vitamin D levels. People with family history of Parkinson’s or those concerned about their risk should consider getting their vitamin D checked. Older adults and people with limited sun exposure should be especially attentive, as they’re at higher risk for vitamin D deficiency. People already taking vitamin D supplements for other health reasons can feel confident they’re doing something that may be beneficial. However, this research doesn’t suggest that people without Parkinson’s need to take high-dose vitamin D supplements specifically to prevent Parkinson’s—normal, healthy vitamin D levels appear to be what matters.

If you’re deficient in vitamin D and start supplementing or increasing sun exposure, it typically takes 2-3 months to see meaningful improvements in blood vitamin D levels. If vitamin D deficiency is contributing to Parkinson’s risk, the protective effect would likely develop over years, not weeks or months. If you already have Parkinson’s and start vitamin D supplementation, don’t expect to see improvements in movement or motor symptoms within weeks—the research suggests any benefits would be minimal even with longer-term use.

Want to Apply This Research?

  • Track your vitamin D supplementation (dose and frequency) and note any changes in energy levels, mood, or overall well-being weekly. Also track sun exposure time when possible, as this is a natural source of vitamin D.
  • Set a daily reminder to take vitamin D supplements if your doctor recommends them. Log your supplement intake in the app each day. If appropriate, schedule outdoor time during midday hours 2-3 times per week to support natural vitamin D production.
  • Check in monthly with your vitamin D levels through blood tests (as recommended by your doctor). Use the app to track patterns between vitamin D status and overall wellness metrics like energy, mood, and sleep quality. Share this data with your healthcare provider to inform ongoing management decisions.

This research summary is for educational purposes only and should not replace professional medical advice. The findings suggest associations between vitamin D and Parkinson’s disease, but do not prove cause and effect. If you have Parkinson’s disease, are at risk for it, or are considering vitamin D supplementation, please consult with your healthcare provider before making any changes to your treatment or supplement regimen. This is especially important if you take other medications, as vitamin D supplements can interact with certain drugs. The research shows limited benefit of vitamin D supplements for improving existing Parkinson’s symptoms, so supplements should not be considered a replacement for established Parkinson’s treatments.