Researchers studied whether vitamin D levels affect age-related macular degeneration (AMD), a common eye disease that causes vision loss in older people. They compared vitamin D levels in 100 people with AMD to 110 healthy people. They found that people with AMD had lower vitamin D levels than those without the disease. Interestingly, people with more advanced AMD had even lower vitamin D levels. While these findings suggest vitamin D might play a role in eye health, the researchers note that vitamin D alone cannot reliably predict who will develop AMD. This research adds to growing evidence that vitamin D may be important for maintaining healthy vision as we age.

The Quick Take

  • What they studied: Whether people with a common eye disease called macular degeneration have different vitamin D levels than people with healthy eyes, and if vitamin D levels relate to how severe the disease is.
  • Who participated: 210 people total: 100 with age-related macular degeneration (an eye disease affecting older adults) and 110 healthy people without the disease. All participants were evaluated at a hospital in China.
  • Key finding: People with macular degeneration had lower vitamin D levels (about 23 units) compared to healthy people (about 26 units). People with advanced stages of the disease had even lower vitamin D levels than those in early stages.
  • What it means for you: This suggests that maintaining healthy vitamin D levels may be important for eye health, but it’s too early to say that vitamin D supplements will prevent or treat macular degeneration. Talk to your doctor about your vitamin D levels, especially if you’re concerned about eye health.

The Research Details

This was a cross-sectional study, which means researchers took a snapshot in time of two groups of people and compared them. They measured vitamin D levels in 100 people who already had macular degeneration and 110 healthy people without the disease. All participants had their eyes examined by eye doctors and had blood tests to measure their vitamin D levels and other markers of inflammation and health. The researchers carefully excluded people taking vitamin D supplements or those with conditions that affect how their body uses vitamin D, so the results would be clearer.

The researchers used statistical tests to compare vitamin D levels between the two groups and to look for patterns between vitamin D levels and how severe the eye disease was. They also looked at whether vitamin D levels were connected to other markers in the blood that might relate to inflammation or disease severity.

This study design allows researchers to see if there’s a connection between vitamin D and macular degeneration at a specific point in time. By comparing people who already have the disease to healthy people, they can identify whether vitamin D differences exist. However, this type of study can’t prove that low vitamin D causes the disease—only that they appear together. This is an important first step that might lead to future studies testing whether vitamin D supplements could help prevent or slow the disease.

Strengths: The study carefully selected participants and excluded those taking supplements or with conditions affecting vitamin D metabolism, making the comparison clearer. Researchers used standard medical tests and statistical methods. Limitations: The study only looked at one point in time, so we can’t know if low vitamin D came before the disease or after. The study was conducted at one hospital in China, so results might not apply to all populations. The sample size of 210 is moderate, which limits how confident we can be in the findings.

What the Results Show

People with macular degeneration had significantly lower vitamin D levels (averaging 23 ng/mL) compared to healthy people (averaging 26 ng/mL). While this difference is statistically significant, it’s relatively small in real-world terms. Within the macular degeneration group, those with advanced disease had lower vitamin D levels (22.5 ng/mL) than those with early-stage disease (23.5 ng/mL).

The researchers also found that people with advanced macular degeneration had higher levels of a marker called CRP, which indicates inflammation in the body. This suggests that vitamin D’s anti-inflammatory properties might be relevant to how severe the disease becomes. The connection between vitamin D and inflammation could be one way that vitamin D affects eye health.

When researchers tested whether vitamin D levels alone could identify who has macular degeneration, they found it worked moderately well (about 71% accuracy), but it wasn’t reliable enough to use as a diagnostic test on its own. This means vitamin D is just one piece of a much larger puzzle in understanding macular degeneration.

The study found positive associations between vitamin D levels and two other blood markers: apolipoprotein E (a protein related to cholesterol) and serum creatinine (a marker of kidney function). These connections suggest that vitamin D might be part of a broader network of factors affecting eye and overall health. However, these associations were modest, and their practical importance isn’t yet clear.

This research adds to existing evidence suggesting that vitamin D plays a role in eye health and age-related diseases. Previous studies have hinted at connections between vitamin D and macular degeneration, but results have been mixed. This study provides clearer evidence that lower vitamin D levels are associated with both the presence and severity of macular degeneration. However, other research has also shown that many factors—genetics, smoking, diet, and sun exposure—influence both vitamin D levels and macular degeneration risk, so vitamin D is likely just one part of the story.

This study has several important limitations. First, it’s a snapshot in time, so we can’t determine whether low vitamin D causes macular degeneration or if the disease somehow affects vitamin D levels. Second, the study was conducted at one hospital in China, so results might not apply to people of different ethnicities or in different geographic regions. Third, the researchers excluded people taking vitamin D supplements, which means we don’t know how the findings apply to people actually taking supplements. Finally, the study is relatively small (210 people), which limits how confident we can be that these findings would hold true in larger populations.

The Bottom Line

Based on this research, maintaining adequate vitamin D levels appears to be associated with better eye health, but we cannot yet recommend vitamin D supplements specifically to prevent or treat macular degeneration. Current evidence suggests: (1) Have your vitamin D levels checked as part of routine health care, especially if you’re over 50 or concerned about eye health (moderate confidence); (2) Maintain vitamin D through sunlight exposure, diet, or supplements as recommended by your doctor for overall health (high confidence in general health benefits); (3) Don’t rely on vitamin D alone for eye health—other factors like not smoking, eating antioxidant-rich foods, and protecting eyes from UV light are also important (high confidence).

This research is most relevant to older adults concerned about macular degeneration, people with a family history of the disease, and anyone interested in preventive eye health. People with early signs of macular degeneration might want to discuss vitamin D levels with their eye doctor. However, this research shouldn’t alarm people—macular degeneration has many causes, and low vitamin D is just one potential factor. People without eye concerns don’t need to change their behavior based solely on this study.

If vitamin D does play a role in macular degeneration, benefits from maintaining adequate levels would likely develop over months to years, not days or weeks. Macular degeneration is a slow-progressing disease, so any protective effects of vitamin D would be gradual. If you’re concerned about your vitamin D levels, talk to your doctor about testing and appropriate supplementation based on your individual needs.

Want to Apply This Research?

  • Track your vitamin D levels quarterly (every 3 months) if your doctor recommends monitoring. Record the actual blood test value (in ng/mL) along with the date. Note any changes in eye health symptoms or vision, and correlate these with your vitamin D measurements over time.
  • If your vitamin D levels are low, work with your doctor to increase them through: (1) Spending 10-30 minutes in midday sun several times per week (depending on skin tone and location); (2) Eating more vitamin D-rich foods like fatty fish, egg yolks, and fortified milk; (3) Taking a vitamin D supplement if recommended by your doctor. Use the app to set reminders for sun exposure, track dietary sources of vitamin D, and log any supplements taken.
  • Create a long-term eye health dashboard that tracks: vitamin D blood levels (quarterly), any vision changes or eye symptoms (monthly), dietary vitamin D intake (weekly), sun exposure time (weekly), and other eye health factors like UV protection use and antioxidant-rich food consumption. This comprehensive approach helps you see patterns and share data with your healthcare provider during regular check-ups.

This research suggests an association between vitamin D levels and macular degeneration but does not prove that vitamin D deficiency causes the disease or that supplements will prevent it. This information is for educational purposes only and should not replace professional medical advice. If you have concerns about macular degeneration, vision changes, or your vitamin D levels, consult with an eye care professional or your primary care doctor. Do not start, stop, or change any supplements without discussing with your healthcare provider, especially if you take other medications or have kidney or heart conditions. This single study provides preliminary evidence and should not be the sole basis for medical decisions.