A large study of over 400,000 people in the UK found that those with low vitamin D levels were more likely to develop cataracts - cloudy areas in the eye that can cause vision problems. The researchers followed participants for nearly 11 years and discovered that people with severely low vitamin D had up to 27% higher chances of getting cataracts, especially if they were younger. This suggests that maintaining healthy vitamin D levels through sunlight, diet, or supplements might help protect your vision as you age.

The Quick Take

  • What they studied: Whether people with low vitamin D blood levels are more likely to develop cataracts (cloudy patches in the eye that blur vision)
  • Who participated: Over 442,000 adults from the UK, with nearly 428,000 followed for about 11 years to see who developed cataracts
  • Key finding: People with severely low vitamin D (below 25 nmol/L) had 11-27% higher risk of developing cataracts, with younger people being most affected
  • What it means for you: Keeping your vitamin D levels healthy through sun exposure, diet, or supplements may help protect your vision, especially if you’re under 60

The Research Details

This study used data from the UK Biobank, a massive health database that tracks hundreds of thousands of people over time. Researchers measured vitamin D levels in participants’ blood and looked at two things: who already had cataracts at the start (cross-sectional analysis) and who developed cataracts during the follow-up period (longitudinal analysis). They divided participants into groups based on their vitamin D levels, from severely deficient to optimal, and compared cataract rates between these groups.

This approach is powerful because it includes both a snapshot in time and long-term tracking. The longitudinal part is especially valuable because it can show whether low vitamin D actually comes before cataract development, rather than just being associated with it. Following people for over 10 years gives confidence that the vitamin D levels measured at the beginning influenced future eye health.

The study’s massive size (over 400,000 people) makes the results very reliable. The UK Biobank is known for high-quality data collection and standardized measurements. However, vitamin D was only measured once at the beginning, so changes over time weren’t captured. The study also couldn’t prove that low vitamin D directly causes cataracts, only that they’re connected.

What the Results Show

The study found a clear pattern: the lower someone’s vitamin D level, the higher their risk of cataracts. People with severely low vitamin D (below 25 nmol/L) were 11% more likely to develop cataracts overall compared to those with adequate levels. However, age made a big difference in this risk. Younger people under 50 with severe vitamin D deficiency had a 27% higher risk, while those 50-60 years old had 12% higher risk, and people over 60 had only 9% higher risk. This suggests vitamin D may be most important for eye health in younger adults.

The researchers found that even mild vitamin D deficiency increased cataract risk, though not as dramatically as severe deficiency. The protective effect of higher vitamin D levels was consistent across different types of cataracts and remained significant even after accounting for factors like age, sex, lifestyle, and other health conditions that might influence both vitamin D levels and eye health.

Previous studies on vitamin D and cataracts have shown mixed results, with some finding protective effects and others showing no connection. This study is much larger than most previous research and includes long-term follow-up, which strengthens the evidence for a real relationship. The finding that younger people benefit more from adequate vitamin D is relatively new and hadn’t been clearly shown before.

The study only measured vitamin D once, so it couldn’t account for changes in levels over the 11-year follow-up period. Most participants were of European ancestry, so results might not apply equally to all ethnic groups. The study also couldn’t determine the optimal vitamin D level for eye health or whether taking supplements would definitely prevent cataracts, since it only observed natural vitamin D levels.

The Bottom Line

Based on this research, maintaining adequate vitamin D levels appears beneficial for eye health, especially for people under 60. Aim for vitamin D blood levels above 50 nmol/L through sensible sun exposure, vitamin D-rich foods like fatty fish and fortified dairy, or supplements if recommended by your healthcare provider. However, don’t expect vitamin D alone to prevent all cataracts, as age and genetics also play major roles.

This research is most relevant for adults under 60 who want to protect their long-term vision health. People with limited sun exposure, darker skin, or living in northern climates may be at higher risk for vitamin D deficiency. However, anyone concerned about cataracts should discuss their individual risk factors with an eye care professional rather than relying solely on vitamin D optimization.

Since cataracts typically develop slowly over years or decades, any protective effects of maintaining good vitamin D levels would likely take years to become apparent. The study followed people for over 10 years to see these effects, suggesting that vitamin D’s impact on eye health is a long-term process rather than something you’d notice quickly.

Want to Apply This Research?

  • Track your daily vitamin D intake from food sources and supplements, aiming for 600-800 IU daily as recommended by health authorities, and log time spent outdoors for natural vitamin D production
  • Add vitamin D-rich foods like salmon, mackerel, fortified milk, and egg yolks to your meal planning, and consider brief daily outdoor activities to support natural vitamin D synthesis
  • Request vitamin D blood level testing during annual health checkups and track results over time, noting any correlation with dietary changes, supplement use, or seasonal variations in sun exposure

This information is for educational purposes only and should not replace professional medical advice. Consult with your healthcare provider or eye care specialist before making significant changes to your vitamin D intake or if you have concerns about cataract risk. Individual vitamin D needs vary based on factors like skin color, geographic location, and existing health conditions.