Dry eye disease (DED) affects millions of people worldwide and remains one of the most common reasons patients seek eye care.
While artificial tears, prescription medications, and lifestyle modifications are commonly used to manage symptoms, researchers have increasingly explored whether nutrition may also play a role.
For example?
Vitamins are involved in numerous biological processes, including immune regulation, inflammation control, tissue repair, and nerve function.
Because many of these pathways are involved in ocular surface health, researchers have questioned whether nutritional deficiencies or targeted supplementation could influence dry eye symptoms.
Which brings us to this latest research?
Indeed. A recent systematic review published in Ophthalmic and Physiological Optics examined the available evidence on oral vitamin supplementation for DED.
Noted. And what exactly was reviewed?
Investigators conducted a systematic review following established evidence-review guidelines and searched the literature for studies evaluating oral vitamin supplementation in patients with DED published between 2017 and 2023.
To be included, studies had to assess recognized dry eye outcomes such as:
- Schirmer testing
- Tear film break-up time (TBUT)
- Corneal fluorescein staining (CFS)
- Ocular Surface Disease Index (OSDI) scores
- Lid hyperemia
- Pain scores
The review ultimately identified 13 eligible studies published between 2017 and 2023.
Who were the participants?
Researchers reviewed 13 previously published studies examining oral vitamin supplementation in people with DED.
- Across all included studies, a total of 483 participants were evaluated. Individual study sizes ranged from nine to 94 patients.
To note: Because each study used its own patient population and methodology, the participants varied considerably between studies, making direct comparisons difficult.
Which vitamins were actually studied?
The available literature was surprisingly limited.
Among the 13 studies included in the review:
- Eight evaluated Vitamin D
- Three evaluated Vitamin A
- Two evaluated Vitamin B1 combined with mecobalamin, an active form of Vitamin B12
The studies included follow-up periods ranging from several days to 6 months.
Well, what did they find?
The results were mixed.
- Several studies reported improvements in dry eye symptoms, tear film stability, or ocular surface measurements after supplementation.
- Vitamin D studies most frequently reported improvements in patient-reported symptom scores, while some Vitamin A and Vitamin B studies also showed favorable outcomes.
However, the findings were not consistent across studies—with some investigations reporting improvements in TBUT and Schirmer scores, and others finding little or no significant benefit.
And as a result?
The reviewers concluded that the available evidence does not currently support routine vitamin supplementation as an evidence-based treatment for dry eye disease.
Did any particular vitamin look more promising?
Vitamin D generated the largest body of evidence and some of the most encouraging results.
- Many of the Vitamin D studies reported improvements in symptom scores, which researchers noted may be biologically plausible given its role in immune regulation and inflammation.
- The Vitamin D regimens evaluated across studies varied substantially, ranging from 1,000 IU to 6,000 IU daily—while other studies used 50,000 IU weekly dosing schedules or individualized supplementation based on participants' serum Vitamin D levels.
Vitamin A and Vitamin B-complex supplementation also showed potential benefits in certain studies, particularly for symptom-related outcomes.
However, the reviewers emphasized that the current evidence remains too limited and inconsistent to support routine clinical recommendations.
Editor’s note: Check out our coverage on the potential role of B vitamins in reducing the risk for AMD development—and slowing its progression.
Noted. So were there any limitations to this study?
Although the review identified 13 studies, the authors found that none met the criteria for high-quality evidence. Several issues appeared repeatedly throughout the literature, including:
- Small sample sizes
- Short follow-up periods
- Inconsistent outcome measures
- Methodological weaknesses that increased the risk of bias
The researchers also noted substantial variation between studies, making direct comparisons difficult.
Among these: the vitamin type studied; supplement dosages; treatment duration; patient populations; and outcome measures.
Any others?
Another challenge was that some studies evaluated vitamin supplementation alone, while others combined vitamins with conventional dry eye treatments.
As a result, it was often difficult to determine whether any observed improvements were attributable to the supplements themselves.
The review also highlighted several gaps in the existing literature:
- Most studies focused on Vitamin D
- Relatively few examined Vitamins A or B-complex supplementation
- No eligible studies evaluated Vitamin C supplementation
- Many studies did not assess participants' baseline vitamin status before treatment
Because of these limitations, the authors concluded that current evidence remains insufficient to determine whether oral vitamin supplementation is an effective treatment for dry eye disease.
What about safety concerns?
The review found relatively little information regarding adverse events.
While none of the included studies reported major safety concerns, the authors noted that excessive supplementation can carry risks. For example, high doses of vitamin A may lead to toxicity, while excessive vitamin D intake can cause complications, such as hypercalcemia.
For that reason, the authors stressed the importance of appropriate clinical evaluation before recommending supplementation.
So what’s the takeaway for clinicians?
While the researchers stated that nutrition deserves more attention in dry eye research, they cautioned against assuming that biologic plausibility automatically translates into clinical benefit.
As such, future studies should include:
- Larger patient populations
- Standardized outcome measures
- Baseline nutritional assessments
- Well-defined vitamin formulations
- Stronger randomized-controlled trial (RCT) designs