At the completion of this article, the reader should be able to improve their management of dry eye
disease (DED), including:
- Recognise the benefits of the Mediterranen diet and Omega-3 fatty acids in reducing DED symptoms
and inflammation. - Explore the significance of testing and supplementing Omega-3, Vitamin D, and Vitamin B12 levels, particularly in patients with Sjögren’s Syndrome.
- Assess the emerging role of nutraceuticals like curcumin and astaxanthin in the holistic management of DED.
Adele Jefferies
MSc(Hons) BOptom(Hons) CertOcPharm(Therap)
Optometrist & national clinical manager – Matthews Eyecare Eyewear Ltd
President – Cornea & Contact Lens Society of New Zealand
Given the multifactorial nature of dry eye disease, diet, lifestyle changes and nutritional supplements should be considered alongside other approaches. But which ones? ADELE JEFFERIES provides an overview of the latest studies and shows that, as research evolves, nutritional strategies could become an integral part of holistic management.
Dry eye disease (DED) is a complex, multifactorial condition that can profoundly affect our patients’ quality-of-life. While topical treatments remain the cornerstone of DED management, the role of lifestyle factors, including diet and nutrition, is becoming increasingly understood. Patients may also read many ‘facts’ online, so understanding the current evidence can assist in their clinical care. Nutritional approaches offer a complementary strategy that enhances overall health and helps target some of the underlying mechanisms of DED, including inflammation.
The role of hydration
Adequate hydration is fundamental to maintaining the body’s overall health, and dehydration is common in the elderly. While good hydration feels like a logical consideration for DED, the evidence is not definitive – while dehydration has been linked to increased tear osmolarity,1 other population-based research has reported no link between higher water intake and the risk of DED.2 The ‘Tear Film & Ocular Society’s (TFOS) Lifestyle Report’ concluded that “increased water intake has not been directly tied to improved dry eye or ocular surface outcomes” and that future longitudinal studies are needed.3 Nevertheless, due to the general health benefits of good hydration, it is still something I actively recommend to patients.
A simple dietary approach
When it comes to nutrition, there is a principle idea that ‘whole food’ is more beneficial than the individual parts, so recommending an overall dietary approach may have advantages over recommending supplements.
While there are a lot of diet trends, the only diet with evidence for improvement for DED is the Mediterranean diet.3 This diet is more a way of eating than a prescriptive diet; it’s based on the traditional eating patterns in countries near the Mediterranean Sea, including Greece, Spain, Italy, North Africa and the Middle East.
The Mediterranean diet focuses on minimally-processed foods; it’s high in monounsaturated, polyunsaturated, and Omega-3 fatty acids; and it is low in saturated fats, added sugars and sodium. Olive oil is the primary fat source; it is high in plant-based foods; it features a moderate-to-high seafood intake, moderate dairy consumption; low-to-moderate consumption of wine, and limited intake of red meat, sweets and white flour.
The Mediterranean diet has been shown to have antioxidant and anti-inflammatory properties, improve gut health and be beneficial in several health conditions, including cardiovascular disease, Alzheimer’s, psoriasis and depression.3 It has also been shown to be associated with a lower likelihood of developing Sjögren’s Syndrome.4
A small 2020 study examined the impact of the Mediterranean diet supplemented with extra virgin olive oil and nuts (standard intervention) and a hypocaloric Mediterranean diet combined with an intensive lifestyle program with physical activity and weight loss (intensive intervention). The authors found that in both patient groups, the ocular surface disease index (OSDI), tear breakup time (TBUT), Schirmer score, and Oxford staining scores improved after six months, but more significant improvements were seen in TBUT, Schirmer and staining scores in the intensive intervention group.5
The puzzle pieces
Our diets are made up of macro- and micronutrients, and there is growing research on how these individual components and their supplementation may impact our patients’ ocular surface health.
Fatty Acids
One of the most-studied nutritional interventions for DED is omega fatty acids, primarily eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). While some study results are conflicting, and there is still more to be known, Omega-3 in the diet or via supplementation has been shown in various studies to improve many aspects of DED.
Omega-3
The 2019 Cochrane review summarised 34 randomised control trials, and the consensus was that signs of DED improved with oral supplementation of Omega-3, and symptoms improved when Omega-3 was combined with other dry eye treatments, such as lubricants and warm compresses.6 A 2019 meta-analysis examined 17 clinical trials and found significant improvements in signs and symptoms, particularly in populations with lower intake of fish in their diets.7 Unfortunately, there is no current consensus on treatment guidelines, including the composition, dose and treatment duration.
Omega-6
As the ratio of Omega-6 to Omega-3 is important, patients can consider reducing sources of inflammatory Omega-6 in their diet or including more Omega-3-rich foods in their diet, such as fatty fish (salmon, mackerel, tuna and sardines), as well as flaxseed, chia seeds and walnuts. They could also consider getting their blood levels of Omega-3 tested.
Based on the research, if patients are interested in trialling supplementation as part of their management strategy, I recommend they trial a re-esterified/triglyceride formula with between 1500-3000mg EPA/DHA per day for three months. I then review their signs and symptoms to confirm the benefit for that individual patient. Due to the additional benefits discussed later in this article, there may be added therapeutic benefits if the Omega-3 supplement contains GLA and/or Vitamin D.
Notes on dietary supplements
When supplementing, you want to advise patients that they may cause gastrointestinal side effect,3 and while there is the theoretical potential for Omega-3 supplements to cause an increased risk of increased bleeding, it is typically only a concern in doses over 3000mg, in elderly patients on blood thinning medications and in those with haemophilia.3,7
If the patient is vegan or vegetarian, they could consider flaxseed oil, which contains the short-chain Omega-3 Alpha-linoleic Acid (ALA), but as ALA converts to DHA/EPA in the body, a higher dose is needed, with 6g/day being shown to improve symptoms, TBUT and meibum score.3
In addition to Omega-3 fatty acids, Gamma Linolenic Acid (GLA) – found in sources like borage oil and black currant seed oil – has shown significant anti-inflammatory activity. GLA works by inhibiting the conversion of Omega-6 fatty acids into pro-inflammatory compounds. Clinical studies have demonstrated that a daily intake of 15mg of GLA can improve symptoms, reduce ocular surface staining, and decrease inflammation.8
Micronutrients
Micronutrients are the vitamins and minerals in food that affect many bodily functions. There are 13 essential vitamins and 16 essential minerals for human health. The major vitamins associated with ocular surface disease are currently thought to be vitamins A, B12, C and D.3
Vitamin A
Vitamin A, essential for cell differentiation, development and function, is the most frequent form of malnutrition contributing to ocular disease in the developing world.3 It is a fat-soluble vitamin found in many foods, including liver, butter, cheese, eggs, fish, sweet potato, carrot, broccoli, sweet red pepper, spinach and lettuce. In developed populations like Australia and New Zealand, poor intake is uncommon.
Vitamin A is beneficial to the ocular surface, having antioxidant properties, reducing corneal epithelial apoptosis, increasing conjunctival mucin expression, promoting corneal and conjunctival wound healing and preventing goblet cell loss.3 Still, investigations on the impact of oral intake of vitamin A are limited. In 1982, a small study of patients with severe deficiency benefited from oral vitamin A with improved goblet cell numbers and density and improved corneal epithelisation;9 a 2019 study found that in those without a vitamin A deficiency, oral supplementation improved quality (tear ferning), but not quantity of tears.10
B vitamins
B vitamins are found in various foods, including whole grains, meat, eggs and dairy products, legumes, seeds and nuts and dark green vegetables. Deficiencies in the water-soluble B vitamins (thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folate (B9) and cobalamin (B12)) are also uncommon, but do increase with age.3
B12 deficiency appears to have the most significant role in DED – it’s been associated with an increased risk of DED3 and neuropathic pain.11,12 Additionally, 10-25% of patients with Sjögren’s Syndrome have also been found to have a vitamin B12 deficiency.11 The benefit of supplementation has also been demonstrated – three months of vitamin B12 supplements in patients with both a vitamin B12 deficiency and neuropathic ocular pain, was shown to nearly halve their OSDI score and to increase tear secretion.12
Vitamin C
Vitamin C has antioxidant, anti-inflammatory and immunomodulatory functions. It is present on the ocular surface; as it’s found in fruit and vegetables, deficiencies are very uncommon.3
Vitamin D
Vitamin D’s role in dry eye disease is becoming widely recognised. This fat-soluble essential vitamin has antioxidant, anti-inflammatory and immune-
regulatory effects.13 Deficiencies can be common. Vitamin D deficiency has been linked to increased tear film instability,14 lower tear secretion,13,14 lower Schirmer’s Test,13,14 hyperosmolarity13,14 and increased symptoms.11 Supplementation has also been shown to improve these signs and symptoms of dry eye in those with a deficiency.3,15
Our Vices
Coffee
I, and many others, are partial to beginning our days with a cup or two of coffee. While the health benefits of coffee may be debated, the prevalence of DED has been found to decrease as coffee consumption increased from less than one cup per day to up to three cups per day,16 and the study authors concluded that there was no significant relationship between the frequency of coffee consumption and DED.16 In other research, higher caffeine intake is associated with a reduced risk of dry eye disease.17
Alcohol
The role of alcohol on dry eye is mixed. Alcohol has been found to be secreted into the tears,18 to increase tear film osmolarity,18 to shorten tear film break-up time18 and to increase the risk of DED symptoms.19 Further, a 2016 meta-analysis concluded there was a borderline significant positive association between dry eye and alcohol use, but that there was no clear increased risk of dry eye in heavy drinkers.18 The authors postulated that there may be a protective effect of neuropathy on dry eye symptoms in heavy drinkers.18
In 2021, our knowledge was further refined with insights including that alcohol intake significantly increased the risk of symptomatic dry eye in females, but not males.19 It also confirmed that older patients and heavier drinkers were likely to have alcohol-induced peripheral neuropathy, leading to decreased corneal sensitivity and, therefore, fewer symptoms.19
Emerging Nutraceuticals
Curcumin
Curcumin, the primary curcuminoid found in turmeric, is a yellow polyphenol with well-documented anti-inflammatory and antioxidant properties.3,20 Research, including several in vitro and animal studies, has demonstrated the beneficial effects of topical curcumin in preventing corneal neovascularisation, promoting corneal wound healing, and inhibiting the pathological mechanisms associated with allergic conjunctivitis, pterygium and corneal endothelial dysfunction.3,20
Although further research is necessary to understand the potential benefits of dietary curcumin for DED, animal studies suggest that oral curcumin may enhance tear volume, improve TBUT, and reduce inflammatory markers in tears.20 Notably, a recent double-masked randomised controlled trial found that an eight-week regimen of a supplement containing curcumin, lutein, zeaxanthin and vitamin D3 significantly improved ocular symptoms, Schirmer scores, TBUT and corneal staining scores, indicating a promising role for curcumin in managing dry eye.21
Honey
Honey has been shown to have antibacterial, antifungal, antiviral, anti-inflammatory and antioxidant properties. Several randomised clinical trials have investigated the effect of topically applied Manuka honey (Leptospermum spp.) and its benefits on improving tear film evaporation, meibomian gland dysfunction and blepharitis.3 The effect of oral intake of honey on ocular surface disease has not been comprehensively studied. One double-masked randomised controlled trial investigated the effect of oral royal jelly, finding improvements in tear break-up time and Schirmer scores, but no improvement in symptoms.3
Astaxanthin
Astaxanthin, a red-pigmented marine carotenoid found in organisms like algae and shrimp, is part of the xanthophyll family, closely related to lutein and zeaxanthin.
Known for its potent antioxidant and anti-inflammatory properties, astaxanthin has shown potential in managing DED by reducing oxidative stress on the ocular surface and lowering the levels of pro-inflammatory cytokines and reactive oxygen species in tears. Studies suggest that astaxanthin can improve tear production and stability, thereby alleviating symptoms of dry eye.22
Probiotics
There have also been correlations between gut dysbiosis and dry eye severity,23,24 and dry eye patients have been found to have reduced gut microbiota diversity compared to controls.23 In 20 patients with DED, 30-day supplementation of B. lactis and B. bifido significantly increased tear secretion and tear break-up compared to placebo,25 and the combination of IRT-5 probiotics (Lactobacillus casei, Lactobacillus acidophilus, Lactobacillus reuteri, Bifidobacterium bifidum, and Streptococcus thermophilus) has been shown to reduce ocular staining and improve tear secretion.26 An Australian, double-masked randomised clinical trial examined the impact of oral probiotics and prebiotics in managing DED over a four months and found an improvement in symptoms.27
Final thoughts
DED requires a multifaceted treatment approach, and attention to nutrition and lifestyle factors offers a valuable opportunity to improve patient outcomes. Recommending a Mediterranean diet, a good intake of Omega-3 and antioxidants, maintenance of good gut health and adequate hydration can be an effective adjunct to conventional treatments.
Additionally, eyecare providers could consider referral to the patient’s general practitioner or a dietician to test Omega-3, Vitamin D and Vitamin B12 levels, particularly in Sjögren’s Syndrome patients.
Ultimately, as research in this area continues to evolve, nutritional strategies may become increasingly integrated into the standard care for DED to offer a holistic approach to managing this common and often debilitating condition.
More reading
Dry eye: Patient identification, product formulation and therapy escalation
Exposing the underlying factors contributing to dry eye
Report details dry eye therapies with important clinical potential
References
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