Nutritional Supplements For Dry Eye Syndrome

Introduction

Dry eye syndrome, also known as keratoconjunctivitis sicca (KCS) or keratitis sicca is a very common condition affecting the eyes. Tears are essential for keeping the eyes in good health and comfort. However, limited amount of tears due to lack of production or poor quality tears can lead to dry eyes. When we blink, tears coat the cornea of our eyes to maintain a smooth and clear surface of the eye. This is known as a tear film and is composed of layers of oil, water, and mucus which is essential to keep our eyes moist and allow us to have clear vision.

It is estimated that around 50% of adults experience dry eyes.¹ It is more common in adults over the age of 50 years, affecting mostly people assigned females at birth (AFAB) than people assigned males at birth (AMAB).² Nutritional supplements like vitamins, minerals, and fatty acids have been shown by many studies to help with dry eyes. This is because foods with nutritional supplements can contribute to improving the overall quality and quantity of tears.³ Alternatives to nutritional supplements can include the use of artificial tears, surgery, and certain prescribed medications.⁴

Causes and symptoms of dry eye syndrome

Many factors contribute to dry eyes, both genetics and environmental factors. There have been studies that have shown that dry eyes can be inherited from both parents and grandparents with higher prevalence in people with  Asian background.^1,5 In addition, certain medical conditions like rheumatoid arthritis, diabetes, and thyroid problems also increase the likelihood of dry eyes.⁵

Environmental factors that contribute to dry eye syndrome

• Nutritional deficiencies: Deficiency of several nutrients including vitamin A, C, D, E, B12, Zinc, and omega-3 fatty acids can contribute to dry eye syndrome³
• Computers: Staring at computer screens for long periods can reduce blinking, leading to dry eyes. In addition, it is believed that the blue light emitted from computer screens and other electronics can also contribute to dry eyes⁶
• Contact lenses: Oxygen is essential in tear production and contact lenses limit this resulting in the formation of fewer tears and dry eyes. Therefore it is advisable not to wear contact lenses for long periods, and use eye drops if necessary to keep the eyes moist⁷
• Medications: There are certain medications that reduce tear production, which ultimately contribute to dry eyes. Some of these medications include antihistamines, decongestants, blood pressure medications, and antidepressants¹ 
• Climate: Certain environmental conditions like wind, smoke, and dry climates can promote evaporation of tears leading to dry eyes¹  
• Smoking and Alcohol: There have been studies linking smoking and alcohol with many eye conditions including dry eyes^8.9

Common symptoms of dry eye syndrome

• Dryness and irritation of the eyes
• Burning or stinging sensation in the eyes
• Sensitivity to light
• Blurred vision
• Eye fatigue
• Excessive tearing
• Redness of the eyes

Nutritional supplements for dry eye syndrome

Omega-3 Fatty Acids

Omega-3 fatty acids are essential in tear production. Omega-3 fatty acids contribute to the production of the layer of oil in the tear film which is important in the lubrication of the eyes.¹⁰ There have been many studies linking omega-3 fatty acids with improving the quality of tears and reducing the rate of tear evaporation.¹⁰ It also reduces inflammation including pain and irritation. Together all these properties contribute to reducing dry eye syndrome.³

Food sources

• Fish including mackerel, cod, tuna, trout, herring, salmon
• Oils including canola oil, rapeseed oil, flaxseed oil, soybean oil, walnut oil
• Walnuts
• Dairy products like cheese, yogurt, and milk
• Some animal products such as eggs, beef, and chicken

Vitamin A

Vitamin A deficiency has been linked to causing eye problems including dry eyes. This is because vitamin A is an important fat-soluble vitamin that contributes to tear formation. There has been research suggesting that vitamin A also plays a role in improving the smoothness of the tear film.³

Food sources 

• Pumpkins
• Apricots
• Carrots
• Tomatoes
• Spinach
• Dairy products

Vitamin D

Vitamin D has been shown in several studies to reduce dry eyes by improving the quality of tears and relieving symptoms associated with dry eyes. In addition, it also has anti-inflammatory properties reducing inflammation on the surface of the eyes.³ Vitamin D can be obtained from the sun, but there are also several food sources.

Food sources

• Oily fishes like salmon, mackerel, and sardines
• Red meat, liver
• Egg yolk

Vitamin E

Vitamin E is an essential vitamin used in the protection of the eyes against several things such as cell damage and dry eyes.¹¹

Food sources 

• Mackerel
• Spinach
• Peppers
• Mangos
• Red currants

Vitamin B12

Vitamin B12 is mostly associated with contributing to the formation of DNA and nerve fibres. However, there is evidence showing that vitamin B12 deficiency leads to severe dry eyes and eye pain. Researchers have suggested that vitamin B12 repairs the cornea and the nerve layer of the eye and reduces the symptoms of burning commonly associated with dry eye syndrome.³

Food sources

• Liver of animals such as beef, calf, and pork
• Mackerel
• Dairy products 
• Eggs

Vitamin C

Vitamin C has antioxidant properties that can reduce the levels of oxidative stress and fight free radicals, hence reducing the risk of many eye diseases including dry eye syndrome. Due to these properties, vitamin C can improve the stability of the tear film.³

Food sources 

• Fruits including oranges, strawberries, papaya, kiwi, cantaloupe, mango, grapefruit, melon
• Grape juice 
• Vegetables including bell peppers, broccoli, kale, brussels sprouts, snow peas, mustard greens

Zinc

Zinc is essential in the transportation of vitamins like vitamin A from the liver to the retina ultimately contributing to dry eye syndrome. In addition, it also contains melanin which is important in the protection of the eyes.¹²

Food sources

• Whole grains
• Dairy foods
• Sweet corn
• Peas
• Lentils
• Nuts

Lutein and zeaxanthin

The two antioxidants lutein and zeaxanthin have been proven to have beneficial effects related to eyes and dry eye syndrome.¹³ They have been proven to help with many chronic eye diseases and ensure the correct function and health of the cells.

Food sources¹⁴

• Kale
• Spinach 
• Romaine lettuce

Recommended dosages of nutritional supplements

Daily recommended doses for each supplement

For each nutritional supplement, the recommended dietary allowance (RDA) varies. It is suggested, that the daily intake that an average adult consumes is:

• Omega 3 fatty acids: 1000 mg
• Vitamin A: 700 µg (for AFAB), 900 µg (for AMAB)
• Vitamin D: 15 µg (600 IU)
• Vitamin E: 15 mg
• Vitamin B12: 2.4 µg 
• Vitamin C: 75 mg (for AFAB), 90 mg (for AMAB)
• Zinc: 8 mg (for AFAB), 11 mg (for AMAB)

Possible risks of overconsumption

Whilst all the nutrients mentioned above have very good health benefits and can aid in the reduction of dry eye syndrome, it is essential not to over-consume, and to consume everything in moderation. For example, exceeding vitamins like vitamin A and D by consuming more than 5000 IU (1500 µg) and 4000 IU (100 µg) respectively, can lead to toxicity. Some of the symptoms of toxicity include headaches, fatigue, muscle and bone pain, blurring of vision.^15,16

Summary

Dry eye syndrome is a chronic disorder resulting in symptoms such as dryness and irritation of the eyes. There are certain environmental factors like exposure to wind, computers, and the use of contact lenses that can make dry eye syndrome worse. However, the good news is that there are several nutritional supplements including vitamins and minerals that can help alleviate the symptoms of dry eyes. Whilst these nutritional supplements are very good and found in a variety of food sources, it is important not to over-consume as it may lead to toxicity and unwanted side effects.