Can diet play a role in eye health?

Bridget Scrogings
Accredited Practising Dietitian

Too often people wait until their eyesight is deteriorating to take an interest in their eye health.

Yet the focus should be shifted towards the current body of evidence, which outlines the importance of, and the ways to, prevent the progression of eye diseases early on.⁵

The eye has a significantly higher concentration of polyunsaturated fatty acids than other body tissues, with the highly unsaturated nature allowing them to transmit light signals very quickly.⁶

These polyunsaturated fatty acids within the eye, and particularly the retina, are exposed to excessive amounts of UV light each day.

Unfortunately, this specialised structure and function of the eyes also makes them particularly vulnerable to destruction through oxidation by free radicals, which is the key etiology implicated in the development of eye disease.⁶

To offset the negative factors the eyes deal with on a day-to-day basis, the retina has one of the highest rates of metabolism of any normal tissue in the body³ — which inherently means nutrients need to be resupplied on a regular basis.

But which nutrients should people be aware of when it comes to protecting their eyes?

Are carrots the answer?

The most promising research connecting nutrition and eye health involves the carotenoids, the family of nutrients that provide the yellow, orange and red colors in many fruits and vegetables² — which is how the humble carrot received its glowing reputation.

While carrots are certainly rich in carotenoids, it’s important to emphasise the value of variety.

When it comes to both wholefoods and supplementation, research has demonstrated the combination of nutrients appears to generate the most favourable effects due to synergy.²

Carotenoids: beta-carotene, lutein and zeaxanthin

Within the family of carotenoids, beta-carotene is the orange-yellow carotenoid that the human body can use to make vitamin A; the building block for rhodopsin, which assists with vision at night.^4,7

Good sources of beta-carotene are carrots, sweet potatoes, pumpkin and spinach.

Some less well known carotenoids are lutein and zeaxanthin which, unlike beta-carotene, do not get converted into vitamin A, but rather act as antioxidants within the eye.³

Studies have identified lutein and zeaxanthin to be essential components for eye health, with both being detected in concentrated amounts in the human retina at the macula lutea.⁵ T

his part of the eye absorbs significant amounts of blue light, which causes ionisation and damages the retina.⁷

The role of lutein and zeaxanthin is to serve as ‘sunglasses’ to absorb and filter blue light and scavenge harmful reactive oxygen species to prevent damage by significantly reducing the oxidative stress on the retina.^4,5

The best sources of lutein and zeaxanthin include dark green leafy vegetables, with the traditionally orange-yellow colour masked by the additional presence of chlorophyll.

Other good sources include pumpkin, corn, egg yolk, yellow-fleshed fruits and avocado.⁷ More recent studies have shown that lutein and zeaxanthin become more bioavailable when consumed with fat, making avocado and eggs quality choices.^5,3

Antioxidants: vitamin C and vitamin E

Accordingly, other beneficial vitamins include the antioxidant vitamins: vitamin C and vitamin E, which are found in ample amounts in the retina and have been shown to protect eye tissue from unstable free radicals.^3,5

As well as acting as an antioxidant itself, vitamin C helps vitamin E return to its slightly more potent antioxidant state.³

Vitamin C is rich in citrus fruit and berries, while Vitamin E is predominantly found in nuts, avocados and vegetable oils.⁵

Polyunsaturated fat: omega-3

Given the rich polyunsaturated fatty acid concentration within eye tissue⁶, it is no surprise that omega-3 should be recommended as a core dietary item for customers interested in their eye health.²

Some recent research suggests that eye disease occurs less frequently in people with a higher consumption of fish.²

Omega-3s can be found in fish and some nut and vegetable oils.⁵

So, can diet play a role in eye health?

Yes. Nutrition is a powerful form of preventative medicine — people should be encouraged to care for their eye health and be advised to choose foods, or proper dietary supplements, that provide these key micronutrients.

References

1. Pinazo-Durán MD, Gallego-Pinazo R, García-Medina JJ, et al. Oxidative stress and its downstream signaling in aging eyes. Clin Interv Aging. 2014;9:637–652
2. Kohn J. Are there nutrients that support eye health? Chicago. Journal of the Academy of Nutrition and Dietetics: 2015;115(9);1548.
3. Lien EL et al Nutritional influences on visual development and function. Prog Retin Eye Res. 2011 May;30(3):188–203.
4. El-Sayed M, Abdel-Aal E-SM, Humayoun A, Zaheer K, et al. Dietary Sources of Lutein and Zeaxanthin Carotenoids and Their Role in Eye Health. Nutrients. 2013(5):1169–1185.
5. Kondrot E. Eye Health and Nutrition: Why Healthy Foods are Important. Healing the eye. 2017. Accessed at www.healingtheeye.com
6. Rasmussen H & Johnson E. Nutrients for the aging eye. Clin Interv Aging. 2013(8):741–748.
7. Szalay J. What are carotenoids. Live Science. 2015. Accessed at www.livescience.com