Ocular Health Influenced, Maintained by Nutritional Decisions

Few individuals sit in their optometrist’s exam chair expecting to receive a nutritional education. Patients are often told that poor ocular health and vision are merely the result of genetics and factors outside of their control. Although science can substantiate the role genetics play in ocular health, research also shows that maintaining a healthy diet may protect eyes from ocular pathologies. In particular, 3 carotenoids (lutein, zeaxanthin, and meso-zeaxanthin) are essential for maintaining healthy eyesight.¹ Ultimately, patients may lower their risk of developing age-related macular degeneration (AMD) later in life and even help protect eyes from the potential effects of blue light by developing a few healthy habits.¹

Sharing the findings of researchers, both within the ophthalmic literature and from other specialties, can help patients at risk for AMD create a menu that keeps their vision and ocular health in good standing. 

Sources of Carotenoids

Lutein and zeaxanthin are responsible for the natural green or orange hues found in foods. Dark leafy greens, peas, summer squash, pumpkin, brussels sprouts, broccoli, asparagus, lettuce, carrots, and pistachios are among the foods high in lutein and zeaxanthin.²

One of the best natural food sources of lutein and zeaxanthin is cooked spinach. Spinach has a high concentration of these important nutrients that contribute to eye health and and cognition.² The high lutein concentration in spinach protects vision by filtering out potentially damaging blue light wavelengths.¹

Spinach also contains antioxidants, such as beta-carotene, that help prevent free radical damage to cells. Free radicals are unstable molecules that can cause damage to the body’s cells. They can contribute to heart disease progression, cancer growth, and aging. Carotenoids protect against free radical damage, defending multiple systems within the body, including the eyes.^1,2

Function of Carotenoids 

Carotenoids protect against a variety of diseases by reducing oxidative stress. Oxidative stress is caused by reactive oxygen species (ROS), which are generated by cellular metabolism and environmental factors such as pollution and ultraviolet light exposure. When ROS accumulate in the body, they can damage DNA and proteins within the cells. This leads to inflammation and other diseases such as Alzheimer disease or AMD.

A third carotenoid has been found in the macula, according to a study.¹ This pigment, known as meso-zeaxanthin, is not commonly found in dietary sources and seems to be produced in the retina from ingested lutein.

Ocular Benefits of Lutein and Zeaxanthin

Researchers believe that lutein, zeaxanthin, and meso-zeaxanthin in the macula block blue light from reaching the underlying structures in the retina, thereby reducing the risk of light-induced oxidative damage that can lead to AMD.³

One investigation revealed that a nutritional supplement containing meso-zeaxanthin, lutein and zeaxanthin increased the optical density of the macular pigment in a majority of participants.⁴ The macular pigment is believed to offer protection against the development of macular degeneration. Another study confirmed the protective effects of consuming higher levels of lutein and zeaxanthin in the diet and found that increasing their intake was associated with a lower incidence of AMD.⁵

The Dark Side of Blue Light

Natural sunlight, which is a form of blue light, can help improve mood, heighten attention, and increase reaction times, according to research. Spending 30 minutes in the morning sun may help reduce stress, strengthen the immune system, combat depression, and increase vitamin D and nitric oxide, which protect the heart and vascular system.⁶ But additional studies show that modern habits are overwhelming eyes with blue light. 

Blue light exposure is rising as a result of the widespread use of gadgets with screens, particularly after sunset. Technology and indoor life not only put individuals at a higher risk for myopia and consequential effects such as degenerative eye diseases — science is also revealing that the accompanying blue light is destructive to overall health, as well. ⁷ 

The human eye is only equipped with defenses against some types of light. Unfortunately, it does not keep out blue light. And people are being exposed at an alarming rate due to an increased use of digital screens and devices.

Research suggests that increasing carotenoid intake through fruits and vegetables, may help protect eyes from the harmful effects of blue light.^1,2 And more blue light exposure increases the risk of developing macular degeneration. Although the term “age-related macular degeneration” implies that age alone is responsible for central vision deterioration, younger people who are exposed to blue light from cellphones and computer screens for extended periods of time can develop symptomatology similar to patients with AMD.

Limiting exposure to blue light by wearing lenses with blue light-blocking filters or downloading apps to block incoming blue light can be instrumental in protecting the eyes from the harmful effects of blue light. However, the protective effect of consuming a diet rich in carotenoids should not be underestimated. 

Age-Related Macular Degeneration

Regularly scheduled eye exams and a healthy diet can help to mitigate the potentially harmful effects of AMD. This disease risk must not be taken lightly considering it is “the leading cause of irreversible vision loss and blindness in developed nations.” ⁸ AMD also has one of the highest rates of progression among diseases, with 78% of these patients experiencing irreversible vision loss by the time they seek treatment. In many cases, prevention is possible with early diagnosis and intervention.⁹

Fortunately, steps can be taken immediately to ensure eyes stay healthy with age. Adding as little as 60 grams of spinach a day for 1 month can significantly boost macular pigment in most people.² 

Research shows that those who consume more lutein and zeaxanthin have a lower risk of developing advanced AMD.¹ Another study confirms the importance of diet in combating AMD, stating “displacing foods of modern commerce (processed foods) are the primary and proximate cause of AMD. Any ancestral diet rich in fat soluble nutrients and minerals will prevent and may treat AMD.”⁶

The Age-Related Eye Disease Study (AREDS1; ClinicalTrials.com Identifier: NCT00000145), showed that certain micronutrients (beta carotene, vitamin C, vitamin E, zinc oxide, and cupric oxide) can reduce the risk of progression from intermediate AMD to the advanced stage by 25%.

The Emerging Field of Health and Wellness for Optometry  

The eyes  can reveal the secrets of hidden health concerns, as clinicians can see into them and learn about their patients’ anatomy.

Eyes need nutrients to function properly and stay healthy. Carotenoids are among the nutrients needed for optimal health. Lutein, zeaxanthin and meso-zexanthin are carotenoids that eyes require to function normally. Getting these nutrients through a diet is preferable to taking supplements. However, modern farming practices have diminished the nutrient content of many fruits and vegetables over the last 50 years, making supplementation necessary in many cases.¹⁰ 

I typically recommend a comprehensive supplement that contains 10mg of lutein, 10 mg of meso-zexanthin, and 2mg of zeaxanthin. Choosing the supplement route should involve using a reputable company that clearly lists all ingredients. Failure to consume adequate levels of these antioxidants may result in ocular damage over time.

References

1. Abdel-Aal E-SM, Akhtar J, Zaheer K, Ali R. Dietary sources of lutein and zeaxanthin carotenoids and their role in eye health. Nutrients. 2013;5(4):1169-1185. doi:10.3390/nu5041169 
2. Gregor M. Do lutein supplements help with brain function? NutritionFacts.org. https://nutritionfacts.org/video/do-lutein-supplements-help-with-brain-function. Updated December 31, 2018. Accessed July 20, 2022.
3. Kattouf V. Macular degeneration: types, causes, symptoms and treatments. All About Vision. https://www.allaboutvision.com/conditions/amd.htm. Updated June 14, 2022. Accessed July 20, 2022.
4. Bone RA, Landrum JT, Cao Y, Howard AN, Alvarez-Calderon F. Macular pigment response to a supplement containing meso-zeaxanthin, lutein and zeaxanthin. Nutr Metab (Lond). 2007;4:12. doi:10.1186/1743-7075-4-12
5. Marse-Perlman, Fisher AI, Klein R, et al. Lutein and zeaxanthin in the diet and serum and their relation to age-related maculopathy in the third national health and nutrition examination survey. Am J Epidemiol. 2001;153(5):424-432. doi:10.1093/aje/153.5.424
6. Mead MN. Benefits of sunlight: a bright spot for human health. Environ Health Perspect. 2008;116(4):A 160-7. doi:10.1289/ehp.116-a160
7. Zin-Chun Z, Zhou Y, Tan G, Li J. Research progress about the effect and prevention of blue light. Int J Ophthalmol. 2018;11(12):1999-2003. doi:10.1824O/ijo.2018.12-20
8. Knobbe CA, Stojanoska M. The ‘displacing foods of modern commerce’ are the primary and proximate cause of age-related macular degeneration: a unifying singular hypothesis. Med Hypotheses. 2017;109:184-198. doi:10.1016/j.mehy.2017.10.010
9. Cervantes-Castañeda RA, Banin E, Hemo I, Shpigel M, Averbukh E, Chowers I. Lack of benefit of early awareness to age-related macular degeneration. Eye (Lond). 2007;22(6):777-781. doi:10.1038/sj.eye.6702691
10. Hammond BR Jr, Renzi LM. Carotenoids. Adv Nutr. 2013;4(4):474-476. doi:10.3945/an.113.004028