Your Eyes: Health Benefits of a Plant-based Diet

Diet, Health / By Keyvan Golestaneh / November 27, 2014 January 12, 2022

Several studies in the past few years have shown that a diet high in fruits and vegetables can help alleviate many of the vision problems associated with aging. Most recently, a study by researchers in the department of Clinical Medicine at the University of Oxford in England found that people with a vegetarian or vegan diet were 30-40 percent less likely develop cataracts than people with diets high in meat (“Vegetarian diet linked to lower cataract risk,” 2011). Cataract, a change in the proteins that make up the lens of the eye and results in cloudy or blurred vision, is one of the most common eye conditions that can come up with age, with over half of Americans experiencing cataracts by the time they are 80 years old (“Facts about cataracts,” 2011).

While this most recent study does not prove meat-eating can cause cataracts, it does support previous research that links specific nutrients found primarily in plants, such as antioxidants, to a lower risk of cataracts (Christen, Liu, Glynn, Gaziano, & Buring, 2008). It also supports another earlier study that found that women who ate diets rich in many different vitamins and minerals had a lower risk of cataracts (Mares et al., 2010). A plant-rich diet may decrease the risk for cataracts by lowering the chances for oxidative stress either directly, or by reducing systemic inflammation. Systemic inflammation can in turn lead to oxidative stress. Oxidative stress hastens tissue deterioration and is one of the major causes of the diseases of older age.

An adequate or high level of lutein or zeaxanthin, vitamins C and/or E and omega-3 fatty acids have consistently been associated with a lower risk of cataracts (Mares et al., 2010). These nutrients have also been associated with a decreased risk of glaucoma (Coleman et al., 2008) and age-related macular degeneration (or maculopathy) (Chiu, Klein, Milton, Gensler, & Taylor, 2011). Glaucoma indicates a group of diseases where the pressure inside the eye increases and gradually damages vision, and macular degeneration is a condition where the retina is damaged either through abnormal growth or by degenerating cells. Both conditions are common in older people and are clearly affected by diet.

Whole foods are the best source of all these nutrients and a balanced vegetarian diet rich in plants and whole grains is the most likely to create the best support for vision health. Green leafy vegetables are a great source of lutein and orange peppers, orange juice, squash, zucchini, and corn are high in both lutein and xanthin (Sommerburg, Keunen, Bird, & van Kuijk, 1998). High levels of Vitamins A, C and E are found in apples, oranges, squash, and green leafy vegetables. Keep in mind, however, that a healthy diet is not determined through individual nutrients, but through the combination of foods that lead to the best absorption of all nutrients. Eating a lot of squash and nothing else will not ultimately support your vision or your general health.

Meat consumption may also affect how vision develops with age. There is evidence that eating meat can create an acidic environment in the body, which may also contribute to the higher oxidative stress and inflammation that can lead to cataracts and macular degeneration. The opposite of an acid is a base, or alkaline substance, and the kidneys function to restore acid-alkaline balance in the body. As we age the kidneys, like other organs, function less efficiently. As the modern American diet tends to create an acidic environment in the body, disrupting the acid-alkaline homeostasis that encourages the best kidney functioning, many health practitioners advocate pursuing a more alkaline diet. Fish, meat, poultry, shellfish, cheese, milk, and salt all induce an acidic environment, while plant consumption will be more likely to induce an alkaline environment.

There is a hypothesis that meat and milk from mammals may also be a source of inflammation due to the presence of N-glycolylneuraminic acid (Neu5Gc) (Padler-Karavani et al., 2008). This form of sialic acid is present in all mammals except humans, and there has been evidence that Neu5Gc, seen as foreign by the human immune system, activates antibody production and other immune reactions (Hedlund, Padler-Karavani, Varki, & Varki, 2008). If this is true, then consuming other mammals may trigger a chronic immune reaction, resulting in chronic inflammation.

For vegetarians and especially vegans, a balanced diet is essential. A vegan diet is very rich in concentrated plant foods, but can be low in omega-3 fatty acids and should also be supplemented with vitamin B12. For vegans and vegetarians who don’t eat eggs, the consumption of nuts and flax, chia, and hemp seeds provides an important source of some omega-3. Deficiencies in both omega-3 and vitamin B-12 can also harm vision, as well as threaten overall health.

References
Chiu, C. J., Klein, R., Milton, R. C., Gensler, G., & Taylor, A. (2009). Does eating particular diets alter the risk of age-related macular degeneration in users of the Age-Related Eye Disease Study supplements? British Journal of Ophthalmology, 93(9), 1241-1246. doi:10.1136/bjo.2008.143412

Christen, W. G., Liu, S., Glynn, R. J., Gaziano, J. M., & Buring, J. E. (2008). Dietary Carotenoids, Vitamins C and E, and Risk of Cataract in Women: A Prospective Study. Archives of Ophthalmology, 126(1), 102-109. doi:10.1001/archopht.126.1.102

Coleman, A. L., Stone, K. L., Kodjebacheva, G., Yu, F., Pedula, K. L., Ensrud, K. E., … Mangione, C.M. (2008). Glaucoma Risk and the Consumption of Fruits and Vegetables Among Older Women in the Study of Osteoporotic Fractures. American Journal of Ophthalmology, 145(6), 1081-1089. doi:10.1016/j.ajo.2008.01.022

“Facts about cataracts” (2011). National Eye Institute. Retrieved from http://www.nei.nih.gov/health/cataract/cataract_facts.asp

Hedlund, M., Padler-Karavani, V., Varki, N. M., & Varki, A. (2008). Evidence for a human-specific mechanism for diet and antibody-mediated inflammation in carcinoma progression. Proceedings of the National Academy of Sciences, 105(48), 18936-18941. doi:10.1073/pnas.0803943105

Mares, J. A., Voland, R., Adler, R., Tinker, L., Millen, A. E., Moeller, S. M., … Sarto, G.E. (2010). Healthy diets and the subsequent prevalence of nuclear cataract in women. Archives of Ophthalmology, 128(6), 738-749. doi:10.1001/archophthalmol.2010.84

Padler-Karavani, V., Yu, H., Cao, H., Chokhawala, H., Karp, F., Varki, N., … Varki, A. (2008). Diversity in specificity, abundance, and composition of anti-Neu5Gc antibodies in normal humans: Potential implications for disease. Glycobiology, 18(10), 818-830. doi:10.1093/glycob/cwn072

Sommerburg, O., Keunen, J. E., Bird, A. C., & van Kuijk, F. J. (1998). Fruits and vegetables that are sources for lutein and zeaxanthin: the macular pigment in human eyes. The British Journal of Ophthalmology, 82(8), 907-910. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/9828775

“Vegetarian diet linked to lower cataract risk” (2011). Reuters US Online Report Health News. Retrieved from http://eyesightandeyehealth.com/cataracts/vegetarian-diet-linked-cataract-risk-4765399a