The Importance of Zeaxanthin and Lutein for Eye Health
13 July 2017
Perhaps no part of anyone’s health is as obvious as vision. You may be like many people and have perfect 20/20 vision with no use of glasses or contacts to improve deficiencies. Or, you might be like other people who need corrective lenses to be able to see properly. Even worse, you could have age-related macular degeneration (AMD), other serious disorders affecting your eyesight like cataracts, or even blind. Hopefully, you have none of the latter issues, and if you are just thinking about the health of your eyes for the first time, you might want to consider what you can do through nutrition to help keep your eyes healthy and functioning properly.
The eye is the only part of the brain and central nervous system that can be seen on the outside of the body, as it is the organ that sends light signals through the optic nerve to the brain, which converts that information into what we perceive as the world around us. Just like the rest of our body, the eye is subjected to oxidative and other forms of stress, inflammation, and the damaging effects of modern society, such as chemical toxicities. The eye contains many important parts that work together to enable us to see; two of which are the macula and retina. The macula is a collection of structures that enables us to have visual acuity. AMD results in the loss of central vision, akin to a hole in the center of the visual field. The retina is the light-sensitive tissue layer on the eye that contains rods and cones for processing light information that gets sent to the brain to create the images of the world around us that we see. Retinopathy, like AMD, is a condition that affects your ability to see well and is typically due to inflammation and oxidative stress. Thus, as with all chronic conditions, your best strategy to reduce the risk of AMD and retinopathy is to consume nutrients that help to decrease factors like inflammation and stress of all types.
Zeaxanthin and lutein are two nutrients that are very important in the fight against inflammation and oxidative stress for overall health and particularly for the eyes. These compounds are part of the naturally occurring carotenoid family (over 600 of these have been identified by scientists so far). Zeaxanthin and lutein cause such plants as green leafy vegetables, oranges, and yellow fruits and vegetables to have their color, much in the same way that they cause our macula to be a yellow color as well. The macula primarily contains zeaxanthin, whereas the retina mostly is made up of lutein, and these are the only carotenoids, out of the 600 in nature, that are found in these important parts of the eye. These nutrients must be obtained from the diet from food or supplements, as our body does not have the ability to create them internally.
Lutein and zeaxanthin are the most vital macular pigments (MPs) in the eye. MPs are known to be associated with indicators of visual performance and acuity, and they also filter out blue light from the macula, thereby reducing the risk of AMD, and they have direct antioxidant and anti-inflammatory action. Because the eye has a large concentration of oxygen, it is exposed to significant oxidative stress through free radical production. Lutein and zeaxanthin are crucial for their antioxidant ability to scavenge these free radicals and to reduce the effects of resultant oxidative stress. A very recent study showed that in addition to its direct antioxidant effect, lutein indirectly activated antioxidant activity through a very important protein known as Nrf2 in retinal pigment epithelial cells, which sheds further light on how lutein actually works in the eye. In general, Nrf2 is crucial for protecting us from oxidative stress, so lutein being able to stimulate its action is exciting and confirmatory of its importance to our eye and overall health.
Due to their slight biochemical structural difference, zeaxanthin is a much more effective antioxidant than lutein. Zeaxanthin is prevalent in the most dense cone areas, where the risk of oxidative stress is highest. Additionally, lutein is more efficient at filtering, while zeaxanthin is better for inhibiting lipid peroxidation due to ultraviolet light. How lutein and zeaxanthin coalesce and are distributed in the eye is a very ordered and systematic process. Thus, zeaxanthin and lutein have several functions that synergistically enable us to have healthy eyes and hopefully prevent damaging diseases later in life.
If you are eating lots of colorful fruits and vegetables every day, then you might be getting an adequate amount of zeaxanthin and lutein to keep your eyes healthy. However, if you are like most people today, who do not eat sufficient quantities of these foods, then supplementing the diet with zeaxanthin and lutein should be considered to help meet your nutritional needs. Studies are now showing the benefits of these nutrients for eye health. Much of the known research has focused on AMD, given its prevalence in the elderly related to other eye diseases and that it is an expensive condition to treat with no certain cure. For example, it has been demonstrated in large, observational studies that the consumption of zeaxanthin and lutein are related to a decreased risk of AMD, suggesting that they are crucial for visual performance and in maintaining the health of the macula. Sponsored by the United States National Eye Institute, the age-related eye disease study 2 (AREDS2) was an extension of a prior study showing the benefits of different antioxidants on eye health. AREDS2 assessed the effects of dietary supplementation of 10 mg lutein plus 2 mg zeaxanthin and/or 1,000 mg omega-3 fatty acids from fish oil on AMD, cataracts, and moderate vision loss. Adding lutein plus zeaxanthin to the original AREDS antioxidant formula resulted in a 10% greater improvement compared to the first study in reducing the risk of progress to advanced AMD. When β-carotene was removed from the formula, the improvement was even greater (18%), which may be due to β-carotene being competitively absorbed with lutein and zeaxanthin. The study participants who got the best results from adding lutein plus zeaxanthin were those who had the lowest levels of lutein and zeaxanthin in their diet. Interestingly, the use of the omega-3 fatty acids neither improved nor diminished eye health, although other studies have generally shown that omega-3 fatty acids are beneficial.
While many resources have been devoted to the study of AMD and its relationship to lutein and zeaxanthin, other disorders, such as cataracts and dry eye syndrome, have not been studied as frequently. Nonetheless, lutein and zeaxanthin are the only carotenoids that have been found in the lens of the eye. Thus, some preliminary research suggests that they may have a role in protecting against the development of cataracts, since this condition is also rooted in oxidative stress and inflammation. The ability of lutein and zeaxanthin to deter oxidation and inflammation in the lens may help to prevent cataract development. Unfortunately, little else has been found to this point about the roles of lutein and zeaxanthin in their ability to prevent other eye disorders.
The consumption of lutein and zeaxanthin is considered safe at the studied levels of approximately 6-10 mg/day of lutein and 2 mg/day zeaxanthin. However, if you are a smoker, the AREDS1 and AREDS2 studies suggest that your risk of lung cancer may be even greater with supplementation of lutein and zeaxanthin. The mechanisms behind this effect are not understood at this time. Also, if you consume high doses of lutein and zeaxanthin, then you have a risk of your skin yellowing, since these are fat-soluble substances, but ultimately the yellow color will dissipate if you discontinue their use.
Thus, smart usage of lutein and zeaxanthin can be very beneficial for eye health, particularly if you use the amounts that have been studied quite extensively in persons with AMD. As our world population continues getting older, AMD, like many other chronic diseases, significantly contributes to our overburdened health care systems and has a crucial effect on the quality of life and independence of the elderly. Thus, ensuring an adequate daily intake of lutein and zeaxanthin may help to counteract some of these personal and societal costs associated with diseases like AMD. Using lutein and zeaxanthin together or in combination with some other antioxidants besides β-carotene may be effective for keeping your eyes healthy. Along with your supplements, remember to eat a wide variety of colorful fruits and vegetables to get the most out of these wonderful carotenoids from Mother Nature!
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