Macular degeneration, or age-related macular degeneration (AMD), is a leading cause of vision loss in Americans 60 and older. It is a disease that destroys your sharp, central vision. You need central vision to see objects clearly and to do tasks such as reading and driving.
AMD affects the macula, the part of the eye that allows you to see fine detail. It does not hurt, but it causes cells in the macula to die. In some cases, AMD advances so slowly that people notice little change in their vision. In others, the disease progresses faster and may lead to a loss of vision in both eyes. Regular comprehensive eye exams can detect macular degeneration before the disease causes vision loss. While treatment can slow vision loss, it does not restore vision. AMD is the most common cause of vision loss in developed countries.
This week, I discussed several studies (on my facebook page) which looked at macular degeneration. In summary, the studies I discussed concluded that you may reduce your risk of developing macular degeneration by doing the following:
* Supplementating daily with the two nutrients known as lutein and zeaxanthin
* Protecting the eyes from sunlight exposure (using hats or protective sunglasses) AND consuming high levels of dietary antioxidants such as vitamin C, vitamin E, zeaxanthin, and zinc
* Eating foods (carbohydrates) which have a low glycemic index (such as oatmeal)
While I only discussed one study detailing the benefits of lutein and zeaxanthin in reducing the risk of AMD, I want to call attention to the fact that numerous studies have pointed to the importance of lutein and zeaxanthin in maintaining eye health.
A separate study published in the September 2007 issue of the journal Archives of Ophthalmology provides more evidence that zeaxanthin and lutein may protect against AMD. In this report, members of the Age-Related Eye Disease Study (AREDS) Research Group evaluated the diets of 4,519 AREDS participants aged 60 to 80 years. Retinal photographs were used to divide the subjects into five categories of macular disease severity, from individuals with little or no evidence of macular degeneration (the control group) to severe, neovascular disease. Dietary questionnaires were analyzed for lutein, zeaxanthin, beta- carotene, lycopene, and other nutrient levels. Participants whose intake of lutein and zeaxanthin were greatest had a significantly lower risk of AMD than those whose intake was least, and were less likely to have large or extensive intermediate drusen, the deposits on the retina or optic nerve that characterize the disease. No risk reductions were associated with the other nutrients examined in this study.
In yet another study conducted at the University of Georgia in 2008, lutein and zeaxanthin were found to improve eye health by reducing the harmful effects of glare on a test group of people with normal eyesight. Healthy subjects with an average age of 23.9 were assigned to receive daily supplements of lutein (10 mg) and zeaxanthin (2 mg) for six months. The subjects' eyes were then tested for the effects of glare as experienced in everyday situations, including being outdoors on bright days, lengthy sessions of looking at a computer monitor, and nighttime exposure to oncoming headlights. Following six months of supplementation, the participant's average macular pigment optical density (MPOD) increased significantly from the average value at the beginning of the study. MPOD is a measure of the eye's ability to filter short-wave light. After testing the subjects for their performance in visual tasks following glare, researchers concluded that four to six months of supplementation with lutein and zeaxanthin significantly reduced the detrimental effects of the exposure and improved visual performance.
Before I move on to a couple of other studies, I want to talk some more about the nutrients lutein and zeaxanthin. Lutein is located in the central area of the human retina (known as the macula), and it is the predominant nutrient in the periphery of the macula. Zeaxanthin is concentrated more in the center. While the roles lutein and zeaxanthin play in the physiology of the eye are not completely understood, the links between lutein and eye health are so strong that several national and regional health organizations have recommended increasing dietary lutein intake. To maintain eye health, both lutein and zeaxanthin help screen out high-energy light, protecting underlying tissues from photo-induced damage. They also act as antioxidants, helping to protect the macula from damage due to oxidative stress. Both functions, as have been shown in studies, can help reduce the risk of age-related eye disease.
So where do we get lutein and zeaxinthin? They are found together in many food sources. Dark green leafy vegetables are the primary source, but they are also present in lesser amounts in other colorful fruits and vegetables, including broccoli, orange peppers, corn, peas, persimmons, and tangerines. Unfortunately, most dietary surveys indicate that few people consume optimal amounts of lutein and zeaxanthin-rich foods. In fact, average dietary intake in the U.S. is only 2 mg/day, far below the 6 mg/day level most studies indicate as a minimum needed to reduce the risk of AMD. This is where a supplement can fill in the missing gap, and is indeed the reason supplements, like multivitamins, are necessary. They fill in the missing gap. They do not replace a healthy diet. They add to, or supplement, a healthy diet.
Numerous studies are also concluding that you may reduce your risk of developing macular degeneration by eating fish, or supplementing with omega-3 fatty acids.
As evidence to that, a study was conducted in 2008 involving lutein and DHA (Docosahexanoic acid - an omega-3 fatty acid found in the retina of the eye). It was shown that both may help prevent macular degeneration. The study was conducted at Tufts University in Boston. In the study, researchers randomly assigned 49 women (between 60 and 80 years old) to one of four groups: placebo, DHA (800 mg/d), lutein (12 mg/d), or a combination lutein + DHA supplement. The objective of this four month study was to determine the effects of lutein and DHA on the women's serum concentrations and macular pigment optical density (MPOD). In all supplement groups, blood nutrient levels were higher at two and four months than at the beginning of the study. DHA supplementation resulted in central increases of macular pigment density, while lutein was associated with eccentric, or away from the center, increases. It was then concluded that supplementing lutein and DHA may help reduce the risk of age-related macular degeneration by increasing MPOD, helping protect the macula from oxidative damage, and increasing lutein transport into the macula.
In another study conducted in 2008, it was determined that eating one portion per week of fish rich in omega-3 fatty acids may reduce the risk of age-related macular degeneration (AMD) by over 50%. Fish intake is the major source of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). So that you are clear on AMD, there are actually two types: wet AMD and dry AMD. Of these two types, wet AMD is the primary cause of vision loss. In this particular study, which was published in the American Journal of Clinical Nutrition, researchers recruited 105 people (age 65 and over) with wet AMD and 2170 healthy people to act as controls, then compared their dietary habits using questionnaires. The scientists then investigated the association of oily fish and dietary DHA and EPA with wet AMD. Compared to people who consumed less than one portion of fish per week, participants who consumed at least one serving of oily fish per week had a 50% reduction in risk of developing wet AMD. In addition, people who got at least 300 mg per day of DHA and EPA were 68 and 71% less likely to have wet AMD than those with lower consumptions. The results of this study support previous research indicating a protective benefit of omega-3s against the onset of AMD. The benefit may be due in part to their important role in the layer of nerve cells in the retina.
And in two other studies published in the May 2007 Archives of Ophthalmology, it was shown that vitamin D and the omega-3 fatty acids from fish may help lower the risk of developing AMD. In the first study, researchers evaluated habitual nutrient intake through food frequency questionnaires of over 4,500 people between ages 60 and 80 who participated in a study by the National Institute of Health's National Eye Institute. Researchers found that higher dietary intakes of omega-3 long-chain polyunsaturated fatty acids, mainly from fatty fish, reduced the risk of age-related macular degeneration. The researchers speculate that these fatty acids may help promote cell health and survival as well as improve blood vessel function. In the second study, researchers evaluated serum vitamin D and early and advanced macular degeneration in over 7,752 individuals from the National Health and Nutrition Examination Survey III (NHANES III). Researchers noted that vitamin D intake was associated with a reduced risk of developing poor visual health that can lead to blindness. Participants were split into five groups based on the level of vitamin D in their blood. Those with the highest level had a 40% reduced risk of developing poor visual health compared with those with the lowest amount of vitamin D in their blood. These results support the idea that lower serum vitamin D levels may lead to progression of chronic diseases, specifically those associated with inflammation. This may be important to the health of older Americans who have a higher risk of insufficient vitamin D intake, the researchers said. While these results are promising, researchers caution that at this time there is insufficient epidemiologic evidence of the relationship between vitamin D and age-related macular degeneration to make recommendations regarding optimum vitamin D levels and fish intake to protect against the eye disease or its progression. These results warrant additional investigation to further confirm the role of omega-3 long-chain polyunsaturated fatty acids and vitamin D in AMD.
I know I presented an extensive list of studies, but I did so to make the point that there is strong evidence that you may reduce your risk of developing macular degeneration. These studies indicate that you can reduce your risk by:
(1) Supplementating daily with the two nutrients known as lutein and zeaxanthin;
(2) Protecting the eyes from sunlight exposure (using hats or protective sunglasses) AND consuming high levels of dietary antioxidants such as vitamin C, vitamin E, zeaxanthin, and zinc
(3) Eating foods (carbohydrates) which have a low glycemic index (such as oatmeal); and
(4) Eating fish, or supplementating with omega-3 fatty acids
SOURCES:
The Relationship of Dietary Lipid Intake and Age-Related Macular Degeneration in a Case-Control Study: AREDS Report No. 20. Archives of Ophthalmology. 2007 May;125(5):671-9.
Association Between Vitamin D and Age-Related Macular Degeneration in the Third National Health and Nutrition Examination Survey, 1988 Through 1994. Archives of Ophthalmology. 2007 May;125(5):661-669.
The Relationship of Dietary Carotenoid and Vitamin A, E, and C Intake With Age- Related Macular Degeneration in a Case-Control Study: AREDS Report No. 22. Age-Related Eye Disease Study Research Group. Archives of Ophthalmology. 2007;125:1225-1232.
American Journal of Clinical Nutrition, Vol. 87, No. 5, 1521-1529, May 2008
American Journal of Clinical Nutrition, Vol. 88, No. 2, 398-406, August 2008
Optometry & Vision Science 2008 Feb;85(2):82-8
American Journal of Clinical Nutrition, Vol. 88, No. 4, 1104-1110, October 2008
Neelam K, Hogg Re, et al. Carotenoids and co-antioxidants in age-related maculopathy. Ophthalmic Epidemiology. 2008 Nov-Dec;15(6):389-401..
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