In 1998, the National Eye Institute (of the National Institutes of Health) completed a large study called the Age-Related Eye Disease Study (or AREDS). It showed that nutritional intervention in the form of supplements (Beta-carotene, vitamin C, vitamin E, zinc, and copper) can delay the progression of AMD for those at high risk for the disease. The study established that AMD is a nutrition responsive disorder.
The NEI has just initiated a second randomized placebo-controlled clinical trial, AREDS2, with over 80 participating research centers that will evaluate whether lutein and zeaxanthin as well as omega-3 fatty acids have similar protective effects against AMD and cataracts. The AREDS II study (Age Related Eye Disease Study II) aims to refine the findings of the AREDS, which showed a 25 percent reduction in risk of advanced Age-related Macular Degeneration (AMD) associated with oral supplementation with high-dose antioxidants vitamins and minerals. AREDS II plans to evaluate the role of the carotenoids 10 mg/d lutein and 2mg/d zeaxanthin, as well as 1 gram/d of n-3 fatty acids (as a combination of 2:1 EPA to DHA). The rate of disease progression will be evaluated in approximately 4000 individuals with AMD. Because previous findings showed primary efficacy in high risk AMD patients, the AREDS2 began enrolling 4000 such patients beginning in late 2006.
Eye Health & Nutrition
Science suggests that proper nutrition is critical to maintaining the health of your eyes. Many researchers and eye care practitioners believe that the daily intake of certain nutrients — zinc, lutein, zeaxanthin, vitamins C, E, (A) and essential fatty acids — may reduce the risk of certain chronic eye diseases, including age-related macular degeneration (AMD) and cataracts.
Lutein & Zeaxanthin: Carotenoids like lutein and zeaxanthin are large complex molecules found in plants. Due to their ability to efficiently absorb light, carotenoids generally serve plants by harvesting light energy or serving as pigmentation.
Lutein's role in eye-protection most likely stems from two important functions. Research suggests lutein in the eye's macula filters high-energy blue wavelengths of visible light – from both natural sunlight and indoor light – as they enter the eye. By passively absorbing high-energy blue-light, lutein limits photo-oxidative damage to tissues. Lutein also may function as an antioxidant to help protect our eyes from damage caused by unstable atoms known as free radicals, which can interact with and break down healthy tissues. Leading carotenoid researchers believe this dual role may lead to a reduced risk of AMD and cataracts, shorten glare recovery times, and lessen chromatic aberation and photophobic response.
Essential Fatty Acids (EFA's): DHA is an omega-3 fatty acid that can be converted in the human liver from alpha-linoleic acid or consumed directly in the diet from fish, fish oil, meat, or supplements. Overall, there are three primary omega 3 fatty acids in human blood and plasma: alpha-linoleic acid, eicosapentanoic acid (EPA) and docosahexanoic acid (DHA). Of these DHA is the most abundant fatty acid in plasma as well as brain and retinal cell membranes, particularly the rod outer segments. The role of DHA in visual development is well established and because of the constant renewal of photoreceptor outer segments, a constant supply of DHA may be required for proper retinal function. During analysis of the Health Professionals Follow-up study and the Nurse's Health Study there was an observed 30 percent reduction in risk of AMD in highest DHA intake quintile vs. lowest.
Lutein & Zeaxanthin
The richest sources of free lutein in a typical human diet are dark green leafy vegetables, with the highest concentration found in kale followed by spinach. The bioavailability of lutein, unlike many other nutrients, is enhanced by chopping and cooking the food. This is likely due to the disruption of the strong interaction between chlorophyll and lutein molecules.
While eggs have relatively low concentrations of lutein, they may be one of the most bioavailable sources due to the lack of chlorophyll interaction and the high lipid and cholesterol matrix in the yolk. Interestingly, chickens are fed lutein in order to increase the yellow of the yolk.
(per 1 cup)
|Turnip greens, cooked
|Corn, canned or cooked
|Green peas, canned
|Romaine lettuce, raw
|Green beans, cooked
|Egg (2 large)
|Orange (1 medium)
Essential Fatty Acids
EPA and DHA are concentrated in fatty fish and marine mammals. For individuals who choose not to consume fish, vegetarian DHA is commercially manufactured from microalgae. Animals can convert very small amounts of DHA through consumption of a-linolenic acid, an omega-3 fatty acid found in plants, animals, and milk. DHA and EPA are concentrated only in a small number of less-frequently consumed fish-based foods or through omega-3 fatty acid supplements in the form of oil or capsules.
Vitamin C is found almost exclusively in fruits and vegetables, including citrus fruits such as oranges, lemons, grapefruit and limes.
Vitamin E can be found in nuts, salad and vegetable oils, peanut butter, fortified cereals and sweet potatoes.
Good sources for zinc include red meat, seafood, poultry, eggs, wheat germ, mixed nuts, black-eyed peas, tofu, and baked beans.