The Age-Related Eye Disease Study
Scientists have long been interested in whether supplemental doses of certain vitamins and minerals could affect the onset and progression of AMD and cataracts. Researchers at the National Institutes of Health examined whether nutrition supplements could protect against AMD in the Age-Related Eye Disease Study (AREDS and AREDS2).
The AREDS involved about 4,700 men and women aged 55 to 80. About 3,600 of them were diagnosed with borderline or early, intermediate, or advanced AMD in at least one eye and were followed for about six years for the AMD portion of the study. Those participants who took a supplement containing antioxidants and zinc were about 25% less likely to develop further AMD, compared to those who took a sugar pill. The supplements did not seem to have much effect on those who began the study with borderline or mild AMD, and did not affect the risk of cataract. While supplements did not reverse damage or restore vision already lost from AMD, they did appear to help stop or delay progression of the disease.
The AREDS2 trial explored whether further benefit could be found by adding lutein, zeaxanthin, or omega-3 fatty acids to the original formulation of nutritional supplements offered. They found no effect on the risk of late AMD. They did discover benefit in replacing the beta-carotene however with lutein and zeaxanthin which was found may further reduce the risk of late AMD.
The supplement that showed promise contained 500 mg of vitamin C, 400 International Units of vitamin E, 15 mg of beta-carotene, 80 mg of zinc, and 2 mg of copper. Copper must be added to the supplement to prevent copper deficiency, which can occur with high zinc intake.
Note that this is a high-dose formulation whose long-term effects, if any, are unknown. High doses of beta-carotene, such as those found in this mix, may be harmful to smokers.
The people in this study who benefited were those who already had AMD (the study was not designed to test whether supplements can prevent AMD) and whose disease had already progressed to a certain point. In other words, these supplements are only appropriate for certain people, and anyone considering their use should discuss it with their doctor first.
There is no evidence of benefits from other supplements, such as a pill containing lutein and zeaxanthin. (Lutein and zeaxanthin were not included in the AREDS study.) The jury is still out as to whether substances such as lutein and zeaxanthin are truly helpful in reducing the risk of eye disease. All that is known right now is that there is an association between eating foods high in these compounds and reduced risk. Because most studies of lutein and zeaxanthin have involved food sources of these nutrients, it is difficult to say if a supplement of these carotenoids alone would be beneficial; other nutrients in these carotenoid-rich foods might also be necessary to have an effect.