Antioxidants, Vitamins, Carotenoids and Eye Health
Rautiainen and colleagues report that eating a diet rich in antioxidants is associated with reduced risk of age-related cataracts. Colorful fruit and vegetables, whole grain cereals, teas and spices are good sources of antioxidants. Why are antioxidants important for eye health?
The retina of the eye consists of light-sensitive cells. These cells turn light into electric signals that are transmitted to the brain. Retinal cells have a lipid bilayer, rich in the long chain polyunsaturated fatty acid (LCPUFA) docosahexaenoic acid (DHA). DHA contributes to membrane integrity, visual signaling pathways, and modulates inflammatory processes. However, LCPUFA are easily oxidized by free radicals which are generated when light, especially blue light, strikes the retina. Antioxidants, like vitamins A, C, E and the pro-vitamin A form known as beta-carotene, help quench free radicals. The retina also has high concentrations of two carotenoids, lutein and zeaxanthin. By co-localization of antioxidant micronutrients with LCPUF, the lipid bilayer is protected from oxidative damage. Since light in effect damages the retina, it is reasonable to expect that a diet rich in antioxidants would be beneficial.
Rautiainen and colleagues find evidence confirming this relationship. They assessed the total antioxidant capacity (TAC) of the diet of 30,607 women (49-83y) who participated in the prospective Swedish Mammography Cohort study for an average of 7.7y. During this time, participants completed dietary intake surveys which were mated with a food database of TAC values. At best this approach provides a crude measure of nutrient status. However, in a large group of participants where some make healthier dietary choices, i.e. foods with high TAC values, and others don’t, a statistically significant correlation was observed.
The Age-Related Eye Disease Study (AREDS) and its followup (AREDS2) are the largest randomized, controlled trials (RCTs) to determine the effect of antioxidant nutrients on eye disease. From AREDS, it was learned that supplementing with vitamin C, vitamin E, beta-carotene, zinc and copper reduced the 5y risk of developing age-related macular disease (AMD) 25% and risk reduction increased to 34% by 10y. . After 10y, the risk reduction was 34%. Participants using AREDS2 formulations had the same risk of progression to advanced AMD as those using the original AREDS formulation. In a secondary analysis, the addition of lutein and zeaxanthin yielded a 10% reduction in risk of progressing to advanced AMD.
Bottomline is this: When our bodies do not have an adequate supply of antioxidant vitamins and carotenoids, there can be health consequences. To guide your choices, visit the USDA National Nutrient Database or the NIH Office for Dietary Supplements website.
Rautiainen S, Lindlad BE, Morgenstern R, Wolk A. Total antioxidant capacity of the diet and risk of age-related cataract: A population-based prospective cohort of women. 2014 JAMA Opthalmal doi: 10.1001/jamaopthalmol.2013.6241
Carlsen MH, Halvorsen BL, Holte K, Bohn SK, Dragland S, Sampson L, Willey C, Senoo H, Umezono Y, Sanada C, Barikmo I, Berhe N, Willett WC, Phillips KM, Jacobs Jr DR, Blomhoff R. The total antioxidant content of more than 3100 foods, beverages, spices, herbs and supplements used worldwide. 2010 Nutr J http://www.nutritionj.com/content/9/1/3
Querques G, Souied EHC. The role of omega-3 and micronutrients in age-related degeneration. 2014 Survey of Opthalmol doi:10.1016/j.survopthal.2014.01.001
Chew EY, Clemons TE, Agron E, Sperduto RD, San Giovanni JP, Kurinji N, Davis MD. Long-term effects of vitamins C and E, β-caroten, and zinc on age-related macular degeneration. 2013 Opthalmol doi:10.1016/j.optha.2013.01.021
The Age-Related Eye Disease Study2 (AREDS2) Research Group. Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: The Age-Related Eye Disease Study 2 (AREDS2) randomized clinical trial. 2013 JAMA doi:10.001/jama.2013.4997
The Age-Related Eye Disease Study2 (AREDS2) Research Group. Secondary analyses of the effects of lutein/zeaxanthin on age-related macular degeneration progression. AREDS2 Report No 3. 2014 JAMA Opthalmol doi:10.1001/jamaopthalmol.2013.7376