Cataracts—an opaque buildup of damaged proteins in the lens of the eye—are the leading cause of visual decline in those over 65. In fact, most people in that age group have at least the beginnings of cataract formation. Many factors contribute to the development of cataracts, but damage by free radicals is believed to play a major role. (See the article on Atherosclerosis for a description of free radicals.)
Cataracts can be removed surgically. Although this has become a relatively quick, safe, easy, and painless surgery, it does not result in completely normal vision. Clearly, preventing cataracts, if possible, would be preferable.
Numerous observational studies suggest that high intake of antioxidants —such as vitamin C , vitamin E , and carotenoids ( beta-carotene , lutein , astaxanthin and lycopene —are associated with a reduced incidence of cataracts. 1-11,17 However, this by itself does not prove that the use of antioxidant supplements can prevent cataracts. Only double-blind, placebo-controlled studies can do that. (For information on why the double-blind design is so important, see Why Does This Database Rely on Double-blind Studies? ) Unfortunately, the results of several large studies of this type were not encouraging.
In an enormous, double-blind, placebo-controlled trail involving almost 40,000 female healthcare professionals, use of natural vitamin E at a dose of 600 mg every other day over a 10-year period failed to have any effect on cataract development. 18
In another large, 8-year trial, 11,545 physicians aged 50 years and older were randomized to four different treatment groups: vitamin E (400 units) every other day plus vitamin C (500 mg) daily, vitamin E every other day plus placebo daily, vitamin C daily plus placebo, or placebo only. 20 Neither vitamins E or C had any significant effect on preventing cataracts.
And, in a similar trial, 4,629 older people received either placebo or an antioxidant supplement containing 500 mg of vitamin C, 400 IU of vitamin E, and 15 mg of beta-carotene. The results over more than 6 years showed no effect on the risk of development of cataracts, nor the rate at which existing cataracts progressed to greater severity. 12
A 5-year double-blind, placebo-controlled study of 798 people in Southern India failed to find benefit with supplemental antioxidants, despite the fact that dietary antioxidant deficiency was common among the people studied. 16
In addition, a previous double-blind, placebo-controlled study examining the use of beta-carotene or vitamin E alone in male smokers failed to find the supplements effective. 13 On a more positive note, though, one large study found that beta-carotene supplements helped prevent cataracts in the subgroup of study participants who smoked. 14 However, no benefits were seen in the group as a whole. In any case, people who smoke are generally not advised to take extra beta-carotene. (For the reasons behind this concern, see the Beta-carotene article.)
In another long-term study involving over 1,000 older adults, multivitamin and minerals supplements led to a significant decrease in the development of cataracts compared to placebo over a 9-year period. However, these favorable results were tempered by an inexplicable increase in the number of a subtype of cataracts (posterior subcapsular) occurring among those taking the multivitamin/mineral supplements. 19
Herbs high in antioxidant flavonoids are frequently suggested for preventing cataracts. These include bilberry , ginkgo , OPCs , and turmeric . For various theoretical reasons, the supplements carnosine , lipoic acid , niacin (vitamin B 3 ) , riboflavin (vitamin B 2 ) , selenium , taurine , whey protein , and zinc have also been proposed. However, there is little real evidence that any of these treatments actually help.
12. Age-Related Eye Disease Study Research Group. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E and beta carotene for age-related cataract and vision loss. AREDS Report No. 9. Arch Ophthalmol. 2001;119:1439-1452.
13. Teikari JM, Rautalahti M, Haukka J, et al. Incidence of cataract operations in Finnish male smokers unaffected by alpha tocopherol or beta carotene supplements. J Epidemiol Community Health . 1998;52:468-472.
15. Olmedilla B, Granado F, Blanco I, et al. Lutein, but not alpha-tocopherol, supplementation improves visual function in patients with age-related cataracts: a 2-y double-blind, placebo-controlled pilot study. Nutrition . 2003;19:21-24.
16. Gritz DC, Srinivasan M, Smith SD, et al. The Antioxidants in Prevention of Cataracts (APC) Study: Effects of Antioxidant Supplements on Cataract Progression in South India. Br J Ophthalmol . 2006 Mar 23 [Epub ahead of print].
19. A randomized, double-masked, placebo-controlled clinical trial of multivitamin supplementation for age-related lens opacities clinical trial of nutritional supplements and age-related cataract. Report Number 3. Ophthalmology. 2008;115:599-607.e1.
Last reviewed July 2012 by EBSCO CAM Review Board
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