Zinc and antioxidants slow progression of macular degeneration – Literature Review & Commentary
Alan R. Gaby
Some 3,640 individuals (aged 55-80 years) with age-related macular degeneration (AMD) were randomly assigned to receive, in double-blind fashion, daily tablets containing: 1) antioxidants (vitamin C 500 mg; vitamin E 400 IU; and beta-carotene 15 mg); 2) zinc 80 mg (as zinc oxide), balanced with copper 2 mg; 3) antioxidants plus zinc; or 4) placebo. During a mean follow-up period of 6.3 years, compared with the placebo group, there was a significant 28% reduction in the risk of developing advanced AMD in the antioxidants-plus-zinc group (odds ratio [OR] = 0.72; 99% CI, 0.52-0.98). The ORs for zinc alone and antioxidants alone were 0.75 (99% CI, 0.55-1.03) and 0.80 (99% CI, 0.59-1.09), respectively. When the analysis was restricted to individuals with more severe disease at baseline, the effects were more pronounced (antioxidants plus zinc: OR 0.66; 99% CI, 0.47-0.91; zinc: OR = 0.71; 99% CI, 0.52-0.99; antioxidants: OR 0.76; 99% CI, 0.55-1.05). Both zinc and antioxidants plus zinc significantly reduced the odd s of developing advanced AMD in this higher-risk group. The only statistically significant reduction in incidence of at least moderate visual acuity loss (15 letters or more) occurred in the antioxidants-plus-zinc group (OR 0.73; 99% CI, 0.54-0.99). No significant adverse effects were seen.
Comment: The results of this double-blind study indicate that supplementation with antioxidants plus zinc significantly reduced the progression of AMD, and that for patients with more advanced disease, both zinc alone and antioxidants plus zinc reduced the progression. In addition, antioxidants plus zinc significantly reduced the incidence of visual loss in the group as a whole. This study confirms a previous report showing that zinc supplementation can slow the progression of AMD. The results of the new study may have been even more pronounced if a form of zinc other than zinc oxide had been used. Zinc oxide is not as well absorbed as other zinc salts, although it is a reasonably good sunscreen.
Age-Related Eye Disease Study Research Group. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8. Arch Ophthalmol 2001;119:1417-1436.
COPYRIGHT 2002 The Townsend Letter Group
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