It has been proposed that antioxidants may prevent cellular damage in the retina by reacting with free radicals that are produced in the process of light absorption.
The objective of this review was to assess the effects of antioxidant vitamin or mineral supplementation, or both, on the progression of age-related macular degeneration (AMD).
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (2005, Issue 4); MEDLINE (1966 to January 2006); SIGLE (1980 to March 2005); EMBASE (1980 to January 2005); NRR (2005, Issue 4); AMED (1985 to January 2006); and PubMed (24 January 2006 covering last 60 days), reference lists of identified reports and the Science Citation Index. We contacted investigators and experts in the field for details of unpublished studies.
We included randomised trials comparing antioxidant vitamin or mineral supplemention (alone or in combination) to a control intervention in people with AMD.
The author extracted data and assessed trial quality. Where appropriate, data were pooled using a random-effects model unless three or fewer trials were available in which case a fixed-effects model was used.
Eight trials were included in this review. The majority of people were randomised in one trial (AREDS in the USA) that found a beneficial effect of antioxidant (beta-carotene, vitamin C and vitamin E) and zinc supplementation on progression to advanced AMD (adjusted odds ratio 0.68, 99% confidence interval 0.49 to 0.93). People taking supplements were less likely to lose 15 or more letters of visual acuity (adjusted odds ratio 0.77, 99% confidence interval 0.58 to 1.03). Hospitalisation for genito-urinary problems was more common in people taking zinc and yellowing of skin was more common in people taking antioxidants. The other trials were, in general, small and the results were inconsistent.