Antioxidant vitamin and mineral supplements for preventing age-related macular degeneration

 

Abstract

Background

Some observational studies have suggested that people who eat a diet rich in antioxidant vitamins (carotenoids, vitamins C and E) or minerals (selenium and zinc) may be less likely to develop age-related macular degeneration (AMD).

Objectives

The aim of this review was to examine the evidence as to whether or not taking vitamin or mineral supplements prevents the development of AMD.

Search strategy

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) in The Cochrane Library (2005, Issue 4), MEDLINE (1966 to January 2006, week 3), SIGLE (1980 to 2005/03), EMBASE (1980 to 2006, week 3), National Research Register (2005, Issue 4), AMED (1985 to January 2006) and PubMed (on 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 We contacted investigators and experts in the field for details of unpublished studies.

Selection criteria

We included all randomised trials comparing an antioxidant vitamin and/or mineral supplement (alone or in combination) to control. We included only studies where supplementation had been given for at least one year.

Data collection and analysis

Both review authors independently extracted data and assessed trial quality. No data synthesis was conducted.

Main results

Three randomised controlled trials were included in this review. One trial in Finnish men randomised participants to placebo, vitamin E, beta-carotene or both. The second trial in Australia randomised participants to vitamin E or placebo. The third trial based in USA randomised participants to antioxidant vitamins or zinc, using placebo as a control group. There was no statistically significant association with treatment. Although the number of people randomised into these three trials is large, as new cases of AMD occur infrequently in the general population, the number of cases was small (n = 23). Thus, in spite of these studies being large, they were underpowered to examine this question. However, none of the studies indicated an effect on potential early signs of the condition i.e. early ARM.

Authors' conclusions

There is no evidence to date that the general population should take antioxidant vitamin and mineral supplements to prevent or delay the onset of AMD. There are several large ongoing trials. People with AMD should see the related Cochrane review "Antioxidant vitamin and mineral supplements for slowing the progression of age-related macular degeneration".

 

Synopsis

Plain language summary

Antioxidant vitamins and mineral supplements to prevent the development of age-related macular degeneration

Age-related macular degeneration (AMD) is a condition affecting the central area of the retina (back of the eye). The retina can deteriorate with age and some people get lesions that can lead to loss of central vision. Some studies have suggested that people who eat a diet rich in antioxidant vitamins (carotenoids, vitamins C and E) or minerals (selenium and zinc) may be less likely to get AMD. The authors identified three large, high quality randomised controlled trials based in Australia, Finland and USA. One trial in Finnish men randomised participants to placebo, vitamin E, beta-carotene or both. The Australian trial compared participants to vitamin E or placebo and the American study randomised participants to antioxidants or zinc using placebo as the control. This review found no evidence that people in the general population should take antioxidant vitamin or mineral supplements to reduce their risk of AMD. The results of ongoing trials are awaited.