Antioxidant supplements to prevent or slow down the progression of AMD: a systematic review and meta-analysis.

INTRODUCTION: The aim of this review was to examine the evidence as to whether antioxidant vitamin or mineral supplements prevent the development of AMD or slow down its progression. METHODS: Randomised trials comparing antioxidant vitamin and/or mineral supplement to control were identified by systematic electronic searches (updated August 2007) and contact with investigators. Data were pooled after investigating clinical and statistical heterogeneity. RESULTS: There was no evidence that antioxidant (vitamin E or beta-carotene) supplementation prevented AMD. A total of 23 099 people were randomised in three trials with treatment duration of 4-12 years; pooled risk ratio=1.03 (95% CI, 0.74-1.43). There was evidence that antioxidant (beta-carotene, vitamin C, and vitamin E) and zinc supplementation slowed down the progression to advanced AMD and visual acuity loss in people with signs of the disease (adjusted odds ratio=0.68, 95% CI, 0.53-0.87 and 0.77, 95% CI, 0.62-0.96, respectively). The majority of people were randomised in one trial (AREDS, 3640 people randomised). There were seven other small trials (total randomised 525). CONCLUSIONS: Current evidence does not support the use of antioxidant vitamin supplements to prevent AMD. People with AMD, or early signs of the disease, may experience some benefit from taking supplements as used in the AREDS trial. Potential harms of high-dose antioxidant supplementation must be considered. These may include an increased risk of lung cancer in smokers (beta-carotene), heart failure in people with vascular disease or diabetes (vitamin E) and hospitalisation for genitourinary conditions (zinc).