Current use of dietary supplementation in patients with age-related macular degeneration.

Background: The Age-Related Eye Disease Study (AREDS) Research Group recently reported significant reduction in the progression of certain categories of age-related macular degeneration (AMD) with the use of high-dose antioxidant and zinc supplementation. We studied the current use of dietary supplementation in our patients with AMD to determine whether dosages recommended in the AREDS were being achieved. We also evaluated the easiest and most cost-effective method to reach recommended dosages using supplements currently available in Canada.

Methods: Cross-sectional descriptive study conducted by patient survey from Feb. 1 to Mar. 31, 2002. All patients with the diagnosis of AMD were surveyed during an office visit at a retinal specialty clinic in Edmonton. The following information was collected: demographic information, duration of AMD, smoking status and current use of dietary supplements. For patients using supplements, we also noted duration of use, reason for use, who recommended use, and type and dosage of supplements (including vitamin, mineral and herbal supplements). The exact dosages were confirmed by follow-up telephone interview. Cost estimates were determined by averaging retail prices from several local pharmacies. We compared methods of reaching the recommended dosages using various combinations of commercially available multivitamin formulations and individual beta-carotene, vitamin C and E, and zinc supplements. The goal was to match the dosage recommended in the AREDS (without exceeding it if possible) at maximum convenience and minimum cost and without increasing the risk of toxic effects.

Results: Of 108 patients with AMD surveyed, 85 (79%) were taking dietary supplements, and 73 (68%) were taking at least one AREDS ingredient. The mean dosages of beta-carotene, vitamins C and E, and zinc were all below those recommended in the AREDS. None of our patients met the recommended dosages for all four ingredients. We identified four methods of reaching recommended dosages using various combinations of ICAPS TR, Ocuvite and Vitalux as well as Centrum multivitamin and individual supplements.

Interpretation: Patients with AMD may not be receiving the dosages of beta-carotene, vitamins C and E, and zinc recommended in the AREDS. Until new formulations of high-dose antioxidant and zinc supplements are available in Canada, patients should be counselled to attempt to meet recommended dosages by using combinations of currently available supplements.