News

Can antioxidant vitamins prevent age-related macular degeneration?

October 6, 2013

A new review suggests that there is not enough evidence that taking supplements with vitamins C and E, or carotenoids, such as beta-carotene, lutein, and zeaxanthin, prevents or delays the onset of age-related macular degeneration. Experts criticize the review as flawed.

To examine if taking antioxidant vitamin or mineral supplements can prevent the development of age-related macular degeneration (AMD), the review analyzed the results of four randomized controlled trials (RCTs) involving a total of 62,520 healthy people (1). The data analysis showed that taking vitamin E and beta-carotene supplements was unlikely to prevent the onset of AMD. In addition, the researchers stated that there was not enough evidence from RCTs that other antioxidant supplements and commonly marketed combinations with vitamin C, lutein and zeaxanthin, selenium, and zinc decrease AMD risk.

Experts criticized the review, arguing that it was another example of the kind of flawed analysis that disregards important and valid trials, and compares studies that are not really comparable. The current review did not include the AREDS study (2), a well-designed randomized controlled trial involving a large number of AMD patients, which showed that taking a formulation of antioxidants (beta-carotene, vitamin C and E, and zinc) can significantly reduce the risk of advanced AMD and its associated vision loss. The authors justified the exclusion, stating that the participants were not free of AMD at the beginning of the study. On the other hand, the authors included the ATBC study (3), although it was totally unknown if its participants were free of AMD at the start of the trial. In addition, the studies analyzed whose participants represented the majority of the evaluated individuals (ATBC, PHS I and WHS) originally did not have AMD prevention as their primary objective. It would by no means be valid to conclude from this review that lutein and zeaxan-thin have no effects on AMD risk the experts noted. While the current review only looked at AMD prevention, an earlier systematic review and meta-analysis concluded that people with AMD, or the early signs of the disease, may experience some benefit from taking supplements as used in the AREDS trial (4).

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 trace elements (selenium and zinc) may be less likely to get AMD. In addition, observational and experimental data suggest that antioxidant supplements may delay the progression of AMD and vision loss.

References

  1. Evans J. R. and Lawrenson J. G. Antioxidant vitamin and mineral supplements for preventing age-related macular degeneration. The Cochrane Collaboration. Published online June 2012.
  2.  The 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. Arch Ophthalmol. 2001; 119(10).
  3.  The Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group. The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. N Engl J Med. 1994; 330(15):1029–1035.
  4. Evans J. Antioxidant supplements to prevent or slow down the progression of AMD: a systematic review and meta-analysis. Eye (Lond). 2008; 22(6):751–760.