Vitamin E Fails to Slow AMD

Source: Tufts University
August 8, 2002 (Reviewed: August 20, 2004)

Age related macular degeneration (AMD) is the leading cause of vision loss in developed countries, yet scientists have still to decipher its causes or develop a cure. They've been hopeful that antioxidant nutrients might be able to prevent the oxidative damage to the retinal pigment epithelium that appears to set the disease in motion. But this prevention strategy did not prove to be effective in one recent study --- published in British Medical Journal --- on the effects of vitamin E supplements on risk of AMD.

Supplements no help

Australian researchers recruited 1,193 healthy adults aged 55-80 and randomly assigned them to receive either 500 IU vitamin E or placebo daily for 4 years. Retinal photographs --- repeated yearly and graded according to set international standards --- were used to assess change over time. Outcomes of interest were development of early AMD, progression of existing AMD, or changes in visual acuity and visual function.

Four years of vitamin E supplementation apparently had no effect on the development of AMD in this population. There was no statistical difference between the two groups in incidence of early AMD or in progression of existing disease.

Study limitations

These findings add to those of earlier studies on the effect of vitamin E on AMD that have produced inconclusive and sometimes contradictory results. One of the more promising outcomes --- from the Age-Related Eye Disease Study --- showed that an antioxidant combination of vitamin C, vitamin E, beta-carotene, and zinc slowed disease progression in those with moderately advanced AMD in both eyes. This study, though, did not look at the effect of vitamin E independent of the other nutrients.

The authors of both the study and the accompanying editorial point out that 4 years may not be enough time to adequately assess the effect of antioxidants on the progression of AMD. Longitudinal studies that have documented a link between dietary antioxidants and reduced disease risk have generally captured the effects of long-time dietary habits, rather than shorter-term interventions. It's possible, say the authors, that the health benefits of vitamin E supplements come from years of use or in combination with other nutrients.

The authors of the editorial also suggest that the sample size of this study may have been too small to wield adequate predictive power. Or, in fact, vitamin E may not have a role to play in the prevention of AMD.

Advice to patients

There's not yet a clear nutrition message on how to eat to preserve eye health. Antioxidants may help, but how much, in what form, and for how long remain to be determined. Given what we already know about antioxidants and eye health, though, it seems prudent to aim for a diet that includes at least 5 daily servings of fruits and vegetables (to include several high in vitamin C) and several servings of vitamin E-rich foods, including vegetable oils, wheat germ, peanut butter, nuts, and seeds. Although not included in this particular study, foods high in lutein --- notably dark green leafy vegetables --- may also provide some protection against AMD.

Not smoking and keeping serum cholesterol levels in check --- both of which help keep blood vessels healthy --- may reduce the risk. It's also possible that wearing sunglasses in direct sunlight might help control the oxidative damage that leads to AMD.

Source

• Vitamin E supplementation and macular degeneration: randomised controlled trial. H. Taylor, G. Tikellis, L. Robman,  et al., BMJ, 2002, vol. 325, pp. 1--6

Related Links
Antioxidants and Eye Health
Cataracts and Nutrition
Risk Factors for Age-Related Macular Degeneration (AMD), Including Dietary Fat and Fish
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