Vitamin E (alpha-tocopherol) is taken as a supplement by many people because of its anti-oxidant activity. It if often used to protect against heart disease. Vitamin E is found in normal healthy cell membranes and prevents formation of lipid peroxides.

Reports published over the last decade have generally documented decreased risk of opacities and/or cataract extraction associated with intake of various antioxidant vitamins or with computed "antioxidant intake scores". Study designs and specific conclusions were varied. This EduFacts will focus on two case-control studies, which support the protective role of vitamin E supplements against cataract formation formation.

In the case-control study by Robertson, Donner and Trevithick (1), 175 cataract patients were individually matched with 175 cataract-free controls. Cataract was defined as a lenticular opacity impairing vision. All cases had just undergone or were scheduled for cataract surgery. Controls were matched on age (within 5 years) and sex. All participants were interviewed in their homes. Detailed information on the use of nutritional supplements within the previous 5 years was obtained through interview. Paired multiple logistic regression analysis was used to determine relative risks while controlling for confounding variables. The major finding in the study was that there was a 44% decrease in risk of cataract (p=0.004) associated with reported use of vitamin E supplements compared with non-use during the prior 5 years.

Also in 1991, Leske, Chylack and co-authors reported the results of another case-control study of cataract risk factors (2). This study evaluated 1380 ophthalmology outpatients at 2 sites. They were aged 40-79 and were evaluated for opacity grade using a standardized system. Cases (N=945) were defined as having a nuclear, cortical or PSC opacity in at least one eye explaining a decrease in vision. Controls (N=435) had no lens opacities and were 20/20 or better in both eyes. Cases were similar to controls with respect to demographics, and possible confounders. Nutritional data were obtained using a questionnaire devised for a large government survey of nutrition and health that provided estimates of dietary intake of various vitamins over long periods. Use of supplements was ascertained by questionnaire. With respect to vitamin E, it was found that there was a 42% (p<0.05) decreased risk of mixed cataract associated with high dietary intake of vitamin E compared with low intake.

Use of multivitamins was also evaluated in this study. Reported intake of these supplements was associated with a 30-48% decrease in risk of cataract depending on the opacity type.

These studies, with similar design and methodology, both reported consistent levels of decreased risk of cataract associated with vitamin E intake through supplement use or relatively higher dietary intake.

References

1. Robertson JM, Donner AP, Trevithick JR. A possible role for vitamins C and E in cataract prevention. Am J Clin Nutr 1991;53:346S-351S.
2. Leske MC, Chylack LT Jr, Wu S. The lens opacities case-control study: risk factors for cataract. Arch Ophthalmol 1991;109:244-251.