According to the results of a large randomised, placebo-controlled trial, the use of vitamin E or C supplements does not appear to alter the risk of developing cataracts.
The authors note that oxidative damage is a prominent feature of cataracts, therefore nutritional research has focused on the link between dietary intake of nutrients with antioxidant properties and the risk of cataract. Observational data have generally supported the antioxidant hypothesis; however the results from prospective trials of vitamin C and E supplements have been disappointing.
In this paper, they report the final results for cataracts from the vitamin E and vitamin C components of the Physicians' Health Study (PHS) II. The PHS II is a randomized, double-masked, placebo-controlled trial designed to examine the effects of vitamin E, vitamin C, and a multivitamin in the prevention of cancer and cardiovascular disease in a large population of male physicians.
PHS II randomised 11,545 apparently healthy US male physicians aged ≥50 years without a diagnosis of cataract at baseline to receive 400IU of vitamin E or placebo on alternate days, 500mg of vitamin C or placebo daily. The main outcome was incident cataract responsible for a reduction in best-corrected visual acuity to 20/30 or worse, based on self-report confirmed by medical record review.
Over an eight-year follow-up period, there were 1,174 cataracts in the total cohort. There was no difference in the rate of cataract formation in the active vitamin E group (579/5771) and in the vitamin E placebo group (595/5774) (hazard ratio 0.99; 95% CI 0.88-1.11). Similarly there was no difference between the active vitamin C group and the placebo group (593/5779 versus 581/5746; HR 1.02; 95% CI 0.91-1.14).
The authors conclude that their findings from a population of middle-aged and older, generally well-nourished men indicate that long-term supplementation with high-dose vitamin E and vitamin C, either alone or in combination, has little effect on rates of cataract diagnosis and extraction.