Effect of selenium and vitamin E supplements on the development and progression of cataracts
Reviewed by Lona Jawaheer

The Selenium and Vitamin E Cancer Prevention Trial (SELECT) investigated the influence of dietary supplements on the development of prostate cancer in a group of 35,533 middle aged and older, apparently healthy men. The SELECT Eye Endpoint (SEE) study is an ancillary study involving a subset of 11,267 of the SELECT participants that looked specifically into the impact of selenium (200μg per day from L-selenomethionine) and vitamin E supplements (400IU per day of all rac-α-tocopheryl acetate) on the development of cataract in those patients. Participants with a pre-existing diagnosis of cataract were excluded from analysis in the SEE study. Group participants were randomised into one of four treatment arms: selenium only, vitamin E only, combination of selenium and vitamin E, placebo. The participants were followed up at six monthly intervals and were asked to report new diagnoses of cataract or cataract extraction. Over a mean period of 5.2 years (SD 1.6 years), 185 patients developed cataracts in the selenium group compared to 204 in the no-selenium group (HR, 0.91; 95% CI, 0.75-1.11; p=.37), and 99 patients underwent cataract extraction in the selenium group compared to 120 in the no-selenium group (HR, 0.84; 95% CI, 0.64-1.09; p=.19). In the vitamin E group, 197 patients developed cataracts in the treatment group compared to 112 in the placebo group (HR, 1.02; 95% CI, 0.84-1.25; p=.81), and 114 patients underwent cataract extraction in the treatment group compared to 105 in the placebo group (HR, 1.08; 95% CI, 0.83-1.41; p=.58). The trial was terminated prematurely because of possible adverse effects of the supplements, including a 17% increase in the rate of prostate cancer in the vitamin E group. This is the first randomised control trial (RCT) that has looked at the impact of selenium in isolation on the development of cataract, and it does not provide evidence of any large beneficial effect (although a smaller but potentially important beneficial effect cannot not be ruled out). The lack of impact of vitamin E on cataract development seen in this trial echoes the findings of previous randomised trials.

Age-related cataract in men in the Selenium and Vitamin E Cancer Prevention Trial Eye Endpoints Study. A randomized clinical trial.
Christen WG, Glynn RJ, Gazing, M et al.
JAMA OPHTHALMOLOGY
2015;133(1):17-24.