Null Findings for Supplements to Prevent Cataracts

March 14, 2015
Jeannette Y. Wick, RPh, MBA, FASCP

Some researchers have proposed that vitamin E and selenium supplements may inhibit cataract formation.

The human eye concentrates vitamin E in lens fibers and membranes, and it also contains high levels of the trace mineral, selenium. For these reasons, some researchers have proposed that supplements of both may inhibit cataract formation.

Although observational studies have suggested that patients with higher dietary intake of vitamin E and selenium may be less likely to develop cataracts, researchers from Brigham and Women's Hospital and Harvard Medical School recently published the results of a large study that indicated supplementation may not help.

The Southwest Oncology Group originally designed and conducted the randomized, placebo-controlled Selenium and Vitamin E Cancer Prevention Trial (SELECT) involving 35,533 men, but it was terminated early when they found that selenium and vitamin E—taken alone or together for an average of 5.5 years—did not prevent prostate cancer.

The Eye Endpoints Study was an ancillary study of the trial that examined data from 11,267 participants monitored at 128 SELECT sites. Patients received various combinations of selenium 200 mcg daily and vitamin E 400 IU daily. Adherence to supplementation remained high during follow-up, averaging 83% at year 1 and 65% at year 5, which are good rates for a long-term study.

Patients took the study drugs for slightly more than 5.5 years. The researchers identified 185 cases of cataract in the selenium-treated group and 204 in the no-selenium group. They also discovered 197 cataract cases in the vitamin E-treated group and 192 in the placebo group.

Those assigned to selenium (±vitamin E) or selenium (with or without vitamin E) had a non-significant 9% reduction in diagnosed cataract. Therefore, long-term daily selenium and/or vitamin E supplementation was not associated with a decreased likelihood of cataracts in the study.

These null findings in cataract prevention are consistent with the overall negative results related to vitamin E in previous randomized trials. For instance, the Women’s Health Study and Physicians’ Health Study II also found no benefit of vitamin E in cataracts, even with longer treatment durations.