Long-term use of high-dose vitamins E and C, alone or combined, has no effect in preventing the development of cataracts in men, according to the latest findings of the Physicians’ Health Study II reported in the November issue of Archives of Ophthalmology.
The PHS II, a randomized, double-masked, placebo-controlled trial, studied the effectiveness of vitamins E and C and a multivitamin in preventing cancer and cardiovascular disease among 14,641 apparently healthy U.S. male physicians aged 50 years or older. Incident cataract was a secondary end point.
Prospective observational studies have suggested that intake of vitamins E and C helps prevent the oxidative damage to the lens that leads to cataract. However, completed randomized trials have shown little beneficial effect of either vitamin, whether used alone or in combination with other supplements – even with as many as 10 years of treatment.
For this study, Dr. William G. Christen from Brigham and Women’s Hospital and Harvard Medical School, Boston, and his colleagues randomized 11,545 subjects as follows: 5,771 to receive 400 IU of vitamin E every other day, 5,774 to receive a vitamin E placebo every other day, 5,779 to receive 500 mg of vitamin C daily, and 5,746 to receive a vitamin C placebo daily (Arch. Ophthalmol. 2010;128:1397-1405). The researchers distributed baseline characteristics, including risk factors, evenly among the groups.
During a mean follow-up of 8 years, there were 579 cataracts in the vitamin E group, 595 in the vitamin E placebo group, 593 in the vitamin C group, and 581 in the vitamin C placebo group. There appeared little difference among patients with known or possible risk factors. There were 801 cataract extractions during this period.
Supplementation with vitamins E and C had no significant effect on diagnosed cataract or extraction, or on cataract subtype (nuclear, cortical, or posterior subcapsular). In the vitamin C group, there was a possible, but statistically nonsignificant, trend toward increased risk in those with a reported history of cardiovascular disease.
When interpreting these results, the researchers caution that several factors must be considered. For example, participants were generally well nourished, so findings might not apply to less well nourished populations. Also, the doses of both vitamins used were higher than normal dietary levels and levels used in observational studies, so even higher doses would probably yield no benefits. Although follow-up lasted 8 years, cataracts develop slowly over many years and may require longer periods of treatment, and possibly treatment at younger ages.
Finally, the PHS II excluded participants with known cataract. Many previous trials included patients with lens opacities at baseline, so intervention in those trials may have occurred too late in the disease process to have a material effect on rates of cataract, the researchers said.
The authors reported no financial disclosures. Support for the study came from grants funded by the National Eye Institute, the National Institute on Aging, the National Institutes of Health, and BASF Corp. The study was sponsored by BASF, Wyeth Pharmaceuticals, and DSM Nutritional Products, which had no role in the design and conduct of the study; in the collection, analysis, and interpretation of the data; or in the preparation, review, and approval of the manuscript.