Study finds daily multivitamin use may reduce cataract risk

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A randomized, double blind study of physicians who took part in the Physicians’ Health Study II found that those who received a daily multivitamin had a 9% lower risk of cataract - and a 14% lower risk of nuclear cataract- than those who received placebo. Given the prevalence of cataracts in the population at large, a 9% reduction in risk could have a significant public health impact.

Dr. Christen

By Ron Rajecki; Reviewed by William Christen, ScD

BOSTON-A vitamin a day keeps the cataracts away? Possibly. Long-term daily multivitamin use has been found to modestly decrease the risk of cataracts in a large cohort of male physicians aged 50 years or older.

Researchers at Brigham and Women's Hospital and Harvard Medical School conducted a randomized, double blind study from 1997 to 2011 of 14,641 male doctors age 50 and older who participated in the Physicians' Health Study II (PHS II). About one-half (7,317) were assigned to take a common daily multivitamin (Centrum Silver, Pfizer), while the other half (7,324 participants) took a placebo. The participants were also randomly assigned to vitamin C, vitamin E, and beta-carotene supplements.

The researchers followed the participants to identify how many participants in each group developed new cases of cataract and/or age-related macular degeneration (AMD). Endpoints were incident cataract or visually significant AMD responsible for a reduction in best-corrected visual acuity to 20/30 or worse.

Examining the study

During an average of 11.2 years of treatment and follow-up, a total of 1,817 cases of cataract and 281 cases of visually significant AMD were confirmed. There were 872 cataracts among the 5,736 physicians who were included in the final analysis of the multivitamin group, and 945 cataracts among the 5,761 physicians who were included in the final analysis of the placebo group (p = 0.04).

The findings represent a 9% decrease in overall cataract risk in the multivitamin group. In addition, the multivitamin group had a 13% lower incidence of nuclear cataract.

The reduction in risk for cataracts in the multivitamin group did not extend to AMD. For visually significant AMD, there were 152 cases among the 7,111 physicians who were included in the final analysis of the multivitamin group, and 129 cases among the 7,122 physicians in the placebo group (p = 0.15).

The study was published in Ophthalmology.

The study’s lead author, William G. Christen, ScD, said the findings in this large-scale randomized trial are consistent with the results of previous trials of multivitamin use in cataract prevention.^1,2 He added that given an estimated 10 million adults in the United States have impaired vision caused by cataract, even the relatively modest 9% decrease in risk has the potential to significantly improve public health outcomes.

“Our finding regarding the reduced risk of cataract among those taking a daily multivitamin reinforces the findings of two other large clinical trials,” said Dr. Christen, associate professor of medicine, Harvard Medical School, and associate epidemiologist, Brigham and Women's Hospital. “For AMD, we found no significant increase or decrease on the primary end point of visually significant AMD, but we did see more cases of AMD overall in the multivitamin group than in the placebo. Although the difference was not statistically significant, the finding does raise some concerns that we think need to be investigated further in other trials.”

Diving deeper

Dr. Christen added that there were a few limitations in this study-Centrum Silver was selected as the multivitamin at the inception of the PHS II study in 1997, and the same formulation was used throughout the trial. However, the formulation has since been changed and several nutrients have been added, including lutein, although these nutrients couldn’t be tested in PHS II.

“The observational data suggest that there may be an added benefit - perhaps with both eye endpoints - from the addition of lutein, but we couldn’t investigate it,” Dr. Christen said. “Findings from the Age-Related Eye Disease Study 2 suggest a benefit of lutein in certain subgroups of patients, so I think it’s important to find out exactly what the impact of adding lutein to the Centrum formulation is.”

In addition, he said the results of this study of well-nourished, male physicians may not extend to women or less-nourished patient populations.

Ultimately, while the results for cataract are encouraging, Dr. Christen cautioned against perceiving daily multivitamins as a “magic bullet” to prevent age-related eye problems.

“I think the best advice continues to be a diet high in fruits and vegetables,” he said. “However, there hasn't been a lot of good news for multivitamins recently, and although it’s a small statistical difference on cataract, it certainly can be interpreted as good news.”

References

1. Sperduto RD, Hu TS, Milton RC, et al. The Linxian cataract studies. Two nutrition intervention trials. Arch Ophthalmol 1993;111:1246–53.

2. Clinical Trial of Nutritional Supplements and Age-Related Cataract Study Group. A randomized, double-masked, placebo-controlled clinical trial of multivitamin supplementation for age-related lens opacities: Clinical Trial of Nutritional Supplements and Age-Related Cataract report no. 3. Ophthalmology 2008;115:599–607.

William Christen, ScD
Phone: 617-732-5500
E-mail: wchristen@partners.org
Dr. Christen received research funding support from the National Institutes of Health and DSM Nutritional Products Inc. (formerly Roche Vitamins)

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