Men who take daily multivitamin supplements can reduce their risk of cataracts, according to a long-term study of nearly 15,000 male physicians.
As part of the Physicians’ Health Study II (PHS II), researchers based at Brigham and Women’s Hospital and Harvard Medical School in Boston conducted a randomized, double-blind trial from 1997 to 2011 of 14,641 US male doctors aged 50 years and older. Half of the men took a common daily multivitamin, as well as vitamin C, vitamin E, and beta-carotene supplements, and the other half took placebo pills.
In the placebo group, 945 cases of cataract developed, compared with only 872 cases of cataract in the multivitamin group, representing a 9% decrease in risk.
Even a modest reduction in risk of cataract has potential to improve public health outcomes. “If multivitamins really do reduce the risk of cataract, even by a modest 10%, this rather small reduction would nonetheless have a large public health impact,” said lead author William Christen, ScD, a researcher at Harvard Medical School.
The researchers also found a slight increase in age-related macular degeneration (AMD) risk among multivitamin users. There were 152 new cases of visually significant (best corrected visual acuity of 20/30 or worse) AMD in the multivitamin group compared with 129 in the placebo group, but the difference was not statistically significant.
This AMD finding seems to contradict results of other studies, such as the Age-Related Eye Disease Study (AREDS). But the researchers note that AREDS included daily zinc and a high-dose antioxidant combination of vitamin E, vitamin C, and beta-carotene. The multivitamin in PHS II included these nutrients and many others. All the nutrients were provided to the PHSII participants at the Recommended Dietary Allowance dose levels, which are much lower than the AREDS supplements. The objective of PHS II was to prevent new cases of AMD, and those with an AMD diagnosis at baseline were excluded; the objective in AREDS was to prevent AMD progression among those who already had the disease.
“This finding of more cases of AMD in the multivitamin group than in the placebo group, although not statistically significant, does raise some concerns,” said Dr Christen. “Clearly, this finding needs to be examined further in other trials of multivitamin supplements.”
The American Academy of Ophthalmology recommends the use of antioxidant vitamin and mineral supplements as recommended in the AREDS reports, including high daily doses of vitamin C, vitamin E, beta-carotene, zinc, and copper only for patients who have intermediate or advanced AMD. Current smokers and patients with a smoking history should be advised to avoid taking beta-carotene because of the increased risk of lung cancer and consider taking the other components of the AREDS formulation. The recent AREDS2 results would suggest that other nutrients, such as lutein and zeaxanthin, may be an appropriate substitution for beta-carotene in the formulation.
The ophthalmology academy does not have a recommendation for the use of nutritional supplements to prevent cataracts or delay their progression.
The researchers published their results in the February 2014, issue of Ophthalmology.