The decades-old advice, "eat carrots to see in the dark" may need to be modified to "eat beta carotene," a form of vitamin A that is abundant in carrots and other deep-colored fruits and vegetables. Harvard University researchers examined whether taking beta carotene supplements protects against age-related cataracts, a clouding of the eye that interferes with vision. Their findings are published in Archives of Ophthalmology.

Assessing the effect of supplements

The 22,071 volunteers were healthy, cataract-free, male physicians, who were part of a large, ongoing health study that began in 1983. After collecting medical and lifestyle information such as smoking and drinking habits, weight, and use of multivitamins, half of the volunteers were assigned to take a beta carotene supplement (50 milligrams every other day), while the rest were given a sugar pill. Every year the volunteers reported any changes in health status, including whether they had been diagnosed with cataracts, or had undergone surgery to correct cataracts.

Beta carotene benefits

After 12 years, about 2,000 cataracts and almost 1,200 cataract surgeries were reported and confirmed by the volunteers' eye doctors. In most cases, beta carotene did not appear to lower the risk of getting cataracts. However, one group of volunteers who appeared to benefit from the beta carotene was smokers. Current smokers who were taking the beta carotene supplement reduced their cataract risk by about 25% compared with smokers taking the sugar pill.

Smoking is clearly harmful

Smoking itself increases cataract risk, and stopping smoking is more protective for your eyes and overall health than taking a vitamin supplement. In fact, among those taking the sugar pill, smokers had a 65% greater risk of developing cataracts than those who did not smoke. Even those smokers taking a supplement had more cataracts than nonsmokers who were not taking the supplement.

What you can do

Beta carotene is one of several antioxidants - substances found in fruits and vegetables - that may help keep eyes healthy, but it is not yet clear exactly how much is needed to have a measurable effect. It is also not yet evident that dietary supplements are an adequate substitute for the real thing, especially since deeply-colored fruits and vegetables like broccoli, spinach, sweet potatoes, apricots, and red peppers offer many other nutrients in addition to beta carotene.

More than half of Americans over age 65 have a cataract. In the early stages, vision may be improved by using stronger light for reading and other close work or wearing corrective glasses, but over time surgery is often necessary. For healthy eyes, quit (or never start) smoking, wear sunglasses, and if you are over age 60, visit your eye doctor every two years.