New findings from a USDA study of 247 women confirm that long-term use of vitamin C supplements substantially reduces the risk of cataract--a clouding of the eye's lens. There were 77 percent fewer early-stage cataracts among the women who took the supplements daily for more than 10 years than among those who didn't supplement.

Cataracts are thought to result from oxidation of lens proteins, and vitamin C prevents oxidation, the researchers said. But women who took the supplements for less than a decade had no detectable difference in cataract prevalence, according to findings published in the October issue of the American Journal of Clinical Nutrition.

The study was conducted by Paul F. Jacques, Allen Taylor and other researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, Boston, and colleagues with the Harvard University Nurses Health Study. The Boston center is funded by USDA's Agricultural Research Service.

The findings emphasize that cataracts are a chronic condition that takes many years to develop and therefore requires a long-term solution, the researchers concluded. They selected the participants from the 21-year-old Nurses Health Study based on high and low vitamin C intakes.

The findings corroborate a 1992 report that linked 10-plus years of vitamin C supplements with far fewer cataract surgeries among nurses in the larger Harvard study.

In the current study, the supplement users took at least 500 milligrams of vitamin C daily in addition to food and multivitamin sources. Unfortunately, there were too few women in this study to assess whether long-term vitamin C intake from foods or multivitamins protects against cataracts. None of the women had been previously diagnosed with the condition, and each had reported her food and supplement intake several times before being examined for lens clouding.

Scientific contacts: Paul F. Jacques or Allen Taylor, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, Mass. Jacques: phone (617) 556- 3237, paul@hnrc.tufts.edu. Taylor: phone (617) 556-3155, taylor_c1@hnrc.tufts.edu. Fax (617) 556-3344.