Long-Term Vitamin C Use Decreases Cataracts

A study tracking the effects of long-term vitamin C supplementation finds that women who took the antioxidant vitamin for at least 10 years significantly lowered their risk of developing cataracts.

Oxidative stress, particularly ultraviolet light exposure, seems to play a central role in cataract development. Higher intakes of antioxidant vitamins C and E and carotenoids, however, can lower this common cataract risk, according to previous laboratory and population studies.

The latest effort to examine the relationship between long-term vitamin C intake and cataracts began in 1976. Paul Jacques and colleagues at the USDA Human Nutrition Research Center on Aging at Tufts University, Boston, selected 247 women ages 56 to 71 who had never been diagnosed with cataracts from a pool of 121,700 female nurses. The researchers purposely over-sampled women with high and low vitamin C intakes to add statistical power to their observations.

Researchers ranked women according to vitamin C intake based on questionnaires taken in 1980, 1984 and 1986. Women in the lowest quintile consumed less than 93 mg of vitamin C/day. Women in the highest quintile, 92 percent of whom took either a vitamin C supplement or a multivitamin, consumed more than 359 mg/day. The RDA for vitamin C is 60 mg/day.

Between 1990 and 1992, women with the highest and lowest vitamin C intakes received a detailed eye exam. After adjusting for risk factors such as diabetes, cigarette smoking and sun exposure, researchers found that women who used vitamin C supplements for more than 10 years had a 75 percent lower prevalence of early lens opacification (cataract formation) and an 83 percent reduction of moderate lens opacification. Adjusting for the intake of other antioxidant nutrients did not alter this relationship. Women who used vitamin C supplements for less than 10 years also had a lower prevalence of cataracts, but the trend was not statistically significant.

The authors concluded that long-term vitamin C supplementation may substantially reduce the development of age-related lens opacities and called for further studies designed to measure intake or to intervene with supplements for at least 10 years.

In the meantime, people can lower their cataract risk by wearing sunglasses outside during the day, quitting smoking, and eating citrus fruits, peppers and dark green leafy vegetables.

--Amer J Clin Nutr, 66: October 1997

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