A prospective study of vitamin supplement intake and cataract extraction among U.S. women.

We prospectively examined the association between vitamin supplement intake and the incidence of cataract extraction during 12 years of follow-up in a cohort of 47,152 female nurses. Women were 45 years or older and free of diagnosed cancer in 1980; others were added as they reached 45 years of age, for a total of 73,956 women. During 720,082 years of follow-up, 1,377 senile cataracts were diagnosed and extracted. Those who used multivitamins or separate supplements of vitamin C, E, or A did not have decreased risks of cataract as compared with nonusers even for use of 10 or more years. After adjusting for cataract risk factors, including cigarette smoking, body mass index, and diabetes mellitus, users of vitamin C supplements for 10 or more years had a relative risk (RR) of 0.95 [95% confidence interval (CI) = 0.76-1.20]. Associations were stronger among long-term vitamin C supplement users who were never-smokers (RR = 0.71; 95% CI = 0.47-1.08) and less than 60 years of age (RR = 0.72; 95% CI = 0.49-1.04). These findings suggest that there is little overall benefit of long-term use of vitamin supplements for risk of cataracts requiring extraction.