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Ophthalmologists continue to debate the best method of optimizing anti-oxidative processes in the eye. Some question the value of optimizing intake of these important nutrients through supplementation, and believe that dietary intake alone is adequate. In a recent EduFacts (volume 3, number 8) we reviewed a report from NHANES III, which showed that about a quarter of the population has a vitamin E plasma level of <20 µmol/L. It was also shown that vitamin supplementation was inversely associated with having a low plasma level of vitamin E. In the following EduFacts (volume 3, number 9) we reviewed a prospective study demonstrating that patients at or below this level were at increased risk of progression of early cortical cataract. An earlier case-control study (summarized in EduFacts volume 2, number 5) showed a decreased risk of cataract associated with vitamin supplement use. In this EduFacts we review some results, published in 1994, of the prospective Physicians Health Study, which suggested that use of multivitamin supplements is associated with decreased risk of cataract (1).

Methods:

The Physician's Health Study is a randomized double masked intervention trial, which evaluated the efficacy of low-dose aspirin therapy and beta-carotene for prevention of cardiovascular disease. The evaluation considered here was carried out as a sub-study. Study physician participants with no cataract at baseline (N=17,744) were followed an average of 5 years. At baseline, regular multiple vitamin supplement use was determined (never, past only, current) as well as single vitamin supplement use of vitamins C or E (never, past only, current). Vitamin A users were excluded because beta-carotene was an assigned treatment. Participants reported number of years of use. Other dietary covariables were collected. Follow-up was performed at 6-month intervals. Cataract diagnosis and/or extraction was determined by self-report among the physicians, verified, and detailed by the diagnosing ophthalmologists.

Results:

At baseline, 20% reported multivitamin use (12.5% multivitamin only; 7.5% multivitamin + vitamins C and/or E). During the average 5-year follow-up there were 370 incident cataracts and 109 cataract extractions with 10,983 person-years of observation. The main finding was that reported use of multivitamins was inversely associated with risk of incident cataract. The relative risk (RR), adjusted for possible confounding covariables, was 0.73 with a 95% CI of 0.0.54 to 0.99. This suggests a 27% decrease in risk. The RRs decreased with increasing durations of reported use (test for trend=0.06).

The authors considered these results as compatible with a hypothesis of decreased risk with supplement use, but pointed out the need for a long-term intervention trial.

References

1. Seddon JM, Christen WG, Manson JE, et al. The use of vitamin supplements and the risk of cataract among U.S. male physicians. Am J Public Health 1994;84:788-792.