PURPOSE. To investigate the relationship between supplementary consumption of the oxidants calcium and iron and caffeine and the prevalence of glaucoma. METHODS. This cross-sectional study included 3833 participants 40 years of age, who reported a presence or absence of glaucoma. Participants were interviewed regarding the use of dietary supplements and antacids during the preceding 30-day period. Data pertaining to the supplementary intake of calcium, iron and caffeine was aggregated and

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... d into quintiles. Information regarding the presence or absence of glaucoma and demographics, comorbidities, and health-related behavior was obtained via interview. RESULTS. Participants who consumed 800 mg/d of supplementary calcium or 18 mg/d of supplementary iron had significantly higher odds of having been diagnosed with glaucoma than did those who had not consumed supplementary calcium or iron, after adjustment for potential confounders. Concurrent consumption of both calcium and iron above these levels was associated with still greater odds of having been diagnosed with glaucoma. Compared with participants whose cumulatively updated total caffeine consumption was <125 mg/day, participants who consumed ≥500 mg/day had a trend toward increased risk of glaucoma. CONCLUSIONS. These results suggest that there may be a threshold intake of iron, calcium and caffeine above which there is an increased risk of development of glaucoma. Prospective longitudinal studies are needed, to assess whether oxidant intake is a risk factor for development and progression of glaucoma.