Glaucoma Prevalence and the Intake of Iron and Calcium in a Population-based Study

Purpose: Previous work has suggested a possible relationship between nutritional supplementation with iron and calcium, and a diagnosis of glaucoma. The present study investigates the association between dietary and total calcium and iron consumption with a diagnosis of glaucoma. Methods: This cross-sectional study included 6316 participants in the National Health and Nutrition Examination Survey (NHANES 2005-2008), age 40 or older, who participated in the dietary interview portion of NHANES. Intake of the oxidants calcium and iron was assessed using the National Cancer Institute Method of analyzing data from multiple 24-h dietary recall interviews. Participants self-reported the presence or absence of glaucoma as well as information pertaining to demographics, health-related behaviors and comorbidities. Results: Adjusted odds of glaucoma increased with higher total consumption of calcium (p-trend <0.0001) and iron (p-trend <0.0001). Adjusted odds of glaucoma was significantly greater for total calcium intake at the third (OR 1.58, 95% CI 1.32-1.89) and fourth quintile levels (OR 1.21, 95% CI 1.03-1.43) and for total iron intake at the fourth (OR 2.95, 95% CI 2.52-3.45) and fifth quintile levels (OR 1.58, 95% CI 1.36-1.83), compared with the corresponding lowest quintile of intake. In contrast, a tendency towards decreased odds of glaucoma was observed with increasing dietary calcium (p-trend = 0.0008) and iron intake (p-trend = 0.0022). Conclusions: While greater total consumption of calcium and iron may be associated with increased odds of glaucoma, dietary rather than supplemental consumption of these oxidants was found to be associated with lower odds of glaucoma. Additional research is necessary to elucidate the relationship between glaucoma and oxidant intake from foods versus supplements, and to prospectively evaluate whether oxidant intake is related to glaucoma incidence and progression.