Iron and calcium supplementation above a certain level may increase your risk of developing glaucoma, says recent research.
In a cross-sectional study of participants in the 2007-2008 National Health and Nutrition Examination Survey, 3,833 people aged 40 or older were interviewed about their use of dietary supplements and antacids (which usually contain calcium) during the previous 30 days.
Those who took at least 800 mg per day of supplementary calcium or at least 18 mg per day of supplementary iron (both are oxidants) had a greater chance of glaucomatous disease than those not taking these supplements. In fact, taking both iron and calcium above these levels increased the odds of developing glaucoma even more.
For perspective, here are the amounts of iron and calcium found in some popular supplements:
The researchers noted that further study is needed to decide whether oxidant intake is a definite risk factor for the eye disease.