High Supplement Use of Iron and Calcium Linked to Higher Incidence of Glaucoma

According to findings first reported at the American Academy of Ophthalmology 2012 Annual Meeting, researchers from the University of California, San Francisco found that people who take higher doses of iron and calcium through supplements have a higher rate of developing glaucoma. However, the researchers found that those whose dietary intake of calcium and iron was high have decreased odds of developing glaucoma.

It is believed the difference is because supplements and vitamins taken through diet are either absorbed differently or “act in biologically different ways.”

Research Survey

Researchers surveyed the diets of 6316 National Health and Nutrition Examination Survey (NHANES) participants between 2005 and 2008 who were 40 years or older. Estimated usual intake of calcium and iron were put into quintiles, and age, race, sex, and comorbities were placed into a model to produce a ratio for those who self-reported glaucoma.

Of the 6316 participants, 422 developed glaucoma. Examination of these 422 participants showed total higher intakes of calcium and iron as supplements. However, when dietary intake of nutrients in food was examined, researchers found the odds ratios diminished as the intake of the vitamins lessened.

The lead researcher explained that, “we can hypothesize that high total intakes of calcium or iron, driven by supplement use, may serve as potential environmental stressors.” She goes on to say, “And this, combined with a background of already impaired calcium or iron homeostasis due to aging or other factors, may lead to damage of the trabecular meshwork or ganglion cell death, thus ultimately increasing the risk of glaucoma.”

She emphasized that this is a hypothesis that needs much further research before a recommendation can be made.

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