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Choosing between strong bones and healthy eyesight is not a choice anyone should have to make. But conflicting studies concerning calcium supplements and age-related macular degeneration (AMD) has created anxiety for many older Americans.
While a previous study pointed to a possible connection between higher calcium intake and AMD, a more recent report showed the opposite.
So what is the current state of calcium intake and AMD, and should seniors be prioritizing their bone health over the well-being of their eyesight?
Before tackling that question, a quick review of what calcium and AMD are and what effect they can have.
Calcium
Calcium is crucial for building and maintaining bone strength. Not having enough calcium in your diet can result in lower bone mass, which for older adults can be a risk factor for osteoporosis.
The body doesn’t produce calcium on its own and must be gathered through a diet that has calcium-rich foods including dairy (milk, yogurt, cheese); dark leafy green vegetables (kale and broccoli); and certain fish (sardines, salmon).
Taking calcium supplements is common for people who have dietary restrictions, or who simply don’t get enough calcium from their diet.
Age-related macular degeneration (AMD)
AMD is an eye disorder that results in damaged central vision, and is the leading cause of severe vision loss in adults over the age of 50. The Center for Disease Control and Prevention estimates that 1.8 million Americans age 40 years and older are affected by AMD, and that number is estimated to reach 2.95 million in 2020.
The CDC also claims that AMD is the leading cause of permanent impairment of reading and fine or close-up vision among people aged 65 years and older.
AMD affects the macula, the central part of the retina that allows the eye to see fine details, and has two forms, wet and dry. Dry AMD is when the macula thins over time and is the more common type of AMD, accounting for 70% to 90% of cases according to the CDC. The wet variety occurs when abnormal blood vessels leak fluids into the macula.
Conflicting studies
Confusion about calcium intake and AMD stems from contrasting studies over the past five years.
A 2015 study published in JAMA Ophthalmology linked self-reported calcium supplementation with increased prevalence of AMD. The study examined the results from the 2007-2008 National Health and Nutrition Examination Survey (NHANES), which consisted of 3191 participants over the age of 40 responding to questions about dietary supplement and antacid use.
Participants who reported taking more than 800 mg/d of supplementary calcium were found to have higher odds of an AMD diagnosis; the association is stronger in older individuals.
However these results were contradicted in March of 2019 by another report published in JAMA Ophthalmology, which found dietary and supplementary calcium intake to be associated with lower incidence of AMD progression.
This study analyzed findings from the Age-Related Eye Disease Study (AREDS), which was conducted between 1992-2001 and lists as one of its goals to “assess the clinical course, prognosis, and risk factors of AMD and cataract.”
There was also the Blue Mountain Eye Study, released in 2014, which linked lower levels of dairy consumption with higher prevalence of AMD.
So what gives?
Speaking exclusively with Dr. Emily Chew, clinical spokesperson for the American Academy of Ophthalmology, and the deputy clinical director at the National Eye Institute (NEI), we were able to get some clarity on the matter.
Dr. Chew’s stance was clear: “Taking calcium is not harmful for you.”
Dr. Chew explained how the conflicting results of the studies mentioned above can be attributed to the different methodologies in research. The 2015 study was a cross-sectional study, meaning it provided data from a certain pool of participants at a specific moment in time.
The 2019 study, in contrast, was a longitudinal study which observed the same subjects repeatedly over a 10-year period.
Longitudinal studies are greater in scope and more effective at establishing cause-and-effect relationships, while any connections resulting from cross-sectional studies are harder to verify since there is no information previous to, or following the study period.
Thus the 2015 study only represents a snapshot of one particular moment, and any relationship between supplementary calcium intake and AMD could be the random linking of factors.
The verdict
When asked if this was currently a debate at all, Dr. Chew thinks not, responding that she’s “not aware of any major camps that are debating this” and that as far as she knows “nobody recommends not taking calcium” out of concern for AMD.
As far as eye health Dr. Chew offered this: “All the things you can do to live a healthy lifestyle will also be good for your eyes as well.” So eat well, get exercise, and take your calcium supplements as needed.
Because it appears you don’t have to choose between strong bones or strong eyes.
