Calcium supplementation may increase macular degeneration

Calcium supplementation has previously been associated with cardiovascular risk (search 'calcium' for earlier posts), most likely by opposing the anti-inflammatory activity of magnesium. A study just published in JAMA Ophthalmology offers evidence that calcium supplementation may similarly promote age-related macular degeneration (AMD).

"Despite widespread use of calcium supplementation among elderly people, little is known about the association between such consumption and the prevalence of age-related macular degeneration (AMD) in the United States."

Calcium supplementation increased odds for AMD

The authors investigated the link between calcium supplementation and the prevalence of AMD in a sample of 3191 participants 40 years and older who were evaluated for the presence or absence of AMD by fundus photography. The level of calcium supplementation was divided into quintiles and correlated with fundus photographs graded for the presence or absence of AMD. The odds were then calculated  for an AMD diagnosis among participants in each quintile of self-reported calcium vs participants not on calcium supplementation after adjusting for confounders. More than 800 mg per day worsened the odds:

"A total of 248 participants (7.8%) were diagnosed with AMD. Mean ages were 67.2 years for those with AMD and 55.8 for those without AMD. After adjustment for potential confounding variables, study participants who self-reported consumption of more than 800 mg/d of supplementary calcium were found to have higher odds of an AMD diagnosis based on fundus photography evaluation compared with those not self-reporting supplementary calcium consumption. The association between self-reported supplementary calcium intake and AMD was stronger in older than younger individuals. A clear dose-response association between the quintiles of self-reported supplementary calcium intake and AMD was not established."

Those who took more than 800 mg per day of supplementary calcium were almost twice as likely to develop age-related macular degeneration.

Risk:Benefit of calcium supplementation should be weighed carefully

This study shows association, not causation. But bearing in mind that osteoporosis is not a calcium deficiency disorder (in osteoporosis the protein matrix to which calcium binds is deficient) and that opposing the anti-inflammatory activity of magnesium may have an array of unwelcome consequences, clinicians should carefully consider whether calcium supplementation is indicated on an individual basis. The authors conclude:

"Self-reported supplementary calcium consumption is associated with increased prevalence of AMD, with the findings suggesting a threshold rather than a dose-response relationship. The stronger association in older individuals may be due to relatively longer duration of calcium supplementation in older individuals."