Higher Calcium Intake Tied to Slower AMD Progression

By David Douglas

March 29, 2019

NEW YORK (Reuters Health) - Higher levels of dietary and supplementary calcium intake are associated with a lower risk of progression to late age-related macular degeneration (AMD), according to a secondary analysis of data from a large trial.

Earlier research on the possible association has had mixed results, note Dr. Emily Y. Chew and colleagues at the National Institutes of Health, in Bethesda, Maryland, in JAMA Ophthalmology, online March 21.

"Our retrospective study found no evidence that calcium increases the risk of AMD, which is important because an earlier study had suggested that higher calcium intake increases the risk," she told Reuters Health by email. "Calcium may even protect against AMD, but we need more research on this point. People who need to take calcium for another medical reason, such as osteoporosis, should know that they are not increasing their risk of AMD by taking the mineral."

The researchers analyzed data from the AREDS trial conducted between 1992 and 2001, which involved more than 4,700 participants with AMD of various degrees of severity.

Using baseline self-reported dietary or supplementary calcium intake, the team found that the 778 participants in the highest quintile of dietary calcium intake had a significantly lower risk of developing late AMD than the 839 in the lowest quintile (hazard ratio, 0.73).

This was also true of central geographic atrophy (HR, 0.64); there was a drop in any geographic atrophy (HR, 0.80; P=0.05). The participants in the highest tertile of supplementary calcium intake also had a significantly lower risk of developing neovascular AMD (HR, 0.70).

When stratified by sex, there were similar findings in women for both types of calcium intake and in men for dietary calcium intake, but too few men (81) took calcium supplements to allow for analyses.

Dr. Chew stressed, "our study was not able to control for confounding factors with respect to calcium intake. So for example, people who make a point of getting recommended calcium, may also be likely to exercise, eat omega-3-rich foods such as fish, and avoid smoking. Those types of healthy lifestyle choices lower the risk of AMD progressing to a late stage. So on the basis of this study, it's not possible to determine if the AMD benefit was due to the high calcium intake or the healthy lifestyle."

Dr. Carol Yim Lui Cheung of The Chinese University of Hong Kong, co-author of an accompanying editorial, told Reuters Health by email, "This study provides evidence to suggest that a higher nutritional intake of calcium is not harmful to the macula and may even have some additional benefit in preventing the progression to late AMD. Those individuals who are already on calcium supplements, for the prevention of osteoporosis, can be reassured that the higher calcium intake is unlikely to affect their AMD."

SOURCE: https://bit.ly/2WrLL8T and https://bit.ly/2V10XJN

JAMA Ophthalmol 2019.