What’s the Verdict on Calcium and AMD?
For years, Americans have been encouraged to consume calcium-rich foods and take a calcium supplement if they need more calcium to meet their requirements.1 Calcium has an important role in bone health. It also is necessary for the heart, muscles, and nerves to work properly.
Calcium and eye health
What about calcium’s role in eye health? Research results have been mixed. Three major studies have been published about the link between calcium and age-related macular degeneration (AMD). Two studies showed that higher calcium intake may be protective against AMD.2,3 One study showed that 800 mg of supplemental calcium may be linked to late AMD in older adults.4
Are dietary supplements right for you?
The strengths and limitations of these three studies are discussed below. In general, it is best to meet your nutrient needs by eating a wide variety of healthy foods. If you are thinking of taking a dietary supplement, it is a good idea to talk to your provider. Dietary supplements have a role in managing some diseases, but—especially at high doses—can have some health risks and may interact with other medications. Together, you and your provider can make the decision that is best for you.
Does calcium protect against AMD?
Blue Mountains Eye Study
The Blue Mountains Eye Study included 2037 adults aged 49 years or older.2 Participants had eye examinations at the beginning of the study. They were invited for follow-up examinations 5, 10, and 15 years later. Participants were asked how frequently they ate a variety of individual food items, including several calcium-rich foods, during the past year. Participants were not asked about calcium supplements.
The results of the Blue Mountains Eye Study showed that the people who ate the least dairy over the 15 years were more likely to develop late AMD than people who ate the most dairy.2 The authors speculated that dietary calcium might reduce oxidation and inflammation. They also suggested that other nutrients in dairy, such as vitamin D or vitamin B12, might protect the eyes.
Age-Related Eye Disease Study
The Age-Related Eye Disease Study was a randomized clinical trial of nutritional supplements for the treatment of AMD and cataract.3 More than 4,700 older adults were followed between 1992 and 2005. They had eye examinations twice per year. At the start of the study, participants reported on their diet and supplement use. These data were used for a secondary analysis of the relationship between calcium and AMD.
Results and limitations
Calcium was generally found to be protective, although the association between calcium and different stages of AMD was inconsistent.3 Participants who consumed the most dietary calcium were less likely to develop late AMD or geographic atrophy than people who consumed the least dietary calcium. Similarly, individuals with the highest calcium supplementation had a lower risk of neovascularization. Calcium intake was not linked to risk of large drusen.
Is calcium associated with an increased diagnosis of AMD?
NHANES cohort study
In 2015, a paper published in JAMA Ophthalmology caused controversy. The authors concluded that odds of an AMD diagnosis were increased among older individuals who consumed more than 800 mg/d of supplemental calcium.4 This conclusion was based on data from 3191 participants in the 2007-2008 National Health and Nutrition Examination Survey. Researchers analyzed self-reported supplemental calcium intake (but not dietary calcium), and correlated intake with the presence of AMD based on fundus photography.
Out of 3191 participants, 248 (7.8%) had AMD, including 220 (6.9%) with early AMD and 28 (0.9%) with late AMD.4 The participants with the highest calcium intake (≥800 mg/day) were 1.85 times more likely to be diagnosed with AMD than people who did not take calcium supplements. When analyzed by age, this association was true for people older than 68, but not those who were younger.
This study has been criticized for its small sample of individuals with AMD, the limited measure of calcium intake, and its cross-sectional design.5 The authors themselves call for additional, prospective studies to clarify this relationship.4 They do not recommend discontinuing supplemental calcium based on their results, given the known benefits of calcium supplementation for other medical conditions.
The information from these three studies raises interesting questions. However, none of the three studies described here were designed to prove cause and effect, i.e., that calcium can cause or prevent AMD. Additional research is needed before a verdict is reached. In the meantime, you and your provider can discuss whether calcium supplementation is a good idea for you.
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