Dear Julie,

In last week’s wellness spotlight, we highlighted the mineral magnesium. In this week’s spotlight, we will highlight calcium and a new study published March 21, 2019 in JAMA that looked at the association of dietary and supplementary calcium intake with age-related macular degeneration.

Calcium plays a key role in imparting strength to bones and teeth. It is also involved in muscle contraction and glycogen metabolism. It is needed for muscle, heart, and digestive cell messaging systems. Adequate levels also support blood clotting, but calcium can be problematic when supplemented in excess if it decreases tissue levels of magnesium. For this reason and also because of the fact that magnesium nutritional status is often marginal or low, calcium and magnesium are often supplemented together. Many practitioners administer calcium and magnesium in a ratio approximating 2:1, whereas others prefer a ratio closer to 1:1 and there is virtually no research investigating the optimal ratio of these minerals.

There has been some controversy in the literature in regards to calcium supplementation and myocardial infarction. In a meta-analysis of 7 randomized controlled trials that excluded self-reported outcomes and included only those outcomes verified by clinical review, hospital discharge record, or death certificate, calcium supplementation was associated with an 8% increase in MI incidence (p=0.32). (Lewis et al. The effects of calcium supplementation on verified coronary heart disease hospitalization and death in postmenopausal women:a collaborative meta-analysis of randomized controlled trial. J Bone Miner Res 2015;30:165-175). If calcium supplementation does produce an increase in MI risk, the mechanism might be calcium-induced depletion of magnesium, which is an important cardioprotective nutrient. Giving magnesium along with calcium might therefore prevent any adverse effect of calcium on the cardiovascular system.

There has also been some controversy in the literature in regards to calcium supplementation and AMD. In 2015, a study was published in JAMA of a cross-sectional analysis of the National Health and Nutrition Examination Survey that showed that self-reported supplementary calcium consumption is associated with an increased prevalence of AMD. (Kakigi et al. Self-reported calcium supplementation and age-related macular degeneration. JAMA Ophthalmol. 2015;133(7):746-754). In contrast however, the Blue Mountains Eye Study, which involved 2037 participants with follow-up of 15 years reported an association between the development of late AMD in patients with a low dietary intake of calcium. (Gopinath et al. Consumption of dairy products and the 15-year incidence of age-related macular degeneration. Br J Nutr. 2014;111(9):1673-1679). In keeping with results from the Blue Mountain Eye Study, in a study recently published in JAMA Ophthalmology, Tisdale et al performed a secondary analysis of the data of 4751 AREDS participants with follow-up over 10 years and reported the association of higher intake of calcium with a reduced incidence of late AMD (geographic atrophy and neovascular AMD). (Tisdale et al. Age-Related Eye Disease Study Research Group. Association of dietary and supplementary calcium intake with age-related macular degeneration: Age-Related Eye Disease Study report 39. [published online March 21, 2019]. JAMA Ophthalmol. doi:10.1001/jamaophthalmol. 2019.0292). The strengths of the study by Tisdale et al are clear, including a large number of participants, long-term follow-up, and standardized AMD grading from stereoscopic fundus photographs. There are nonetheless limitations even in this study that should be considered before clinicians alter the management of patients with AMD, because these associations cannot indicate causality.

https://jamanetwork.com/journals/jamaophthalmology/article-abstract/2728258

For now, perhaps the most sensible approach is to conclude that the evidence to date suggests 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 based on these associations. Individuals who are already taking calcium supplements for the prevention of osteoporosis can be reassured that the higher calcium intake is unlikely to affect their AMD. However, because these findings are associations, they should be viewed as hypothesis-generating findings, and a randomized clinical trial would be needed to determine if a cause and effect association of taking calcium supplements and reducing the chance of developing late AMD exists.

Have you registered for the upcoming Nutrition and the Eye XII Symposium?  April 13-14, 2019

A 12 – hour conference exploring the emerging sciences of “energy medicine,” photo-biomodulation (PBM) and clinical data using new commercial devices. Our faculty reveal the role of light in the pathogenesis of myopia and present evidence that exposure of ocular and dermal tissue to low energy photon irradiation in the far-red (FR) to near-infrared (NIR), can restore the function of damaged mitochondria, upregulate the production of cyto-protective factors and prevent cell death.