Perspective: Characterization of Dietary Supplements Containing Calcium and Magnesium and Their Respective Ratio-Is a Rising Ratio a Cause for Concern?

Low magnesium intakes coupled with high calcium intakes and high calcium-to-magnesium (Ca:Mg) intake ratios have been associated with increased risk for multiple chronic conditions such as cardiovascular disease and metabolic syndrome, as well as some cancers (colorectal, prostate, esophageal), and total mortality. A high dietary Ca:Mg ratio (>2.60) may affect body magnesium status while, on the other hand, high intakes of magnesium could adversely impact individuals with an exceedingly low dietary Ca:Mg ratio (<1.70). Thus, a Ca:Mg ratio range of 1.70-2.60 (weight to weight) has been proposed as an optimum range. Data from NHANES surveys have shown the mean Ca:Mg intake ratio from foods alone for US adults has been >3.00 since 2000. One-third of Americans consume a magnesium supplement with a mean dose of 146 mg/d, and 35% of Americans consume a calcium supplement with a mean dose of 479 mg/d. Our review of Ca:Mg ratios in dietary supplements sold in the United States and listed in NIH's Dietary Supplement Label Database (DSLD) found a mean ratio of 2.90 across all calcium- and magnesium-containing products, with differences by product form. The ratios ranged from a low of 0.10 in liquid products to a high of 48.5 in powder products. Thirty-one percent of products fell below, 40.5% fell within, and 28.3% fell above the ratio range of 1.70-2.60. Our findings of calculated Ca:Mg ratios from dietary supplements coupled with food-intake data suggest that, in individuals with high calcium intakes from diet and/or supplements, magnesium supplementation may be warranted to establish a more favorable dietary Ca:Mg ratio in their total diet. Additional research may provide greater insight into whether the Ca:Mg ratio is a biomarker of interest for moderating chronic disease and which population groups may derive benefit from moderating that ratio. Published by Oxford University Press on behalf of the American Society for Nutrition 2020.