TY - JOUR T1 - Decreased magnesium status may mediate the increased cardiovascular risk associated with calcium supplementation JF - Open Heart JO - Open Heart DO - 10.1136/openhrt-2017-000617 VL - 4 IS - 1 SP - e000617 AU - James J DiNicolantonio AU - Mark F McCarty AU - James H O’Keefe Y1 - 2017/05/01 UR - http://openheart.bmj.com/content/4/1/e000617.abstract N2 - A meta-analyses of randomised controlled studies of calcium supplementation (some including concurrent modest intakes of vitamin D) has observed a modest increase in risk for vascular events in the calcium-supplemented subjects.1 Some recent observational epidemiology in prospective cohorts has also linked supplemental calcium to increased vascular risk.2–4 Yet, rather perplexingly, relatively high dietary intakes of calcium have been associated with cardiovascular protection, or a neutral outcome in this regard.2 3 5 6 Moreover, there are theoretical grounds for expecting that superior calcium nutrition could be protective for vascular health. High-calcium diets decrease secretion of parathyroid hormone; even mild secondary hyperparathyroidism, common in the elderly, is suspected to increase vascular risk.7 8 A high calcium intake also tends to suppress absorption of dietary phosphate by forming an insoluble complex with it; emerging data suggest that high phosphate intakes may increase cardiovascular risk, even in those with normal renal function.9 High calcium intakes have not been found to correlate with increased risk for vascular calcification.10 The acute vascular impact of the modest rise in serum calcium following a bolus oral dose of calcium citrate has been studied; relative to placebo, arterial stiffness declined and myocardial perfusion increased in the calcium group.11 However, the diurnal decline in blood pressure was not as high in calcium-supplemented subjects and a coagulation index (thromboelastography) increased.12 What could explain the increased risk for vascular events associated specifically with calcium supplementation in some controlled studies? Even if subsequent analyses fail to confirm a net negative impact of calcium supplementation on vascular health—this issue is hotly debated and cannot be considered resolved5 13–15—the fact that calcium could be expected to protect the vasculature for certain reasons suggests that it must be exerting some countervailing negative effect even if its … ER -