Serum calcium, even within normal range, is associated with blood pressure with a potential influence of calcium intake

Context: Even within the physiological range, serum calcium (sCa⁺⁺) may influence vascular tone and blood pressure (BP); however, the potential modulatory role of dietary calcium intake remains unclear. Objective: To investigate the association between sCa²⁺ and BP (including central BP) and to assess whether calcium intake affects this relationship. Methods: sCa²⁺ was measured in patients referred for suspected secondary hypertension (VerHyperReg; n = 81) and in 2 population-based cohorts: the Malmö Preventive Project (MPP; n = 18 240) and the UK Biobank (UKB; n≈330 000). Calcium intake was assessed in the Malmö Diet and Cancer Study (MDC; n = 28 098) and in a subsample of MPP participants (MPP×MDC; n = 4095). Multivariable regression models were used to analyze the associations. Results: In MPP and UKB, sCa²⁺ was positively associated with systolic and diastolic BP (even within the normal range). In VerHyperReg, sCa²⁺ was associated with central systolic BP. In the MDC, higher calcium intake was inversely associated with BP. In MPP×MDC, sCa²⁺ was positively associated with systolic BP in the lower 3 quartiles of intake, whereas this association was reversed in the highest quartile. Conclusion: Serum calcium levels within the normal range are positively associated with BP. Increased dietary calcium intake may attenuate this relationship, thus suggesting a modulatory role in BP regulation. Further investigations are warranted.