Associations of calcium and magnesium intakes and their intake ratio with albuminuria in middle-aged and older adults

Calcium and magnesium both work together and against each other by sharing homeostatic regulatory systems in the kidneys. Previous studies suggested that these minerals and their intake ratio were associated with chronic health conditions such as cardiovascular disease. Our objective was to investigate the association of calcium and magnesium intake and their intake ratio with albuminuria. This cross-sectional study analyzed data from a Japanese community-based cohort comprising 6,849 individuals aged ≥40 years (mean age 68.8 years, 51.3% women). Energy-adjusted dietary intake of calcium and magnesium and the calcium-to-magnesium intake ratio were derived from a validated food frequency questionnaire. The outcome was spot urinary albumin-to-creatinine ratio (ACR, mg/g). Linear and logistic regression analyses were performed with adjustments for potential confounders. The analytic population had 1.65 and 73.5 mL/min/1.73 m2 as median intake ratio and estimated glomerular filtration rate, respectively. In multivariable linear regression analysis, lower intakes of calcium and magnesium were associated with the log-transformed ACR but, after mutual adjustment, only calcium intake was independently associated with the ACR (regression coefficient -0.084; 95%CI, -0.149, -0.019). A lower intake ratio was associated with the log-transformed ACR (regression coefficient, -0.085; 95%CI, -0.150, -0.021). These associations were evident overall and in male participants. Although magnesium intake was associated with albuminuria only before accounting for calcium intake, calcium intake and calcium-to-magnesium intake ratio demonstrated robust associations. Our findings support that the importance of calcium intake and its balancing with magnesium might extend to kidney health, especially albuminuria.