Observational studies on dietary or circulating
magnesium and risk of
hypertension have reported weak-to-modest inverse associations, but have lacked measures of actual dietary uptake. Urinary
magnesium excretion, an
indicator of intestinal
magnesium absorption, may provide a better insight in this association. We examined 5511 participants aged 28 to 75 years free of
hypertension in the Prevention of Renal and Vascular End-Stage Disease (PREVEND) study, a prospective population-based cohort study. Circulating
magnesium was measured in plasma and urinary
magnesium in two 24-hour urine collections, both at baseline. Incident
hypertension was defined as blood pressure ≥140 mm Hg systolic or ≥90 mm Hg diastolic, or initiation of
antihypertensive medication. During a median follow-up of 7.6 years (interquartile range, 5.0-9.3 years), 1172 participants developed
hypertension. The median urinary
magnesium excretion was 3.8 mmol/24 hour (interquartile range, 2.9-4.8 mmol/24 hour). Urinary
magnesium excretion was associated with risk of
hypertension in an inverse log-linear fashion, and this association remained after adjustment for age, sex, body mass index, smoking status, alcohol intake, parental history of
hypertension, and urinary excretion of
sodium,
potassium, and
calcium. Each 1-unit increment in ln-transformed urinary
magnesium excretion was associated with a 21% lower risk of
hypertension after multivariable adjustment (adjusted hazard ratio, 0.79; 95% confidence interval, 0.71-0.88). No associations were observed between circulating
magnesium and risk of
hypertension. In conclusion, in this cohort of men and women, urinary
magnesium excretion was inversely associated with risk of
hypertension across the entire range of habitual dietary intake.