Effect of Magnesium Supplementation on Elevated Systolic Blood Pressure

Inclusion Criteria: * Self-report of systolic blood pressure 125-159 mmHg * Measured seated systolic blood pressure 130-159 mmHg at screening visit * Body mass index less than 40 kg/m2 * Total magnesium intake from supplements of no more than 100 mg/day * Willing to maintain current diet and supplement use patterns during the 12-week intervention period Exclusion Criteria: * Measured seated diastolic blood pressure 100 mmHg or greater at screening visit * Antacid or laxative use 4 times/week or more within the past 3 months * History of cardiovascular disease (myocardial infarction, stroke, revascularization \[coronary artery bypass graft or percutaneous transluminal coronary angioplasty\], or angina pectoris) * History of invasive cancer diagnosed within the last 5 years (non-melanoma skin cancer permitted) * History of type 1 or 2 diabetes * History of renal disease * History of kidney failure * History of dialysis * History of pancreatitis * History of inflammatory bowel disease * History of hypermagnesemia * Women who are pregnant, nursing, or intend to become pregnant during the period of treatment * Plan to relocate out of Boston area within the next year * Unwillingness and/or inability to swallow 4 pills per day * Inability to provide written informed consent