Short-term studies have shown that oral magnesium supplements improve endothelial function. It is less clear if this effect improves outcomes in patients with coronary artery disease (CAD). Shechter and associates compared the effect of oral magnesium with placebo on CAD outcomes by measuring exercise tolerance, exercise-induced ischemia, and quality of life.

Using a randomized, prospective, multicenter, double-blind, placebo-controlled trial enrolling 187 participants older than 20 years with stable CAD, twice-daily oral magnesium supplementation was compared with placebo. Patients continued all other medications and routine diet habits during the six-month study.

Baseline magnesium levels were similar between the two groups but increased significantly in the participants receiving magnesium supplementation. The treatment group had a significant improvement in exercise duration compared with no change in the placebo group. There was a significant decrease in exercise-induced chest pain and ST-segment depression at peak exercise in the treatment group. Most quality-of-life parameters also improved in the treatment group. There were no significant differences noted in lipid levels in either group after six months. There was no increase in adverse events in the treatment group.

The authors conclude that in a patient group already receiving near-optimal care for CAD, magnesium therapy improved cardiac exercise tolerance, exercise-induced chest pain, and quality of life. Potential mechanisms that may be responsible for this beneficial effect include improved intracellular adenosine triphosphate production, enhanced control of intracellular calcium changes, reduced systemic and pulmonary vascular resistance, reduced arteriolar tone, and mild reduction of systolic blood pressure. It also is possible that CAD may be associated with excessive magnesium loss and relative magnesium deficiency. Magnesium should be used as adjuvant therapy in patients with CAD.