Nutritional magnesium supplementation does not change blood pressure nor serum or muscle potassium and magnesium in untreated hypertension. A double-blind crossover study.

The aim of this study was to evaluate if a nutritional dose of magnesium given orally changes the blood pressure in untreated hypertensive patients and if orally-given magnesium had any influence on serum and muscle magnesium and potassium. A randomized, double-blind crossover study design was followed with magnesium 15 mmol/day or placebo treatment for two months. Thirty-nine patients aged 20-59 years, were treated. Samples for magnesium and potassium in blood, muscle and urine were taken at entry time, after two months (crossover time) and after four months (end of study). Systolic and diastolic supine and standing blood pressures were measured at the same times. No significant change in blood pressure, serum or muscle concentrations of electrolytes were observed on magnesium treatment. Urine magnesium rose significantly on magnesium, and it decreased significantly on placebo. Therefore results suggest that 15 mmol magnesium/day, given to untreated mild-to-moderate hypertensives does not alter blood pressure nor the concentrations of magnesium and potassium in serum and muscle, in patients with normal magnesium turnover.