The effect of magnesium supplementation on biochemical markers of bone metabolism or blood pressure in healthy young adult females.

OBJECTIVES: To investigate the effects of increasing Mg intakes, above the usual dietary intake, on blood pressure and on biomarkers of bone metabolism in healthy young adult females. DESIGN: A double-blind, placebo-controlled, randomised crossover Mg intervention trial. SETTING: The study was conducted in the Department of Nutrition, University College, Cork, Ireland. SUBJECTS: Twenty-six healthy (normotensive) adult females aged 20-28 y were recruited from University College, Cork. INTERVENTION: Subjects were randomly assigned to their self-selected diets (approximately 11 mmol Mg/d) or their self-selected diet with a 10 mmol/d Mg supplement as Mg(OH)2 (approximately 22 mmol Mg/d) for 28 d followed by cross-over to the alternative diet for a further 28 d. During each dietary period urines (last 3 d) and blood (morning of 27 d) were collected and blood pressure was measured on the morning of 28 d. RESULTS: Increasing Mg intake from the usual level (11 mmol/d) to 22 mmol/d for 28d increased urinary excretion of Mg by 36% and erythrocyte Mg content by 5% but had no effect on serum Mg, Ca, PTH, osteocalcin or bone-specific alkaline phosphatase (biomarkers of bone formation), urinary pyridinium crosslinks of collagen (biomarkers of bone resorption), or on blood pressure. CONCLUSION: Increasing the mean Mg intake in healthy young adult females above the usual dietary intake, which is currently above the US EAR (estimated average requirement), but below the US RDA for Mg, does not affect blood pressure or the rate of bone turnover.