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Dietary Magnesium Deficiency Induces Heart Rhythm Changes, Impairs Glucose Tolerance, and Decreases Serum Cholesterol in Post Menopausal Women

US Department of Agriculture ^a,b, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, North Dakota
^a The US Department of Agriculture, Agricultural Research Service, Northern Plains Area, is an equal opportunity/affirmative action employer, and all agency services are available without discrimination
^b Mention of a trademark or proprietary product does not constitute a guarantee or warranty by the US Department of Agriculture and does not imply its approval to the exclusion of other products that also might be suitable

Address reprint requests to: Forrest H. Nielsen, PhD, USDA, ARS, Grand Forks Human Nutrition Research Center, PO Box 9034, Grand Forks, ND, 58202-9034. E-mail: fnielsen{at}gfhnrc.ars.usda.gov

Objective: To determine whether or not dietary magnesium restriction to about 33% of the Recommended Dietary Allowance (RDA) causes changes in glucose, cholesterol and electrolyte metabolism that could lead to pathologic consequences.

Design: The length of the experiment was 136 days. Subjects were fed a basal Western-type diet that provided 4.16 mmol (101 mg) magnesium per 8.4 MJ (2000 kcal) for 78 days then replenished with magnesium by supplementing the diet with 200 mg magnesium as the gluconate per day for 58 days. If a subject exhibited adverse heart rhythm changes before 78 days of depletion were completed, she entered the repletion period early.

Setting: The metabolic research unit of the Grand Forks Human Nutrition Research Center.

Subjects: A total of 14 post menopausal women were recruited by advertisement throughout the United States. Thirteen women (ages 47 to 75 years) completed the study.

Results: During magnesium depletion, heart rhythm changes appeared in 5 women and resulted in 4 prematurely entering the magnesium repletion period (42 to 64 days of depletion instead of 78). Three women exhibited atrial fibrillation and flutter that responded quickly to magnesium supplementation. Magnesium deprivation resulted in a non-positive magnesium balance that became highly positive with magnesium repletion. Magnesium deprivation decreased red blood cell membrane magnesium, serum total cholesterol and erythrocyte superoxide dismutase concentrations, increased the urinary excretion of sodium and potassium, and increased serum glucose concentration.

Conclusions: Magnesium balance may be a suitable indicator of magnesium depletion under experimental conditions. Magnesium deficiency resulting from feeding a diet that would not be considered having an atypical menu induces heart arrhythmias, impairs glucose homeostasis, and alters cholesterol and oxidative metabolism in post menopausal women. A dietary intake of about 4.12 mmol (100 mg) Mg/8.4 MJ is inadequate for healthy adults and may result in compromised cardiovascular health and glycemic control in post menopausal women.

Key words: magnesium deficiency, magnesium balance, heart arrhythmia, glucose tolerance, cholesterol