|Milne, David - USDA RETIRED|
|Gallagher, Sandra - UNIV NORTH DAKOTA|
|Johnson, Luann - UNIV NORTH DAKOTA|
|Hoverson, Bonita - UNIV NORTH DAKOTA|
Submitted to: Magnesium Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 19, 2007
Publication Date: April 1, 2007
Repository URL: http://www.john-libbey-eurotext.fr
Citation: Nielsen, F.H., Milne, D.B., Gallagher, S., Johnson, L.K., Hoverson, B. 2007. Moderate magnesium deprivation results in calcium retention and altered potassium and phosphorus excretion by postmenopausal women. Magnesium Research. 20(1):19-31. Interpretive Summary: Epidemiological surveys, supplementation trials, and animal studies have suggested that magnesium deficiency may be a significant factor in some human disorders including osteoporosis, ischemic heart disease, high blood pressure, stroke, migraine headaches, diabetes, decreased pain tolerance, and neurological disturbances. However, experiments involving humans consuming plausible low-magnesium diets have not been particularly successful in providing evidence that magnesium deficiency is a primary factor for any of these disorders. Thus, an experiment was conducted with postmenopausal women (11 completed the experiment as designed) that were fed diets providing about 107 mg and 327 milligrams of magnesium per day for 72 days each. Magnesium balance was non-positive during low-magnesium period and highly positive during the high-magnesium period. Also, magnesium in the membranes of red blood cells decreased during the low-magnesium dietary period. These findings indicate that the women were becoming magnesium-deficient when they were fed the low-magnesium diet. The moderate magnesium depletion achieved in this experiment increased calcium retention by apparently increasing soft tissue accumulation through increasing the amount found inside cells. This increased cellular calcium may lead to increased oxidative stress and cell activation molecules that can induce undesirable changes in cardiovascular, bone and brain health. The findings indicate that 107 mg of magnesium per day is inadequate for postmenopausal women. Because the usual magnesium intake of 5% of all women over age 19 y in the United States is just slightly more than this amount (128 milligrams per day), magnesium deficiency may be a significant factor compromising cardiovascular, bone, and neurological health.
Technical Abstract: An experiment was performed to confirm that naturally occurring deficient intakes of magnesium resulting in non-positive magnesium balance increases calcium retention and alters the metabolism of other minerals (sodium, potassium, phosphorus) involved in cellular ionic balance, and to assess possible indicators of magnesium deficiency. A total of 15 postmenopausal Caucasian women were recruited by advertisement throughout the United States to participate in the study. Eleven women (ages 49 to 71 yr) completed the study as designed. The women were housed in the metabolic research unit of the Grand Forks Human Nutrition Research Center. The women were fed a basal Western-type diet that resulted in a mean intake of 4.40 mmol (107 mg) magnesium/d. After being fed the basal diet supplemented with 9.05 mmol (220 mg) magnesium/d for 18 d (equilibration), the women were assigned to one of two groups in an experiment with a double-blind, crossover design. One group was fed the basal diet and supplemented with a lactose placebo while the other group continued consuming the basal diet supplemented with 9.05 mmol magnesium/d for 72 d, then the groups switched diets for another 72 d. Magnesium was supplemented as magnesium gluconate. Magnesium deprivation resulted in a non-positive magnesium balance (-0.21 mmol or -5 mg/d) that was highly positive during magnesium supplementation (+2.22 mmol or +54 mg/d). Magnesium deprivation decreased red blood cell membrane magnesium (2.5 vs 2.7 nmol or 0.061 vs 0.065 µg/mg protein; P less than or equal to 0.05). Magnesium deprivation did not significantly affect lymphocyte, platelet, serum albumin-bound and serum ultrafiltrable magnesium concentrations. Red blood cell and serum magnesium concentration changes were affected by the sequence of the diets. Magnesium deprivation increased calcium balance (+0.82 mmol or +35mg/d vs -0.02 or -1 mg/d; p less than or equal to 0.009); decreased the fecal excretion of phosphorus (28.9% vs 32.3% of intake; p less than or equal to 0.0001); increased the urinary excretion of phosphorus (73.4% vs 71.0%; p less than or equal to 0.003); and decreased the urinary excretion of potassium (40.4 mmol or 1.58 g/d vs 41.9 mmol or 1.64 g/d; p less than or equal to 0.04). The findings indicate that non-positive magnesium balance and decreased red blood cell membrane magnesium concentration apparently are indicators of magnesium depletion under experimental conditions. Moderate magnesium deprivation achieved through diet alone results in increased calcium retention by apparently increasing soft tissue accumulation and intracellular calcium. Magnesium deprivation also alters phosphorus and potassium excretion. The changes indicate that an intake of 4.40 mmol (107 mg) magnesium/d is inadequate for postmenopausal women because of changes in intracellular calcium that may lead to pathophysiological conditions.