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Submitted to: Magnesium Research
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/20/2004 Publication Date: 9/1/2004 Citation: Nielsen, F.H. 2004. The alteration of magnesium, calcium and phosphorus metabolism by dietary magnesium deprivation in postmenopausal women is not affected by dietary boron deprivation. Magnesium Research. 17(3):197-210. Interpretive Summary: Whether inadequate intakes of magnesium by individuals not exposed to conditions that negatively affect magnesium metabolism is a practical nutritional concern is controversial. Human studies using short periods of dietary magnesium deprivation or very severe magnesium deprivation (use of liquid semi-purified diets) have caused some experts to conclude that a dietary deficiency of magnesium of a severity sufficient to provoke pathologic change is rare. Based on epidemiological studies and animal models, other magnesium experts have concluded that long term inadequate intakes of magnesium occur frequently and result in various pathological consequences including cardiovascular, bone, and psychiatric disorders. Moreover, some human and animal studies suggest that a low boron intake can exacerbate magnesium deficiency. The controversy about magnesium deficiency indicated a need for a controlled basic metabolic unit study using healthy people to determine whether a realistic inadequate intake of magnesium for several weeks would result in physiological and biochemical changes that could result in pathologic consequences. This report describes such a study. Magnesium balance, which was positive when dietary magnesium was 318 mg/d, became negative when dietary magnesium was 118 mg/d. The magnesium deprivation decreased urinary calcium and potassium excretion and serum cholesterol concentration, and increased urinary phosphorus excretion and the concentration of serum vitamin D in an active form. One woman exhibited abnormal heart rhythm after consuming the low-magnesium diet for 72 days. A low dietary boron intake did not exacerbate the effects of magnesium deprivation. The findings indicate that consuming an ordinary diet low in magnesium can result in negative magnesium balance leading to a deficiency that can undesirably affect calcium, potassium, and cholesterol metabolism. Technical Abstract: A study with human volunteers was conducted to test the hypotheses that naturally occurring inadequate intakes of magnesium induce negative magnesium balance and undesirable changes in calcium metabolism variables, and that these changes are influenced by dietary boron. Diets composed of ordinary Western foods providing approximately 118 and 318 mg Mg/d and approximately 0.25 and 3.25 mg B/d were fed in a double-blind Latin square design to 13 healthy, post menopausal Caucasian women (aged 50-78 years) living in a metabolic unit. Magnesium balance, which was positive when dietary magnesium was 318 mg/d, became negative when dietary magnesium was 118 mg/d. Magnesium deprivation decreased urinary calcium excretion, and significantly increased calcium balance when balance data analyzed came from all collections during the 42-day periods, but the apparent increase was not significant when data from the last 24 days of each period was compared. Urinary phosphorus excretion was increased, but fecal phosphorus excretion was decreased, thus phosphorus balance was not significantly affected, by magnesium deprivation. Magnesium deprivation did not affect manganese or zinc balance, but the balance data indicated that 700 mg of calcium, 1.0 mg of manganese, and 10 mg of zinc were adequate for post menopausal women to maintain balance of these minerals. Boron deprivation did not affect any measures of magnesium, calcium, phosphorus, manganese or zinc metabolism. Boron deprivation increased but magnesium deprivation decreased urinary potassium excretion. Magnesium deprivation increased serum 25-hydroxycholecalciferol and decreased serum total cholesterol concentrations. Boron supplementation decreased serum 17ß-estradiol, and progesterone when dietary magnesium was low. The dietary treatments did not affect serum calcitonin, parathyroid hormone, osteocalcin or alkaline phosphatase concentrations. One woman placed on consecutive magnesium-low dietary periods exhibited heart ventricular ectopy after consuming the magnesium-low diet for 72 days; the ectopy disappeared upon consuming the magnesium-adequate diet. The findings indicated that consuming an ordinary diet deficient in magnesium, resulting in negative magnesium balance, can affect calcium, potassium, and cholesterol metabolism. Dietary boron did not have an obvious effect on the response to magnesium deprivation. |
