Magnesium is intimately interlocked, biologically with calcium. In some reactions, such as the synthesis of nucleic acids and protein, calcium and magnesium are antagonistic. Magnesium is necessary for these processes, while calcium can inhibit them. Magnesium and calcium cooperate, however, in the production of adenosine triphosphate or ATP. Magnesium has been called "nature's physiological calcium channel blocker" since it appears to regulate the intracellular flow of calcium ions.
Symptoms and signs of magnesium deficiency include anorexia, nausea and vomiting, diarrhea, generalized muscle spasticity, paresthesias, confusion, tremor, focal and generalized seizures, confusion, loss of coordination, cardiac arrhythmias, laboratory abnormalities, such as hypokalemia and hypocalcemia, muscle cramps, hypertension and coronary and cerebral vasospasms. Magnesium deficiency may be found in diabetes mellitus, malabsorption syndromes, alcoholism and hyperthyroidism, among other disorders. Use of certain drugs may also lead to magnesium deficiency. These drugs include thiazide diuretics (when used for long periods of time), loop diuretics, cisplatin, amphotericin, pentamidine (when used intravenously), aminoglycosides and cyclosporine. Magnesium deficiency itself is an important cause of hypokalemia.
In addition to its use for the treatment of hypomagnesemia, magnesium is used for the treatment of certain cardiac arrhythmias, in particular torsade de pointes, and eclampsia. It is also used as a laxative and antacid. Magnesium may also have value for the prevention of osteoporosis and for the management of migraine headaches in some. There is preliminary evidence that magnesium may help some with premenstrual syndrome, type 2 diabetes mellitus and hypertension. The role of magnesium, if any, in the management of acute myocardial infarction remains controversial.
Foods rich in magnesium include unpolished grains, nuts and green vegetables. Green leafy vegetables are particularly good sources of magnesium because of their chlorophyll content. Chlorophyll is the magnesium chelate of porphyrin. Meats, starches and milk are less rich sources of magnesium. Refined and processed foods are generally magnesium-poor. The mean daily magnesium intake in the U.S. in males nine years and older is estimated to be about 323 milligrams; for females nine years and older, it is estimated to be 228 milligrams. Some surveys report lower intakes, and some believe that the dietary intake for many may be sub-optimal.
Magnesium depletion is associated with a number of cardiac arrhythmias, including atrial fibrillation, premature atrial and ventricular beats, ventricular tachycardia and ventricular fibrillation. Magnesium is effective in treating these arrhythmias in those who are magnesium deficient. Magnesium may also be effective in treating cardiac arrhythmias in those who are not magnesium deficient. This is especially true for the treatment, by magnesium, of torsade de pointes. The mechanism of the anti-arrhythmic action of magnesium is not fully understood. The anti-arrhythmic effect of magnesium may be related to its role in maintaining intracellular potassium. It may also be related to its role as a natural calcium channel blocker.
Magnesium sulfate is widely used to prevent eclamptic seizures in pregnant women with hypertension. Vasospasm in preeclampsia is thought to be a consequence of endothelial dysfunction. Magnesium has been found, both in vitro and in vivo, to increase production of the vasodilator prostacyclin. Magnesium may also protect against damage to the endothelium by reactive oxygen species. The action of magnesium sulfate in the treatment of eclampsia can be accounted for by the release of endothelial prostaglandin by magnesium, its protection against reactive oxygen species damage to the endothelium and by its possible inhibition of platelet aggregation. It may act as an anticonvulsant via neuronal calcium-channel blockade and antagonism of the glutamate N-methyl-D-aspartate (NMDA) receptor.
Some studies have reported that some populations with low dietary intake of magnesium have increased incidence of hypertension. Another study reported dietary intake of magnesium in normotensives to be significantly greater than intake in untreated hypertensive subjects. Intervention studies with magnesium therapy for hypertensives have led to conflicting results. The mechanism of the possible anti-hypertensive activity of magnesium is unclear. A possibility is that magnesium, acting in a calcium channel blocking capacity, may have a vasodilatory action.
A few studies have reported that magnesium depletion results in insulin resistance as well as impaired secretion of insulin. Insulin resistance and abnormal glucose tolerance may be accounted for, in part, by inadequate magnesium. Some studies have reported improved insulin response in elderly type 2 diabetics who received magnesium. The mechanism of the possible role of magnesium in improving glycemic control is unclear. Magnesium is a cofactor for phosphorylation reactions. Magnesium may affect insulin signal transduction. Magnesium may also alter insulin receptor binding. These are some speculative possibilities.
Intravenous magnesium has been demonstrated to have bronchodilatory activity in some with asthma. The mechanism of this activity is unclear.
The mechanism of the putative myocardial protective activity of magnesium during an acute myocardial infarction is also unclear. Speculative possibilities include magnesium's anti-arrhythmic activity, as well as its possible activity in inhibiting platelet aggregation. Magnesium's possible vasodilatory activity-via its acting as a calcium channel blocker-and possible reduction of reperfusion dysfunction are two additional speculative mechanisms for this putative activity. The mechanism of the possible anti-migraine activity is unknown.
Magnesium deficiency is associated with the pathogenesis of numerous serious disorders, notably ischemic heart disease, congestive heart failure, sudden cardiac death, cardiac arrhythmias, diabetes mellitus, pre-eclampsia/eclampsia and hypertension, among others. Treatment with supplemental magnesium is often helpful in these conditions. There is also evidence that it can be of benefit in some with osteoporosis, alcoholism, migraine, asthma, pre-menstrual syndromes, kidney stones and strokes. It may help prevent or reduce the incidence of cerebral palsy and mental retardation in early pre-term infants. There is little or no evidence to support claims that magnesium enhances athletic/exercise performance, that it is an effective antidepressant or that it is helpful in bipolar disorder.
Combinations of potassium, calcium, and magnesium supplements in hypertension.
Dietary intakes of magnesium, calcium, and potassium have each been reported to lower blood pressure, but the extent of blood pressure reduction in epidemiological studies and clinical trials has tended to be small and inconsistent. We hypothesized that combinations of these mineral supplements would lower blood pressure and that the reductions would be greater than that usually reported in studies of each cation alone. One hundred twenty-five patients 82 men and 43 women) with untreated mild or borderline hypertension were randomly assigned to daily treatment with one of the following four regimens: 60 mmol potassium and 25 mmol (1000 mg) calcium, 60 mmol potassium and 15 mmol (360 mg) magnesium, calcium and magnesium, or placebo. Standardized clinic blood pressure measurements were obtained on 3 days at baseline and after 3 and 6 months of treatment. At baseline, systolic and diastolic blood pressures (mean +/- SD) were 139 +/- 12 and 90 +/- 4 mm Hg, respectively, and dietary intakes of potassium, calcium, and magnesium were 77 +/- 32, 19 +/- 13, and 12 +/- 52 mmol/d, respectively. The mean differences (with 95% confidence intervals) of the changes in systolic and diastolic blood pressures between the treatment and placebo groups were not significant: -0.7 (-4.3 to +2.9) and -0.4 (-2.9 to +2.1) for potassium and calcium, -1.3 (-4.4 to +1.8) and 0.4 (-2.5 to +3.3) for potassium and magnesium, and +2.1 (-1.8 to +6.0) and +2.2 (-1.0 to +5.4) for calcium and magnesium. In conclusion, this trial provides little evidence of an important role of combinations of cation supplements in the treatment of mild or borderline hypertension.
Sacks-FM; Brown-LE; Appel-L; Borhani-NO; Evans-D; Whelton-P
Variations in magnesium and zinc in hypertensive patients receiving different treatments.
We studied the influence of captopril, atenolol, and verapamil on serum and intraerythrocyte concentrations of magnesium and zinc in 30 normotensive control subjects (12 men and 18 women, aged 30 to 65 years, mean +/- SD 45.76 +/- 12.15 years) and 30 patients with untreated mild or moderate essential hypertension (14 men and 16 women, aged 30 to 65 years, mean +/- SD 49.50 +/- 13.58 years). Ten each of the hypertensive patients were treated with captopril, atenolol, or verapamil. Physical examination and biochemical analyses (serum Mg and Zn) were done in all participants at baseline, and in patients after 3 and 6 months of treatment. The results were compared according to a nested design with Neumann-Keuls test. We found no significant differences between controls and patients in serum and intraerythrocyte concentrations of Zn at the start of the study, although there was a significant decrease in serum Zn in patients after 3 (P < .01) and 6 months (P < .001) of treatment, regardless of the drug used. This decrease was thought to be attributable to the zincuric effect of captopril or to dietary measures, or both. Intraerythrocyte Zn was not significantly affected by antihypertensive treatment. Serum and intraerythrocyte concentrations of magnesium were significantly lower (P < .001) in hypertensive than in normotensive subjects, and serum Mg in patients treated with verapamil was significantly lower (P < .05) than after treatment with captopril or atenolol. Serum Mg concentration was related directly with serum concentrations of high density lipoprotein cholesterol (r = 0.4043, P < .05). We conclude that supplementation with Mg may benefit patients with hypertension.
Rubio-Luengo-MA; Maldonado-Martin-A; Gil-Extremera-B; Gonzalez-Gomez-L; Luna-del-Castillo-JD
Hypertension and electrolyte therapy.
Approximately 50 million Americans are at risk for cardiovascular and cerebrovascular disease as a result of hypertension (HTN). Education and treatment programs aimed at reducing HTN have been successful in decreasing morbidity and mortality from heart disease and strokes in recent years. In addition to pharmacologic means, prevention of HTN by lifestyle modifications has become a focus of public health education. One such modification, electrolyte therapy, has been associated with HTN control and is readily available through both dietary sources and supplementary tablets. This article presents an overview of electrolyte therapy as treatment for HTN, and reviews studies of the effects of sodium, potassium, and magnesium, and their combinations as treatment to reduce blood pressure. Strategies for nurses in educating the public on the effects of electrolytes and blood pressure are also discussed.
Martinez-G; Source by: www.mdschoice.com