Magnesium (Mg) is an essential trace mineral involved in over 300 metabolic reactions including cellular energy generation, nucleic acid production (DNA, RNA), and protein synthesis.
Thirty to 50% of dietary magnesium is absorbed in the small intestine. Excess intake of certain dietary components, such as calcium, phosphate, oxalate, and phytate interfere with magnesium absorption.
Typical daily intake of magnesium in the United States is about 300 mg.
Magnesium (Mg+2) is the most abundant intracellular divalent cation.
The adult human body contains approximately 25 grams of magnesium.
Approximately 50-60% of magnesium in the body is in bone, with the remainder in muscle and soft tissues.1
Certain magnesium salts are used as laxatives and antacids.
Magnesium is involved in many cellular functions, especially those critical to energy production, transport of potassium and calcium ions, modulation of signal transduction, and cell proliferation.
Magnesium is essential for muscle contraction, nerve conduction, membrane integrity, and vascular tone.
Magnesium is closely associated with calcium in the body, as magnesium helps regulate intracellular flow of calcium ions.
The kidney regulates excretion of magnesium. Cellular availability of magnesium is also regulated by the gastrointestinal tract and bone.
Magnesium is directly involved in bone metabolism. It is necessary for formation of bone crystals and the organic matrix of bones. Magnesium effects numerous hormones (parathyroid hormone, vitamin D, calcitonin) that help regulate bone metabolism.
Magnesium has an important role in insulin metabolism. About 30% of diabetic patients show hypomagnesemia.
Males 9 to 13 years 14 to 18 years 19 to 30 years 31+ years
240 410 400 420
350 350 350 350
Females 9 to 13 years 14 to 18 years 19 to 30 years 31+ years
240 360 310 320
350 350 350 350
Pregnancy <= 18 years 19 to 30 years 31 to 50 years
400 350 360
350 350 350
Lactation <= 18 years 19 to 30 years 31 to 50 years
360 310 320
350 350 350
*Values are Adequate Intakes (AI), all others are Recommended Dietary Allowances. The UL's for magnesium represent intake from a pharmacological agent only and do not include intake from food and water. 6
*Not determinable due to
lack of adverse effects in this age group and concern with regard to lack of
ability to handle excess amounts.
The newest data regarding magnesium requirements indicate that adult men and women require approximately 165 mg elemental magnesium per day to balance magnesium intake with excretion.12
Magnesium intake has decreased over the years, especially in the western world. The elderly are at particular risk for magnesium deficiency. Magnesium deficiency is also not uncommon among the general population.
Signs/symptoms of magnesium deficiency include: fatigue, confusion, irritability, weakness, hypertension, heart disturbance, loss of appetite, insomnia, nausea, vomiting, diarrhea, problems with nerve conduction, and problems with muscle contraction.
Moderate to severe magnesium deficiency can lead to specific biochemical abnormalities such as hypocalcemia and vitamin D resistance in humans.
Magnesium deficiency may cause or worsen arrhythmia and myocardial infarction.
Magnesium depletion has been associated with decreased bone growth and bone strength, certain cardiac arrhythymias, pre-eclampsia and eclampsia, hypertension, and insulin resistance.
Magnesium deficiency is associated with certain cardiac disorders, diabetes mellitus, malabsorption syndromes, alcoholism, hyperthyroidism, and diarrhea.
Unprocessed grains and nuts have the highest magnesium nutrient density, ranging from 200 to 800 mg of magnesium per 100 g product. Other good sources of magnesium are legumes and green leafy vegetables, because of their chlorophyll content. Seafood, chocolate and cocoa are also good sources of magnesium.
According to recent data on magnesium (Mg) intake among U.S. adults, certain populations are not consuming adequate amounts of this mineral. Researchers analyzed 24-hour intake records from 4,257 participants aged 20 years or older from NHANES 1999-2000. Significant racial, ethnic, and gender-based differences in magnesium intake were found. Caucasian and Mexican American men and women had significantly higher magnesium intake than African Americans. Men had significantly higher magnesium intake than women. Those who consumed vitamin and mineral supplements (Caucasian men and women and African American men) had significantly higher dietary Mg intakes than those who did not consume supplements. A considerable number of U.S. adults fail to consume adequate dietary Mg and may benefit from Mg supplementation.
Magnesium salts such as those contained in antacids may decrease bioavailability and absorption of digoxin (Lanoxin), a cardiac agent. Doses should be spaced as far apart as possible from doses of magnesium or magnesium-containing antacids.
Gastrointestinal absorption and serum concentrations of antibiotics may be decreased by concurrent administration of magnesium salts. Decreased absorption may reduce efficacy of the antibiotics. Doses of tetracycline, aminoquinolone, and other antibiotics should be spaced one to two hours from doses of magnesium.
Cisplatin (Platinol) is a chemotherapeutic agent used with other drugs to treat various cancers. Cisplatin-induced kidney damage leads to loss of minerals from the body, including magnesium. Supplementation should be supervised by a physician or pharmacist.
Loop diuretics such as furosemide, bumetanide, and thiazide, may cause cellular magnesium depletion.
Magnesium-containing antacids administered concomitantly with dicumarol (Coumadin, Miradon), an anticoagulant agent, increase absorption of dicumarol.
Magnesium salts may decrease absorption of nitrofurantoin (Furadantin), an antimicrobial agent used to treat acute uncomplicated urinary tract infections.
Magnesium salts reduce gastrointestinal absorption of penicillamine (Cuprimine), an agent used for copper toxicity.
Concomitant administration of magnesium-containing antacids and chlordiazepoxide (Librium), an anxiolytic agent, decreases the rate of absorption of this drug.
Oral magnesium therapy, exercise heart rate, exercise tolerance, and myocardial function in coronary artery disease patients.
To investigate the effect of oral magnesium supplementation on exercise dependent heart rate in people with coronary artery disease (CAD), 53 male patients with stable CAD were enrolled in a double-blind, placebo-controlled trial. Twenty-eight of the volunteers received a daily supplement of 30 mmol elemental magnesium (730 mg) and 25 volunteers received a daily placebo for six months. Magnesium supplementation increased intracellular magnesium (32.7+/-2.5 v 35.6+/-2.1 mEq/l, p<0.001) compared to placebo (33.1+/-31.9 v 33.8+/-2.0 mEq/l, NS). Magnesium also improved exercise tolerance, VO2 max (28.3+/-6.2 v 30.6+/-7.1 ml/kg/min, p<0.001; 29.3+/-5.4 v 29.6+/-5.2 ml/kg/min, NS), factor k (-0.298+/-0.242 v -0.208+/-0.260, p<0.05; -0.269+/-0.336 v -0.272+/-0.335, NS), and left ventricular ejection fraction (58+/-11 v 67+/-10%, p<0.001; 55+/-11 v 54+/-12%, NS). These results indicate that magnesium supplementation improves exercise tolerance and left ventricular function in people with CAD.14
Dietary magnesium intake and risk of cardiovascular disease among women.
The hypothesis that increased magnesium intake reduces risk for cardiovascular disease was tested in a large prospective study with 39,876 female healthcare workers. Women between 39 and 89 years of age were enrolled in the study and followed with questionnaires for ten years (median). At the end of the study, no association between magnesium intake and cardiovascular disease was found. A modest inverse association between magnesium and stroke was evident. Further studies including clinical trials are necessary.15
The effect of magnesium supplementation on blood pressure: a meta-analysis of randomized clinical trials.
A meta-analysis of randomized trials was performed to test the effects of magnesium (Mg) supplementation on blood pressure (BP). Random effects model and meta-regression methods were used to pool study results from 20 trials meeting inclusion criteria, as well as to determine dose-response relationship of Mg to BP. The studies included 1,220 participants and doses of supplemental Mg ranged from 10-40 mmol/day (240-960 mg/day) (median = 15.4 mmol/day or 370 mg/day). Mg supplementation resulted only in a small reduction in BP, however, there was a dose-dependent effect of Mg for each 10 mmol/day increase in Mg (i.e. reduction of 4.3 mmHg systolic BP and 2.3 mmHg diastolic BP). Meta-analysis showed dose-dependent reductions in BP from Mg supplementation. To confirm this relationship, further controlled trials are needed with supplemental Mg. 11
Oral magnesium supplementation reduces ambulatory blood pressure in patients with mild hypertension.
A twelve-week trial investigated magnesium supplements for mild hypertension. Forty-eight people with mild hypertension participated in the trial. All participants were instructed to follow lifestyle modifications and half were also assigned to receive 600 mg magnesium pidolate daily. Statistically significant reductions in mean 24-h systolic and diastolic BP levels were observed (-5.6 +/- 2.7 vs. -1.3 +/- 2.4 mm Hg, P<0.001 and -2.8 +/- 1.8 vs. -1 +/- 1.2 mm Hg, P=0.002, respectively) compared to control, including daytime and nighttime periods. Serum and urinary Mg2+ levels were significantly increased in the group supplemented with Mg2+; intracellular Mg2+ and K+ levels increased and Ca2+ and Na+ decreased with Mg2+ supplementation. The results of this study suggest that magnesium supplements may help to improve blood pressure for people with mild hypertension. 18
Short-term oral magnesium supplemtation suppresses bone turnover in postmenopausal osteoporotic women.
In an age-matched case-control study, the effects of magnesium supplements on bone turnover were investigated. Twenty postmenopausal women participated in the one month trial. Ten consumed daily magnesium citrate supplements (1,830 mg/day) while ten age-matched postmenopausal women participated as the control group. Within the supplemented group, a significant decrease in serum iPTH levels (p<0.05), a significant increase in serum osteocalcin levels (p<0.001), and a significant decrease in urinary deoxypyridinoline levels (p<0.001). These results suggest that magnesium supplements reduce bone turnover in postmenopausal women. 20
Magnesium intake from food and supplements is associated with bone mineral density in healthy older white subjects.
The influence of magnesium intake on bone mineral density was assessed in an epidemiological study. Two-thousand-thirty-eight Caucasian and African American men and women between 70 and 79 years of age were enrolled in the study. Bone mineral density was assessed by densitometry and magnesium intake was determined from a semi-quantitative food frequency questionnaire which included a supplement and medication questionnaire. Magnesium intake was positively associated with bone mineral density in Caucasian but not African American elderly subjects (P=0.05 for men and P=0.005 for women). The authors suggest that this significant difference may be due to variations in bone metabolism and maintenance or in food reporting. When comparing the highest quintile to the lowest quintile of magnesium intake, bone mineral density was 0.04 g/cm2 higher in white women and 0.02 g/cm2 higher in white men.These data suggest that magnesium supplements may be beneficial for elderly Caucasian men and women. 21
Comparison of the effects of vitamins and/or mineral supplementation on glomerular and tubular dysfunction in type 2 diabetes.
A randomized, double-blind, placebo-controlled clinical trial investigated the effects of vitamin and mineral supplements on renal function for people with type 2 diabetes. Sixty-two people with type 2 diabetes enrolled in a three month supplementation study and were randomly assigned to receive 200 mg magnesium and 30 mg zinc (minerals), 200 mg vitamin C and 100 IU vitamin E (vitamins), both of the above supplements, or a placebo. After three months of supplementation, both the vitamin supplement and the combined vitamin and mineral supplements decreased urinary albumin excretion (P=0.034 and P=0.005, respectively). The combined vitamin and mineral supplements also decreased serum fasting glucose (P=0.035) and malondialdehyde concentrations (P=0.004), and increased serum HDL cholesterol and apolipoprotein A1 concentrations (P=0.019). Blood pressures were also significantly decreased in the combined vitamin and mineral supplemented group: systolic (P=0.008), diastolic (P=0.017), and mean blood pressure (P=0.009). The combined vitamin and mineral supplements improved glomerular but not tubular renal function in this study.26
Effect of oral magnesium supplementation on the lipid profile and blood glucose of patients with type 2 diabetes mellitus.
A study compared serum magnesium (Mg) concentrations in diabetic patients with those of non-diabetic controls, while assessing efficacy of oral Mg supplementation for improvement of lipid profile and blood glucose. Forty patients with type 2 diabetes and 54 non-diabetic patients participated in the study. Blood glucose, serum lipid and Mg concentrations were taken at baseline for all subjects. The diabetic patients were supplemented with 600 mg of Mg oxide daily and all subjects were re-evaluated every four weeks during the 12 week period. Mean serum Mg was lower in the diabetic group than in the control group at baseline (1.44 +/- 0.48 mg/dl Vs 2.29 +/- 0.33 mg/dl; p<0.001). Following 4 to 8 weeks of Mg supplementation a significant decrease in total cholesterol, LDL cholesterol and triglycerides and an increase in HDL cholesterol was observed. The improvements in blood lipid concentrations continued until the end of the study (12 weeks). No change in fasting postprandial blood glucose concentrations occurred. Magnesium supplementation positively influenced the lipid profile of diabetic patients. No beneficial effect on glucose concentrations was noted.16
Oral magnesium supplementation improves insulin sensitivity and metabolic control in type 2 diabetes subjects: a randomized double-blind controlled trial.
A study was conducted to determine whether oral magnesium (Mg) supplementation improved insulin sensitivity and metabolic control in 63 patients with type 2 diabetes and low serum Mg concentrations. Diabetic patients were treated with 50 mL magnesium chloride (MgCl2) solution (containing 50 g MgCl2 per 1,000 mL solution) or placebo daily for 16 weeks. Insulin resistance was measured by homeostasis model assessment for insulin resistance (HOMA-IR) and metabolic control was measured by glucose and HbA1c parameters. Subjects receiving Mg supplementation had a significantly higher serum Mg concentration (p=0.02), lower HOMA-IR index (p=0.005), lower fasting glucose levels (p=0.01), and lower HbA1c (p=0.04). Results of this study indicate that oral Mg supplementation restored serum Mg and improved insulin sensitivity and metabolic control in patients with type 2 diabetes with decreased serum Mg concentrations. 17
Oral magnesium supplementation improves insulin sensitivity in non-diabetic subjects with insulin resistance. A double-blind placebo-controlled randomized trial.
The efficacy of daily magnesium chloride (MgCl2, 2.5 g) supplementation on insulin resistance in non-diabetic people with hypomagnesemia was investigated in a randomized, double-blind, placebo-controlled trial. Sixty volunteers were randomly assigned to receive magnesium chloride or a placebo daily for three months. Magnesium supplementation significantly increased serum magnesium concentration during the trial (0.61 +/- 0.08 to 0.81 +/- 0.08 mmol/l, p<0.0001). Magnesium supplementation also improved insulin resistance (reduced HOMA-IR index 4.6 +/- 2.8 to 2.6 +/- 1.1, p<0.0001). These data suggest that magnesium supplements may improve insulin resistance for people with hypomagnesemia.25
It has been suggested that low serum magnesium (Mg) concentrations are related to diabetes mellitus (DM) and high blood pressure. Metabolic syndrome (MS) is defined as a cluster of risk factors (dyslipidemia, insulin resistance, obesity, elevated blood pressure) that are primarily associated with coronary heart disease. A cross-sectional, population-based study compared 192 individuals with MS to 384 control subjects free of disease. Low serum Mg concentrations were identified in 65% of subjects with MS and in less than 5% of subjects without MS (p=0.00001). A strong independent relationship existed between low serum Mg concentrations and subjects with MS. Dyslipidemia and high blood pressure were strongly associated with low serum Mg concentrations.19
A combination of riboflavin, magnesium, and feverfew for migraine prophylaxis: a randomized trial.
A randomized, double-blind, placebo-controlled trial investigated the efficacy of a riboflavin, magnesium, and feverfew supplement for prevention of migraines. Forty-nine subjects completed the study; subjects were randomly assigned to receive a daily supplement containing 400 mg riboflavin, 300 mg magnesium, and 100 mg feverfew or a placebo containing 25 mg riboflavin for three months. At the end of the trial, both groups demonstrated a significant reduction in number of migraines, migraine days, and migraine index compared to baseline. There were no significant differences between the two groups. These results are in conflict with previous studies and require further investigation.28
Oral magnesium oxide prophylaxis of frequent migrainous headache in children: a randomized, double-blind, placebo-controlled trial.
A study was conducted to assess whether oral magnesium (as MgO) supplementation affects frequency and severity of migraine headaches in children. Children between the ages of 3 and 17, reporting a history of at least weekly, moderate-to-severe headaches were recruited for the study. Subjects were randomized to receive either an oral magnesium oxide supplement (9 mg/kg/BW) in 3 divided doses with food (n=42), or placebo (n=44) for 16 weeks. A significant decrease in headache frequency over time was found in the Mg supplemented group (p=0.0037), but not in the placebo group (p=0.086). The Mg supplemented group experienced significantly lower headache severity versus placebo (p=0.0029). These results suggested that supplemental Mg led to significantly fewer headache days, however, additional research with more subjects is needed to confirm results.22
Urinary magnesium excretion in asthmatic children receiving magnesium supplementation: randomized, placebo-controlled, double-blind study.
A randomized, double-blind, placebo-controlled prospective study investigated the effects of magnesium citrate supplementation in 89 children aged 4 to 16 years with mild to moderate, persistent bronchial asthma. Each subject received one 290 mg capsule of magnesium citrate/day or one 260 mg placebo capsule (glucose) daily during 12 weeks. Evaluations occurred at the end of 4-week intervals and blood samples of total, free and urinary Mg concentrations were determined at the beginning and end of the 12-week period. Bronchodilator use was significantly higher after 8 and 12 weeks in the placebo-treated group versus the Mg-treated group with moderate asthma. These results suggest a benefit of long-term Mg supplementation in mild to moderately asthmatic children. 23
Oral magnesium and vitamin C supplements in asthma: a parallel group randomized placebo-controlled trial.
A randomized, placebo-controlled, double-blind parallel group trial was conducted to determine whether vitamin C and magnesium (Mg) may be associated with a reduced risk of asthma. Three hundred patients aged 18 to 60 years were recruited from primary care practices and supplemented with either 1 gram/day of vitamin C and 450 mg/day of Mg chelate or placebo for 16 weeks. No beneficial effect was found from either vitamin C or Mg supplementation on any outcome measure of asthma control. 24
Magnesium deficiency is associated with periodontal disease.
An epidemiological, cross-sectional study investigated the potential association between magnesium and calcium levels and periodontal health. The study enrolled 4,290 subjects between the ages of 20 and 80 years. Serum concentrations of magnesium and calcium were assessed along with periodontal health. Higher magnesium and calcium concentrations were associated with reduced probing depth (p<0.001), less attachment loss (p=0.006), and a higher number of remaining teeth (p=0.005). Subjects taking magnesium containing drugs had lower attachment loss (p<0.01) and higher number of teeth remaining than matched controls. These results suggest that dietary magnesium supplementation may promote periodontal health. 27
A prospective, randomized, double-blind, placebo-controlled trial investigated the efficacy of magnesium supplementation to improve symptoms in idiopathic sudden sensorineural hearing loss. Subjects were randomly assigned to receive standard steroid therapy with magnesium or with a placebo. People who consumed daily magnesium supplements had significantly greater improvements compared to controls. Individual data analysis revealed that patients receiving magnesium also had greater hearing improvement than controls.29
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