Magnificent Magnesium

Calcium is the mineral that has always had the most media attention, as well as overwhelming approval from the medical profession as a supplement that women should be taking. That in itself may be enough to arouse suspicion. As you might suspect, there are other more important minerals to consider for optimal health. For example, despite a great deal of published medical and biochemical research, there is little, if any, attention paid to calcium’s neglected cousin, magnesium, and most certainly no medical pronouncements that anyone should be supplementing this mineral in any serious way. Its under-utilization in clinical medicine is nothing short of scandalous, especially regarding its use as a life-saving cardiovascular tonic.

Magnesium appears by many names. Below is a list of how you might see it in health food stores and pharmacies: Chelated Magnesium, Dolomite, Epsom Salts, Magnesia, Magnesium Aspartate, Magnesium Carbonate, Magnesium Chloride, Magnesium Citrate, Magnesium Disuccinate Hydrate, Magnesium Gluconate, Magnesium Glycerophosphate, Magnesium Glycinate, Magnesium Hydroxide, Magnesium Lactate, Magnesium Malate, Magnesium Murakab, Magnesium Orotate, Magnesium Oxide, Magnesium Phosphate, Magnesium Sulfate, Magnesium Trisilicate, Milk of Magnesia.

Magnesium Facts and Figures

Magnesium is the second most plentiful cation (positive ion) in the intracellular (inside cells) fluid and the most plentiful cation in the body involved with more than 300 enzyme systems; it plays an essential role in more than 300 cellular reactions; the body contains about 25 grams of magnesium, divided equally between the skeleton and soft tissue; extracellular (outside cells) magnesium makes up only 1% of total body magnesium absorbed throughout the gastrointestinal tract, although whether maximal absorption occurs in the duodenum or colon is unclear; about one third of dietary magnesium is absorbed, with efficiency of absorption depending on magnesium stores in the body, among other factors. Average absorption of supplements is 38%, but varies from 65% in people with low magnesium stores to 11% with high magnesium stores. It is important for normal bone structure required for the formation of cyclic AMP (cAMP) and is involved in ion movements across cell membranes. It requires both parathyroid hormone and vitamin D for absorption. Magnesium is excreted mainly through the kidneys.

Sources and Bioavailability of Magnesium

Magnesium is well absorbed from food sources such as legumes, whole grains, vegetables (especially broccoli, squash, and green leafy vegetables), seeds, and nuts (especially almonds). Magnesium is the central element of chlorophyll, the substance that gives plants their green colour. Hence, if it’s green, consider the food as a potentially good magnesium source.

Water with a high mineral content, or “hard” water, is also a source of magnesium. So-called “soft water” (e.g. distilled or reverse osmosis water) is not only void of magnesium but may actually promote its loss from the body.

Absorption of magnesium from supplements (i.e. bioavailability) varies. Magnesium chloride, magnesium lactate and magnesium aspartate appear to be most bioavailable. Magnesium oxide and magnesium sulfate have bioavailability only of about 4%. Enteric coating of some products may reduce the absorption of magnesium.

Magnesium Deficiency Effects

Magnesium deficiency is not uncommon in North America, especially among African Americans and the elderly. Low intake and impaired absorption of magnesium are associated with osteoporosis, hypertension, atherosclerotic vascular disease, cardiomyopathy, diabetes, and stroke.

Serum magnesium levels are depressed only in cases of severe magnesium deficiency and it poorly correlates with body magnesium. The body preserves serum magnesium at the expense of magnesium in cells and bone, so serum levels may appear normal in magnesium deficiency. Red cell and urine magnesium levels are also poor indicators of body magnesium. The intravenous magnesium loading test is considered to be a more reliable test to measure magnesium status but the test is cumbersome and is known for poor patient compliance.

Free ionic magnesium levels have been shown to vary with many disorders such as cardiac disease, stroke, diabetes, and migraines but measurement of ionized magnesium may not be readily available in labs outside the research setting.

Since magnesium is an anti-spasmodic or relaxant, one expects and sees symptoms of severe magnesium deficiency to include convulsions, confusion, muscle weakness, abnormal muscle movements such as spasms, tremors, myoclonus, and tetany as well as arrhythmias including ventricular tachycardia, fibrillation, and something called torsades de pointes.

Magnesium is often referred to as nature’s calcium channel blocker. When intracellular levels of magnesium are low, this causes an increase in intracellular calcium. In addition to contributing to insulin resistance, higher intracellular calcium levels enhance calcium-mediated vasoconstriction, and inhibit cardiac and smooth muscle relaxation. The increased vascular tone can cause increased blood pressure. The pharmaceutical industry makes use of calcium channel blocking drugs to reverse this.  Practitioners in the natural health care industry use magnesium to accomplish this with fewer side effects.

Low serum magnesium is related to low-grade chronic inflammation. Magnesium deficiency is associated with elevated serum concentrations of tumour necrosis factor-alpha and C-reactive protein (CRP). People with high dietary magnesium intake have lower levels of CRP, which may reduce cardiovascular disease risk. Consuming less that the recommended dietary allowance (RDA) for magnesium is associated with a 1.48 to 1.75 times higher risk of having an elevated CRP.

Health Enhancing Uses of Magnesium

The following list includes many well documented uses of magnesium in health promotion: to correct magnesium deficiency; laxative effects (constipation and to prepare bowel for colonoscopy or surgery); asthma; allergic rhinitis; cancer-associated neuropathic pain; cardiovascular disease: angina, arrhythmias, hypertension, coronary heart disease and hyperlipidemia, low high-density lipoprotein (HDL) levels, mitral valve prolapse, vasospastic angina, myocardial infarction; multiple sclerosis; as an antacid for symptoms of gastric hyperacidity; attention deficit-hyperactivity disorder (ADHD); anxiety.

Magnesium is also known to prevent or alleviate the following conditions: improves chronic fatigue syndrome (CFS) – in people with low red blood cell magnesium, there is some evidence that weekly intramuscular injections of 1 gram magnesium sulfate improves CFS symptoms; lyme disease; fibromyalgia; pregnancy-induced leg cramps; diabetes, insulin resistance and metabolic syndrome; kidney stones (magnesium can prevent the recurrence of especially calcium oxalate stones); migraine headaches and cluster headaches; neuroprotective agent in patients diagnosed with acute stroke; osteoporosis; post-hysterectomy pain; premenstrual syndrome; altitude sickness; urinary incontinence; erythromelalgia; restless leg syndrome; preventing hearing loss; paranoid schizophrenia treatment because levels appear to be lower in acute attacks of paranoid schizophrenia; by athletes to increase energy and endurance; topically, used for treating infected skin ulcers, boils, and carbuncles, and for speeding wound healing; stroke risk reduction in men; topically as a cold compress in the treatment of erysipelas and as a hot compress for deep-seated skin infections.

Intravenously (IV) or intramuscularly (IM), magnesium is used for acute hypomagnesemia occurring in conditions such as pancreatitis, malabsorption disorders, and cirrhosis, and for treating pre-eclampsia and eclampsia (toxemia of pregnancy); considered the agent of choice for pre-eclampsia and eclampsia; as an additive to total parenteral nutrition (TPN); controlling seizures (IV or IM) associated with epilepsy, glomerulonephritis, or hypothyroidism when low serum magnesium levels are present; IV or IM in the treatment of atrial and ventricular arrhythmias, for preventing arrhythmias after myocardial infarction and for cardiac arrest; IV for treating acute exacerbations of asthma and chronic obstructive pulmonary disease (COPD), for migraine headaches, neuropathic pain and postoperative pain, as an osmotic agent for cerebral edema, and for tetanus; both oral and IV forms reduce the need for numerous prescription drugs.

Magnesium Safety Issues

Used orally, magnesium is safe when used in doses below the tolerable upper intake level (UL) of 350 mg per day. Doses greater than that frequently cause gastrointestinal irritation, nausea, vomiting, loose stools and diarrhea. Prolonged diarrhea caused by excessive magnesium intake can even cause worsening magnesium deficiency.

Doses of 5000 mg daily have been used IV and IM without significant side effects. Intravenously, rapid infusion of magnesium can cause a flushing sensation, local pain and irritation, dizziness, bradycardia (a very slow heart rate), and low blood pressure. In children, magnesium is safe when used in doses below the tolerable upper intake level (UL) of 65 mg per day for children 1 to 3 years, 110 mg per day for children 4 to 8 years, and 350 mg per day for children older than 8 years. Higher doses can cause diarrhea and symptomatic hypermagnesemia (high blood magnesium) including hypotension, nausea, vomiting, and bradycardia (slow heart rate). Some research suggests intravenous magnesium at higher doses in pregnant women can increase fetal mortality and adversely affect neurological development.

Although extremely rare, death is possible from excess magnesium supplementation. There are two reports of fatal hypermagnesemia. One report involved a 28 month-old child treated with 800 mg of oral magnesium oxide per day for constipation, then given 2400 mg magnesium oxide for several days before hospital admission. Another report involved a patient who gargled with Epsom salts (almost 100% magnesium sulfate) over several weeks. The patient used an entire box two days prior to hospital admission. Just a reminder here that deaths can occur with drinking too much spring water too. Virtually any natural or synthetic substance can be toxic to some individual at some dose.

Supplement Interactions

Boron supplements can reduce urinary excretion of magnesium and increase serum levels in women. This may be one of the reasons why boron is effective supplementation for osteoporosis.

Calcium supplements, when unbalanced by magnesium, can decrease the absorption of dietary magnesium, but only at very high doses (2600 mg per day). The advice here, especially for those at high risk for magnesium deficiency is to take calcium supplements at bedtime, instead of with meals, to avoid inhibiting dietary magnesium absorption. This may help explain the finding a few months ago showing that people who used high doses of calcium supplements tended to have higher rates of heart disease. Magnesium, on the other hand, does not seem to affect calcium absorption.

If you use high doses of zinc, you might also need a magnesium supplement. Supplementation with high doses of zinc, 142 mg/day, decreases magnesium absorption and magnesium balance in healthy adult males. Moderately high dietary zinc intake (53 mg per day) seems to increase magnesium excretion without affecting copper metabolism in postmenopausal women. Zinc may compete with magnesium for ion exchange transport in the intestine but research on the clinical importance of these observations is needed.

Alcohol abuse increases the risk for magnesium deficiency because alcohol impairs the ability of the kidney to conserve magnesium.

Magnesium / Drug Interactions

Neuromuscular weakness and even paralysis can occur if magnesium and aminoglycoside antibiotics are taken concurrently. The aminoglycosides include amikacin (Amikin), gentamicin (Garamycin), kanamycin (Kantrex), streptomycin, and tobramycin (Nebcin).

Magnesium can form insoluble complexes with quinolone antibiotics (ciprofloxacin (Cipro), levofloxacin (Levaquin), ofloxacin (Floxin), moxifloxacin (Avelox), gatifloxacin (Tequin), and others) and decrease their absorption. It is best to take these drugs at least 2 hours before, or 4 to 6 hours after, magnesium supplements.

Magnesium can also form insoluble complexes with tetracyclines and decrease their absorption and antibacterial activity). It’s therefore best to take these drugs at least 2 hours before, or 4 to 6 hours after, magnesium supplements. Tetracyclines include demeclocycline (Declomycin), doxycycline (Vibramycin), minocycline (Minocin), and tetracycline (Achromycin, Sumycin).

Magnesium can decrease bisphosphonate (e.g. Fosamax, Actonel, Didronel) absorption. If one separates doses of magnesium and these drugs by at least 2 hours, no adverse reaction can occur.

Magnesium inhibits calcium entry into smooth muscle cells and may therefore have additive effects with calcium channel blockers like amlodipine (Norvasc). Severe hypotension and neuromuscular blockades can occur when nifedipine (Adalat) another calcium channel blockers used with intravenous magnesium.  Does this necessitate removing magnesium from the market? How about removing calcium channel blockers from the market? Just be careful to avoid the two taken together.

Theoretically, increased magnesium levels could result from concomitant use of potassium-sparing diuretics and magnesium supplements. The potassium-sparing diuretics include amiloride (Midamor), triamterene (Dyrenium), and spironolactone (Aldactone).

Loop diuretics (furosemide (Lasix), bumetanide (Bumex), ethacrynic acid (Edecrin), and torsemide (Demadex)) and, to a lesser extent, thiazide diuretics (hydrochlorothiazide (Esidrix, HydroDiuril), chlorothiazide (Diuril)), interfere with magnesium reabsorption in the kidneys, which increases urinary losses and reduces serum magnesium levels.

Estrogen therapy including the use of oral contraceptives lowers serum magnesium levels and can cause hypomagnesemia, especially in people with low dietary magnesium intake or other factors contributing to magnesium loss.


Magnesium is just one of numerous trace minerals that are highly important both for disease prevention and treating existing illness as far ranging as asthma, osteoporosis, migraine headaches, coronary artery disease and diabetes. Before reaching for that anti-spasmodic, analgesic or anti-inflammatory drug, you might be better off considering healthy doses of magnesium. The optimal doses depend on the health situation, the current magnesium level and other biochemical individuality factors. If you are not sure what to do, consult a natural health care practitioner.


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