Magnesium: A Best-Kept Secret

By Emmett Hughes, DC, MS

Magnesium is the second most abundant intracellular positive ion, with potassium the most abundant. Sixty percent of the body’s magnesium is found in bone, 25 percent in muscle and the remainder in soft tissue and fluids, especially gastric juice. The majority of magnesium in muscle is found in the mitochondria, where it is thought to play a role in permeability of the outer membrane.1

Dietary intake of magnesium has gone down dramatically over the past 100 years. It is estimated that 68 to 80 percent of Americans are magnesium deficient.2-4 In places where water is harder, levels of magnesium are higher, and the incidence of coronary artery disease is lower. It appears, however, that 8 million deaths from sudden cardiac failure occurred in the United States between 1940 and 1994 because of magnesium deficiency.5-8

Testing and Absorption
Serum levels are a poor indicator of magnesium status. Heart muscle levels are almost 20 times higher than serum levels, so measuring white blood cell levels is a more sensitive test. The best test is ionic magnesium measurement or elemental X-ray analysis using a buccal smear. However, none of these methods are definitive.9,10

The rate of magnesium absorption is highly variable, estimated to be from as low as 24 percent to as high as 85 percent. It is mainly absorbed in the jejunum via facilitated diffusion and simple diffusion, with smaller amounts absorbed in the ileum and colon. Many factors regulate magnesium absorption, including vitamin D levels.11 As calcium levels go down, magnesium absorption increases. High intakes of calcium, protein, vitamin D and alcohol all increase magnesium requirements.

Health Functions
Magnesium performs many vital functions. It regulates the absorption of calcium and is involved in the structural integrity of bone. Without adequate magnesium, bones will be dense, but trabecular bone will have poor integrity. Northern European countries, where the calcium to magnesium ratio is 4:1, have the highest rates of osteoporosis, as well.12 

Magnesium has an effect of relaxing smooth muscle and is therefore useful in conditions such as hypertension, dysmenorrhea, constipation, asthma, angina, stroke and myocardial infarct. It decreases coagulation and acts as a calcium channel blocker, helping the heart to pump more effectively and regulating blood pressure.13-15 It is involved in the function of more than 300 enzymes, as well as in regulating muscle contractility and nerve impulses. Virtually all body systems also rely on magnesium for at least some of their metabolic functions.16-19

Dietary Requirements and Sources
Requirements of magnesium vary with age and certain conditions. The RDA for males is 350 mg/day; for females 280 mg/day, with pregnancy and lactation requiring 350 mg/day. Optimal intake is estimated to be between 600 and 800 mg/day. The best dietary sources of magnesium are whole grains, nuts and fruits. These include soy flour, buckwheat flour, tofu, figs, cashews, avocado, millet and brewer’s yeast.20

Magnesium Deficiency
Symptoms of magnesium deficiency can mimic many other disorders. These include fatigue, irritability, weakness, dysmenorrhea, muscle spasms or tightness, cardiomyopathy, anorexia, sugar cravings, hypertension, anxiety and poor nail growth.21-25 Deficiency can result from kidney disease and intake of diuretics and can cause depletion of potassium intracellularly and affect muscles and bones. Besides low intake, magnesium deficiency can be caused by malabsorption syndromes, hyperthyroidism, kwashiorkor, diabetes mellitus, alcoholism, pancreatitis, parathyroid disorders, high dietary phytic acid and diarrhea.26-28

The clinical use of magnesium can be applied to a variety of conditions. These include constipation, muscle cramping, torticollis, acute angina following a myocardial infarct or stroke, asthma, kidney stone prevention (especially when given with vitamin B6) and dysmenorrhea. Other candidates for magnesium supplementation are GI spasms or cramping, eclampsia, heart disease29,30 (especially cardiomyopathy), diabetes mellitus, nocturnal muscle cramps, mitral valve prolapse, toxemia of pregnancy, fibromyalgia, migraine headaches, lead toxicity, general fatigue, anxiety and irritability.

General dosing should be in the 600 to 800 mg range. However, for GI cramping, asthma, constipation and heart disease, it is recommended to take magnesium to bowel tolerance (until the bowel movements become “loose”). For nocturnal leg cramps, kidney stone prevention and eclampsia, magnesium should be paired with 50 to 100 mg of vitamin B6.

Toxicity of magnesium is fairly low, with diarrhea being the biggest problem. Reduce the dose until bowel movements return to normal to prevent other possible symptoms of magnesium toxicity, such as calcium deficiency, hypotension, depletion of potassium and respiratory depression.31 Once a maintenance dose is established, calcium should be taken along with magnesium, in a 2:1 ratio.

For DCs treating acute muscle spasms, magnesium supplementation is a critical and often overlooked intervention. With the addition of magnesium supplementation to treatment protocols for myospasm, improved outcomes can be anticipated. 

Emmett J. Hughes, DC, MS, is associate professor of basic science at the University of Bridgeport College of Chiropractic. Since 1997, he has taught physiology, microscopic anatomy and physiology, clinical nutrition and soft-tissue technique. Dr. Hughes also maintains a private practice in Huntington, N.Y.   

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Published in the June 2010 issue of ACA News.