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Magnesium in Hypertension Prevention and Control

September 2004

By Jay S. Cohen, MD

LE Magazine September 2004
Magnesium in Hypertension Prevention and Control
By Jay S. Cohen, MD

The Magnesium Solution
Natural substances that lower blood pressure can differ significantly. First, there is a big difference between a nutrient and a supplement. Health care practitioners of all stripes often overlook this distinction. Taking an herb with pharmacological effects is not much different than taking a drug. If your blood pressure is rising because of nutritional deficiencies, it makes more sense to start with the very nutrients that are missing.

Which nutrients are the most important for maintaining a healthy blood pressure? Two that stand out are the metallic elements potassium and magnesium.

Most people and doctors know that adequate amounts of potassium are essential for maintaining healthy blood pressure. One of the main reasons that the DASH diet reduces blood pressure is that it provides a large daily supply of potassium. When doctors prescribe diuretics, they also recommend taking potassium, derived either from food sources (such as bananas or vegetables) or a prescription product.

Yet few doctors know that diuretics help flush magnesium as well as potassium from the body. The resulting magnesium deficiency hinders potassium use by the cells.8,9 “Magnesium deficiency keeps people from replenishing potassium,” says hypertension expert Chris Mende, MD. “So when patients are hospitalized and potassium levels are low, efforts to increase potassium often are hampered unless the magnesium deficiency is also treated.”

Nevertheless, magnesium’s im-portance in maintaining normal blood pressure and treating high blood pressure is not widely recognized. This is surprising because magnesium is one of the most intensively studied nutrients in the scientific literature. Thousands of studies of magnesium can be found in MEDLINE (, the National Institutes of Health’s vast collection of medical journal articles. Indeed, according to the National Institutes of Health:

“Evidence suggests that magnesium may play an important role in regulating blood pressure. Mag-nesium deficiency can cause meta-bolic changes that may contribute to heart attacks and strokes. There is also evidence that low body stores of magnesium increase the risk of abnormal heart rhythms, which may increase the risk of complications associated with a heart attack. Population surveys have associated higher blood levels of magnesium with lower risk of coronary heart disease.”10

Magnesium is one of the body’s most important minerals. It is required as a cofactor in hundreds of enzymatic processes within cells.11 Magnesium is a major factor in relaxing the smooth muscles within the blood vessels, thereby reducing peripheral vascular resistance and blood pressure.11-13 In addition, magnesium reduces nerve and muscle excitability, stabilizes cardiac conductivity, and influences neurochemical transmission.11,13,14 Magnesium also affects circulating levels of norepinephrine and the synthesis of serotonin and nitric oxide.11,14,15

Indeed, because of magnesium’s primary role in blood pressure regulation, for decades scientists have called magnesium “nature’s calcium channel blocker” because

magnesium directly offsets the constriction of blood vessels caused by calcium.11,14 Because drug companies cannot make money from a natural substance like magnesium, they have developed a whole group of drugs called calcium antagonists or calcium channel blockers to do what magnesium does. In 2000, doctors wrote more than 95 million prescriptions for calcium antagonists, including top sellers amlo-dipine (Norvasc®), nifedipine (Procardia®), diltiazem (Cardizem®, Tiazac®), and others at a total cost of more than $4.5 billion.16 These drugs are not only costly, but they can also cause side effects such as dizziness, palpitations, fatigue, tiredness, and swollen legs. Yet many doctors do not hesitate to prescribe these drugs because they were never taught about magnesium. While legions of pharmaceutical sales representatives bring stacks of studies and free samples of these drugs, no one pushes magnesium.17

Fortunately, a growing number of doctors are now learning about magnesium. Sherry Rogers, MD, a highly respected integrative medicine physician, has written extensively about magnesium’s benefits for disorders caused by abnormal muscle constriction: “In order for a muscle to contract, it needs calcium. In order to relax, it needs magnesium.”18 Hypertension is one of the conditions for which Dr. Rogers recommends supplementing with magnesium.

Magnesium in Treating High Blood Pressure
Numerous studies demonstrate magnesium’s importance in maintaining healthy blood pressure. Epidemiological studies, which survey the causes, prevalence, and distribution of disease in population groups, have found a clear relationship between magnesium in the diet and blood pressure: the more magnesium in the diet of a given population, the lower its blood pressure tends to be; conversely, the lower the amount of magnesium in the diet, the higher the blood pressure.19

For example, in studies of the natives of Greenland, the Bedouin peoples of the Middle East, the Bantu of southern Africa, and Australian aborigines, the incidence of high blood pressure and cardiac disease was low when the water they consumed or diets they ate were rich in magnesium. When these people moved to urban areas and adopted modern, magnesium-deficient diets, they developed hypertension and cardiac disease as often as their urban counterparts.19

In the US and other Western countries, the incidence of cardiovascular disease is significantly lower in people who live in areas with hard water containing a high concentration of magnesium.20 Vegetarians, who usually get a lot of magnesium in their diets, have a correspondingly lower incidence of hypertension, heart disease, and sudden cardiac death. Assessing the scientific data, Drs. Burton and Bella Altura, who have pioneered the study of magnesium and cardiovascular diseases, concluded in Scientific American: “At least 10 independent clinical studies show that patients with hypertension of diverse etiologies exhibit hypomagnesemia [low magnesium] in serum or tissues, or both.”19

Evidence-based studies have shown the same thing. A 1989 study published in the journal Hypertension found that taking 625 mg of magnesium daily produced significant reductions in blood pressure in 21 subjects.21 A study published in 1993 in the American Journal of Hypertension found that taking supplemental magnesium reduced average systolic blood pressure from 154 to 146 mm Hg and cut average diastolic blood pressure from 100 to 92 mm Hg. The authors commented: “For the first time in a double-blind, placebo-controlled study, we have demonstrated that oral magnesium results in a significant dose-dependent reduction of systolic and diastolic blood pressure.”22

A study published in the International Journal of Cardiology in 1996 found that taking 600 mg of magnesium daily reduced systolic blood pressure by an average of 7.6 mm Hg and diastolic pressure by an average of 3.8 mm Hg.23 In another double-blind, placebo-controlled study published in the British Journal of Nutrition in 1997, subjects who took 411-548 mg of magnesium daily experienced significant reductions in systolic and diastolic blood pressure.24

These and other studies25-27 create a compelling body of evidence for the use of magnesium in preventing and treating hypertension. In some studies, magnesium failed to reduce blood pressure significantly, though these studies typically were too brief in duration for the magnesium to reach maximum effect, or they used inadequate amounts or poorly absorbed types of magnesium. While some people obtained benefit from magnesium in these studies, not enough people did to achieve statistical significance.

Summarizing the studies, Mildred Seelig, MD, who has been studying magnesium for 60 years and has written numerous articles and books about this vital element, concluded: “The studies that employed the larger supplements of magnesium did in fact show that it has ability to lower high blood pressure.”28

Recognizing and Treating Magnesium Deficiencies
In 1900, the average American diet provided about 450 mg of magnesium a day. By 2000, the average diet provided only 200-225 mg of magnesium daily, well below the US RDA (recommended dietary allowance) of 320 mg for adult women and 420 mg for adult men (see Table 2). Thus, while most Americans in 1900 obtained adequate magnesium from their diets, today as many as 80% do not get enough.28,29 Similar deficiencies exist in all Western countries. A survey conducted in France in the mid-1990s found that 72% of men and 77% of women obtained less than the RDA of magnesium from their diet.30


The recommended dietary allowance (RDA) for magnesium is affected by age, gender, and other circumstances. Stress, for example, may increase the amount required. Some experts believe these allowances are too low. Amounts listed below are in mg per day.





















Modern food production contributes to the problem by using inadequate amounts of magnesium in plant fertilizers, as well as by employing accelerated growing techniques and refining methods that reduce magnesium content. Today’s dietary habits also exacerbate the problem. Soft drinks and other popular beverages contain large amounts of phosphates that interfere with magnesium absorption. Diets containing large amounts of fat, salt, coffee, or alcohol also interfere with magnesium absorption or cause magnesium loss. Calcium supplementation can reduce the absorption and increase the kidney excretion of magnesium and other vital minerals.

Despite all this, magnesium deficiencies are rarely recognized because there is no simple, widely available test for magnesium deficiency. Mainstream medical laboratories measure the total serum (blood) magnesium. This measurement is not very helpful; even if one is severely magnesium deficient, the body will maintain a normal blood level of magnesium by drawing magnesium from cells and bone. Thus, a normal serum magnesium level can mask even a major magnesium deficiency. Incidentally, the same is true for calcium, which is why osteoporosis is not diagnosed using a blood test but rather by measuring bone density.

Developing a reliable test that can accurately reflect magnesium levels in the tissues has been a challenge because less than 1% of the body’s total magnesium is contained in the blood, whereas about 55% resides in bone, 26% in muscle, and 18% in other tissues. Yet such measurement is possible today. Specialty laboratories can perform magnesium analyses on ionized blood, red blood cells, hair, and cells swabbed from the inner side of the cheek. These tests can be quite accurate and are frequently used by alternative doctors, though not by most mainstream doctors. If one of these tests became as standard as the others that doctors order, magnesium deficiencies would be widely recognized and properly treated.