Based on the poor quality of what comes out of the municipal tap, health-conscious people often rely on bottled or home-filtered water for their drinking needs. While most filtered and bottled waters are free of cancer-causing contaminants, they provide little or no magnesium. Even most tap water is devoid of this critical mineral.
The implications of this widespread magnesium deficiency are frightening, in as much as communities with low magnesium content in drinking water show increased rates of sudden death.
Magnesium plays hundreds of crucial roles in the body, including suppressing unstable heart rhythms, controlling blood pressure, maintaining insulin sensitivity, and regulating over 300 enzymes. Attaining optimal magnesium levels is an absolute requirement for good health.
In this article, we examine magnesium’s importance to human health, how changes in the way we obtain our drinking water have contributed to widespread magnesium deficiencies, and strategies you can use to optimize your magnesium intake through dietary sources, better bottled waters, and nutritional supplementation.
Magnesium: Lost in the Filter
Our human ancestors evolved in a world in which healthy drinking water came directly from streams, rivers, and lakes, rich in mineral content. The human body became reliant on obtaining a considerable proportion of its daily mineral needs from natural water sources.
Fast-forward to the twenty-first century. We obtain drinking water from a spigot or a plastic bottle. Pesticides and other chemicals seeping into the water supply have made everyone suspicious of water quality. As a result, municipal water-purification facilities have intensified their efforts to remove contaminants like lead, pesticide residues, and nitrates from drinking water. Unfortunately, these modern water-treatment methods also deplete drinking water of desirable minerals like calcium and magnesium.
Exacerbating this problem is that many Americans, distrustful of the purity and safety of municipally treated water, have added home water filters and purifiers that efficiently extract any remaining minerals from the water, thus converting “hard” into “soft” water. In fact, the manufacturers of these devices boast of their power to yield water free of “contaminants”—including minerals like magnesium. Thus, the magnesium content of the water that passes through most commercial filters is zero.1
The present-day enthusiasm for bottled water has further compounded the problem. Americans consumed nearly 8 billion gallons of bottled water last year. The mineral content of these products varies widely. While some mineral waters, particularly those from Europe, contain a moderate amount of magnesium, other brands of bottled water contain little or none.2
The upshot of all this is that we cannot rely on drinking water to provide adequate magnesium. The recommended dietary allowance (RDA) for magnesium—that is, the amount required to prevent severe deficiency—is 420 mg a day for men and 320 mg a day for women. In cities with the highest magnesium water content, only 30% of the RDA can be obtained by drinking two liters of tap water a day.4 In most cities, only a meager 10-20% of the daily requirement can be obtained. That leaves 70–90% of the daily magnesium requirement that must be obtained from other sources. Since many people’s diets are also low in magnesium, the average American ingests substantially less magnesium than the RDA.3
The problem may be even worse than it appears. Many authorities believe that higher levels of magnesium are needed to avoid serious illnesses such as heart disease.4 Others argue that “normal” magnesium blood levels reported by laboratories, originally derived from populations symptomatic with magnesium deficiency, are also too low and that higher blood levels are necessary for optimal health.5
Low Magnesium Tied to Risk of Sudden Death
“Results from the early epidemiological studies suggest that sudden-death rates in soft-water areas are at least 10% greater than sudden-death rates in hard-water areas.
If magnesium supplementation causes even a modest decrease in sudden-death rates, a substantial number of lives might be saved.” 7
—Mark J. Eisenberg, MD, MPH - McGill University
Magnesium deficiency may have potentially dire consequences. Critically ill patients, who often have very low magnesium levels, suffer the risk of seizures, life-endangering heart rhythms, and fatal heart attack.8
Magnesium has a stabilizing effect on cell membranes, particularly in heart muscle. A healthy heart generates stable, predictable electrical impulses. Lack of magnesium permits unstable electrical impulses in the heart to emerge, generating abnormal heart rhythms.9,10 In fact, much magnesium research over the years has focused on its administration during heart attack to reduce death from fatal heart rhythms.11
Magnesium blood levels are routinely monitored in hospitalized patients, particularly those who are receiving diuretic medications. It is well known in hospitals that if magnesium blood levels drop too low, abnormal heart rhythms can suddenly develop, necessitating intravenous replenishment of magnesium.9 Dangerous rhythms of the heart’s ventricles, in particular, can occur. People suffering from congestive heart failure are especially susceptible to dangerous heart rhythms when magnesium is low.
Scientists have observed that people in areas with higher levels of magnesium in their drinking water exhibit rates of sudden cardiac death that are three to four times lower than those of people living in municipalities with the lowest magnesium levels in drinking water.7,12,13 This has drawn the attention of national and international public health officials. For example, a recent World Health Organization (WHO) report on the quality of drinking water cited 80 studies that have examined the relationship between cardiovascular death and water “hardness” (measured principally by magnesium and calcium content). The WHO concluded that the magnesium content of water is indeed a cardiovascular risk factor and that supplementing drinking water with magnesium should be a priority, much as fluoride became one.14 To date, however, no action has been taken.
The Many Perils of Magnesium Deficiency
The older you are, the more likely magnesium depletion is to develop,15 with substantial deficiency common by the age of 50. If you have any condition that causes frequent loose stools, magnesium depletion may be severe. This is also true in celiac disease (gluten enteropathy) and in those who have had bowel resection surgery. Some evidence suggests vitamin D deficiency may exacerbate magnesium deficiency.16
Unfortunately, blood magnesium levels are a poor barometer of true body (intracellular) magnesium levels. Only 1% of the body’s magnesium is in the blood; the remaining 99% is stored in various body tissues, particularly bone and muscle.16 If blood magnesium is low, cellular magnesium levels are indeed low—very low. If blood magnesium is normal, cellular or tissue levels of magnesium may still be low. Unfortunately, tissue magnesium levels are not easy to ascertain in living, breathing humans. In one study, only 8% of coronary patients had low blood magnesium, while tissue levels were reduced in 53%.10 In other words, normal blood magnesium levels do not rule out the possibility of a magnesium deficiency.
Short of performing a biopsy to measure tissue magnesium levels, potential magnesium deficiency may manifest as:
- Cardiac arrhythmias. Low magnesium levels can trigger abnormal heart rhythms. If you have been diagnosed with a cardiac arrhythmia, it is a good idea to ask your doctor about your magnesium level.16
- Low potassium. Low magnesium commonly accompanies low potassium.10 Potassium is an electrolyte that is depleted by the use of diuretics and is commonly deficient in many conditions (such as excessive alcohol use, hypertension, and diarrhea). Like magnesium, deficient potassium may not be easily remedied through diet.
- Muscle cramps. Magnesium regulates muscle contraction. Leg cramps, or a “charley horse”—painful, vise-like cramps in calves or other muscles—are a common symptom of magnesium deficiency. (Note that leg cramps that occur with physical activity, such as walking, are usually due to atherosclerotic blockages in the leg or abdominal arteries, not low magnesium.)17,18
- Migraine headaches. Reflecting magnesium’s role in regulating blood vessel tone, low magnesium can trigger vascular spasm in the membranes that cover the brain and spinal cord.19
- Metabolic syndrome. The risk of developing metabolic syndrome—the cluster of metabolic abnormalities that includes low high-density lipoprotein (HDL), high triglycerides, high blood pressure, increased blood sugar, and excessive abdominal fat—is clearly linked with lower magnesium levels. Magnesium plays a fundamental role in regulating cellular responses to insulin.20
The absence of any of these telltale signs does not necessarily mean that tissue levels of magnesium are normal. Then how can one know whether magnesium levels are deficient? There is no easy, available method to gauge body magnesium. In all practicality, because of magnesium’s crucial role in health, its widespread deficiency in Americans, and the growing depletion of magnesium in water, supplementing with magnesium may be the best way to ensure adequate total body magnesium levels.