What’s Your Magnesium Level?
Serum levels correlate with grip strength,
leg-muscle power, and knee and ankle strength
ere’s a scenario for you guys: imagine that you’re here in Petaluma, California, home of the annual World’s Armwrestling Championship, where intimidation and brute force rule (all in good fun, of course). By dint of enormous effort and a little luck, you’ve made it to the finals, with only one match left—and your opponent is Arnold Schwarzenegger! And you beat him! (Daht’s fahntahstic, ja?) OK, maybe it doesn’t compute in this universe, but where’s the harm in doing a Walter Mitty now and then?
When we were “97-pound weaklings,” we boys pored over the Charles Atlas ads in popular magazines, dreaming of becoming musclemen who would put the sand-kicking beach bullies in their place while the girls swooned over us. Some of us even scraped together the money to send away for Atlas’s “Dynamic Tension” muscle-building program (now known as isometric exercises). Darned few of us, though—OK, technically only one of us—grew up to be Arnold Schwarzenegger. Still, we did the best we could, and we’ve gotten through life reasonably well with the muscles we developed.
It’s Never Too Late for Muscle Building
The question is, do we still have those muscles, and how strong are they? The answer will not please you. You probably already know it anyway: with aging comes a gradual loss of muscle mass and strength (this applies to the ladies as well as the men). It’s called sarcopenia, and it seems to be inevitable—although not necessarily to the degree that we commonly see in our society. As with every other aspect of our health, it all depends on how we have lived our lives thus far, in terms of diet, exercise, and other lifestyle choices—not to mention our genetic makeup and other aspects of pure luck.
We cannot, of course, turn the clock back and relive our lives the way Charles Atlas lived his (not that we’d want to, necessarily—he died of heart failure at age 80), but we can always do better from here on out, because it’s never too late to start building and strengthening muscles that may have fallen into disuse. You’ve probably seen or heard stories about folks in their seventies, eighties, or even nineties who took up exercise of one form or another (yoga, for example) and benefited greatly from it, in both physical and psychological terms. Sometimes the improvements, especially in those with arthritis, are truly amazing.
Connecting the Magnesium Dots
Exercising is vitally important for good health in general and physical fitness in particular, and it can make you feel great if you do it right. But other things are important too, such as diet—which, of course, includes the vitamins and minerals your body needs for optimal performance. It could be that the element magnesium plays an important role in muscle performance in the elderly. Here are half a dozen relevant facts to consider:
- Magnesium is intimately involved in cellular energy metabolism in the mitochondria, and abundant chemical energy is required for physical exertion.
- Magnesium depletion is associated with structural damage to muscle cells in athletes.
- Magnesium supplementation has been shown to increase muscle strength in young adults.
- Magnesium seems to be necessary for maintaining optimal muscle performance and exercise tolerance in postmenopausal women.
- Inadequate magnesium intake is common, especially in older persons.
- Sarcopenia is prevalent in older persons and is a strong, independent risk factor for disability and mortality.
Can we connect the dots? A team of researchers from Italy and the United States tried to do that by investigating whether there is a measurable association between serum magnesium levels and muscle performance in the elderly. That’s much easier said than done, however. Part of the challenge was to correct for, and thus rule out, numerous factors in the study population that might confound the results—factors such as age, sex, body mass index, calf-muscle area and density, several biological indexes (serum levels of calcium, albumin, hemoglobin, glucose, creatinine, and vitamin D), the presence of self-reported or medically diagnosed diseases, and levels of physical activity in the year before recruitment.
Magnesium Benefited Men and Women Equally
The researchers analyzed recorded data on 1138 men and women, average age 67, from an existing epidemiological study in Italy that was aimed at identifying risk factors for mobility-related disability in older adults, in whom poor muscle strength is a major cause of disability. The study was called InCHIANTI, short for Invecchiare in Chianti,which means Aging in Chianti (the region, not the wine—although aging in wine sounds like fun, doesn’t it?).
The men and women had been given four tests of muscular performance under controlled conditions: handgrip strength, knee-extension torque, maximum lower-extremity muscle power, and ankle-extension strength. The details of how these measurements were made need not concern us here. What matters is the results: in all four tests, the data showed a modest but measurable increase in muscle performance with increasing serum magnesium level. The relationships were statistically significant in all but the test for maximum lower-extremity muscle power, and the results were essentially the same for men and women.*
The More Magnesium, the Better
To see whether the relationships were being driven by the data from individuals whose serum magnesium levels were below or above the normal range, the researchers reanalyzed the data, using only those individuals who were within the normal range. The results were the same, indicating that the relationships hold across the full spectrum of serum magnesium levels: the more you have, the stronger you’re likely to be.
The researchers suggested three possible explanations for their results:
- Low magnesium levels may impair cellular energy production and cause structural and functional damage to proteins, which would limit muscle performance.
- Low magnesium levels may cause structural damage to muscle cells through increased oxidative stress and impaired calcium homeostasis (maintenance of calcium equilibrium).
- Low magnesium levels may induce an inflammatory status by enhancing the production of certain proinflammatory compounds. (A state of chronic, low-grade inflammation has been proposed as one of the main causes of frailty in the elderly.)
Eat Your Spinach!
It’s not possible to say, from the results of this study, whether supplementation with magnesium would be likely to improve any individual’s muscle performance. Based on a large body of existing knowledge, however, one can say that maintaining healthy magnesium levels is a very good idea. It’s important for helping to prevent hypertension, cardiovascular disease, type 2 diabetes, osteoporosis, migraines, and immune-system disorders.
Magnesium deficiencies in healthy adults with a good diet are rare because the element is so readily available in plant and animal foods—especially green leafy vegetables (the chlorophyll molecule contains a magnesium ion at its center). Probably the best vegetable source of magnesium is spinach (preferably without E. coli).* Bran and unrefined grains are also excellent sources of magnesium, as are legumes and nuts.
The primary risk for magnesium deficiency is age, because many older people simply don’t consume enough good, healthy food (this, of course, leads to other deficiencies as well). Also, however, there is an age-related tendency for magnesium absorption by the gut to decrease and for urinary excretion of magnesium to increase—a double whammy that increases the risk for deficiency. Severe deficiency can cause depressed calcium levels and disruptions of electrolyte metabolism, as well as muscle spasms, tremor, loss of appetite, nausea, vomiting, cardiac arrhythmias, and personality changes, among others.
Magnesium—as magnesium ions, Mg—is one of the four most important metals in human physiology, the other three being sodium, potassium, and calcium. Each of us has about 25 grams (0.9 ounce) of magnesium. Over 60% is found in the skeleton, about 27% in the muscles, 6–7% in other cells, and less than 1% in the blood and extracellular fluid.
Numerous inorganic and organic salts of magnesium are used in medicine and as home remedies. For example, milk of magnesia (a water suspension of magnesium hydroxide) is a mild base that acts as an antacid and laxative, and Epsom salts (hydrated magnesium sulfate) acts as a cathartic and anti-inflammatory agent. Other magnesium salts are used as analgesics, antipyretics, anticonvulsants, and lubricants. The form in which magnesium is usually provided as a nutritional supplement is the organic salt magnesium aspartate.
Magnesium’s role in the physiology of all living things is pervasive. In humans, it’s involved in over 300 essential metabolic reactions. Most prominent is its role in cellular respiration, or energy metabolism—it exists primarily as a complex with ATP (adenosine triphosphate), the body’s master energy molecule. Without magnesium, there would be no biochemical energy production, hence no life.
Magnesium is also required for synthesis of nucleic acids and the proteins they code for. It’s required as a cofactor for a number of enzymes involved in the synthesis of carbohydrates and lipids. Glutathione, the body’s premier antioxidant, could not be produced without it. It plays a structural role in bones, cell membranes, and chromosomes. It’s required for the active transport of other metal ions across cell membranes, thus affecting nerve transmission, muscle contraction, and heart rhythm. And it’s required for many cell-signaling functions (the conveyance of chemical messages within and between cells).
All four of the metals mentioned above, by the way, were discovered in 1807–1808 by the great English chemist Sir Humphry Davy. Elemental magnesium, which is not found in nature (it’s too reactive), was first produced in quantity in the mid-nineteenth century by the German chemist Robert Wilhelm Bunsen (of Bunsen burner fame), who showed how it could be burned to produce an extremely bright light; this proved invaluable to early photographers and provides much of the dazzle in fireworks.
The primary industrial application for magnesium is as an alloying agent to make tough, strong, aluminum-magnesium alloys that are used in beverage cans, automotive and aircraft components (if you’re the sporty type, perhaps your car has “mag wheels”), and consumer electronic devices, such as laptop computers, cell phones, and cameras.
Deficiency Bad — Supplementation Good
For adults aged 31 or older, the Food and Nutrition Board of the Institute of Medicine has set the Recommended Dietary Allowance (RDA) for magnesium at 420 mg/day for men and 320 mg/day for women (for adults aged 19–30, the figures are 400 and 310, respectively). In the United States, however, the average daily magnesium intake is about 320 mg for men and about 230 mg for women, or 24% and 28%, respectively, below the RDAs. A recent study showed that elderly American men and women consume only about 225 and 166 mg/day of magnesium, respectively, or 46% and 48% below the RDAs.
This deplorable situation is an indictment of our generally poor diet, which we seem to favor despite all the health experts’ admonitions about fruits and veggies. Fortunately, however, the problem is easily solved through supplementation. As always, amounts matter. Just as it’s potentially harmful to ingest too little magnesium, it’s also inadvisable to take too much, especially for those with impaired kidney function, which afflicts many elderly people. (If you have a kidney disorder, consult your physician before taking any magnesium supplement, including magnesium-based antacids or laxatives.)
Lisa Kyle Young
For all generally healthy adolescents and adults, the Tolerable Upper Intake Level (UL) for supplemental magnesium (all supplements combined), set by the Food and Nutrition Board of the Institute of Medicine, is a very conservative 350 mg/day. This represents the level of daily supplemental magnesium intake beyond which there is some risk of diarrhea or other gastrointestinal disturbances in some people; the risk increases with increasing intake and is easily reduced by scaling back if necessary. Highly excessive intakes (many grams or more per day) could, ironically, lead to muscle weakness, or worse.
Indulge Your Fantasies
OK, you can go back to Walter Mitty mode now, if you wish. Whether your fantasy is being brawnier than Arnold Schwarzenegger, brainier than Stephen Hawking, or something too private to discuss, there’s one thing you can fantasize about that probably will come true: being healthier as a result of taking judiciously selected nutritional supplements, such as magnesium.
- Dominguez LJ, Barbagallo M, Lauretani F, Bandinelli S, Bos A, Corsi AM, Simonsick EM, Ferrucci L. Magnesium and muscle performance in older persons: the InCHIANTI study. Am J Clin Nutr 2006;84:419-26.
- Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. National Academy Press, Washington DC, 1997.
- Ford ES, Mokdad AH. Dietary magnesium intake in a national sample of U.S. adults. J Nutr 2003;133:2879-82.