Supplementation among athletes at any level has become a booming industry, with most attention and dollars focused on exotic and potentially harmful anabolic steroids. However, perhaps their attention should focus more on the basics of vitamins and minerals, essential elements that are commonly deficient even among apparently well-fed Americans. To be specific, we will examine magnesium deficiency and depletion, and the effects of supplementation on sports performance as well as overall health.
According to an online reference, the average mixed American diet supplies about 120 mg of magnesium per 1,000 calories (NationMaster.org, 2003-2005), yet according to revised dietary guidelines, that intake level can well put most of us into depletion territory.
Magnesium is the eighth most abundant element found within the human body; a 190-lb person possesses approximately 1 oz (23 gr) of magnesium (faqs.org). Yet at least ten percent of us are deficient in magnesium. Most of us do not recognize the signs of magnesium insufficiency until blood levels drop to severe levels; symptoms include personality changes, muscle spasms, tremors, numbness and tingling and in extreme instances, convulsions and delirium (NationMaster.com, 2003-2005). Magnesium is essential to both bone and muscle health, with the most important muscle in the body, the heart, especially vulnerable to signs of deficiency.
The body stores about half its magnesium inside the cells of tissues and organs. The other half is combined with calcium and phosphorus inside bones. A tiny amount, just 1 percent, of the body's magnesium circulates within the blood at a constant level (Lukaski et al, 2004).
The absorption of orally administered magnesium is unpredictable, but 45 percent is the usual estimate. Both magnesium hydroxide and magnesium oxide are capable of raising serum magnesium levels when administered orally (NationMaster.com, 2003-2005). Research on the effects of supplementation on sports performance or on other performance measures has been frustrating due to inconsistent results; but it is difficult to determine which form of magnesium was used in each study and whether one form is more easily absorbed than another. Different forms of magnesium also vary widely in actual magnesium content.
Magnesium oxide is 60 percent magnesium; magnesium carbonate is 45 percent magnesium; magnesium hydroxide is 42 percent; magnesium citrate is only 16 percent and magnesium lactate and magnesium chloride are 12 percent; magnesium sulfate is just 10 percent magnesium.
Magnesium Deficiency and Health Problems
What other functions and health conditions are affected by low magnesium levels?
Hypertension --An observational study with four years of follow-up, found that a lower risk of hypertension was associated with dietary patterns that provided more magnesium, potassium, and dietary fiber... Foods high in magnesium are frequently high in potassium and dietary fiber. This makes it difficult to evaluate the independent effect of magnesium on blood pressure.
Diabetes -- Magnesium plays an important role in carbohydrate metabolism. It may influence the release and activity of insulin, the hormone that helps control blood glucose (sugar) levels. Low blood levels of magnesium (hypomagnesemia) are frequently seen in individuals with type 2 diabetes. Hypomagnesemia may worsen insulin resistance, a condition that often precedes diabetes, or may be a consequence of insulin resistance.
Osteoporosis -- Bone health is supported by many factors, most notably calcium and vitamin D. However, some evidence suggests that magnesium deficiency may be an additional risk factor for postmenopausal osteoporosis. This may be due to the fact that magnesium deficiency alters calcium metabolism and the hormones that regulate calcium. Several human studies have suggested that magnesium supplementation may improve bone mineral density.
Cardiovascular Disease -- Some observational surveys have associated higher blood levels of magnesium with lower risk of coronary heart disease. In addition, some dietary surveys have suggested that a higher magnesium intake may reduce the risk of having a stroke. There is also evidence that low body stores of magnesium increase the risk of abnormal heart rhythms." (All four above quotes from National Institutes of Health page on Magnesium, 2005.)
Mitral Valve Prolapse -- A significant body of evidence [suggests] that magnesium deficiency is at least a symptom of MVP and that many of the symptoms of MVP syndrome are reduced or resolved by magnesium supplementation (Nelson, 2007).
(to be continued)
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