A major difficulty in treating nutritional deficits stems from the fact that health consequences occur slowly over long periods of time. This means that there is little negative reinforcement for poor nutritional behaviours, as we tend to not associate our health today with the cumulative damage over the past number of years. If unhealthy nutrition immediately caused harm, our nutrition as a population would in all likelihood be much different than it is today. When it comes to magnesium specifically, its important biologic function is well established, and the sweeping rates of deficiency are very apparent. The focus must shift to the clinical identification of deficiency to prevent long-term health problems, and the application of nutrition to correct the deficiency.
While a thorough examination of the diet and health symptoms can usually point towards a magnesium deficiency, a true diagnosis requires objective measuring, in the form of a blood test. Interestingly, many people being tested are still slipping between the cracks. This is because the most commonly used testing methodology is poorly representative of true magnesium levels. In the blood, it is well established that nearly all magnesium (99%) is found inside cells, and only a small fraction is found outside cells (1%) (1). Most lab tests measure the serum, or fluid portion, of the blood for magnesium. You know a test will be a poor indicator when the sample being tested is already known to not contain what is being looked for in the first place. Thus, the first stage in identifying a magnesium deficiency should be looking inside cells, where it actually resides. People, especially the elderly, should be screened with an intra-erythrocyte test, rather than a serum test (2).
Healthy individuals should look no further than their daily nutritional intake to ensure they are getting a full complement of all nutritional components, including magnesium. Assuming there are no malabsorption issues, a whole foods (unprocessed) dietary intake that is largely composed of vegetables, fruits, beans/legumes, healthy fats, and lean protein should provide all the necessary vitamins and minerals. Adherence to this type of Mediterranean style eating pattern has been shown effective in the prevention of nutritional deficiencies (3). The best food sources for magnesium are nuts, seeds, legumes, whole grains, and leafy green vegetables (4), whereas the standard North American diet tends to be heavy in poor magnesium sources such as meat and processed foods.
People with absorption issues may require additional help in order to fill their magnesium stores. First, it is prudent to ensure vitamin D levels are adequate, as vitamin D increases magnesium absorption (5). If this fails to offset the deficiency, magnesium supplementation is likely indicated.
Magnesium supplements come in a variety of forms, with some being better than others. Elemental magnesium is unable to be absorbed through the gut, and therefore must be bound to a carrier molecule (6). Most widely available magnesium supplements are bound to an inorganic substance, amino acid, or Krebs cycle intermediate. First, inorganic bound magnesium (e.g. oxide and chloride), is the cheapest and most widely available magnesium supplement on the market. Unfortunately, with a bioavailability of only 4%, very little is absorbed, and this causes rapid diarrhoea (7), making it a more effective laxative than nutritional supplement. Second, amino acid bound magnesium (taurate, glycinate) has an upper to mid-range bioavailability, but is best tolerated, and therefore recommended for people with sensitive bowels. Finally, magnesium bound to Krebs cycle intermediates (citrate, fumarate, malate, and succinate) has the highest bioavailability of 90% (7), and has the advantage of feeding directly in to the Krebs cycle to produce ATP, which has been shown to improve energy and combat fatigue (8).
1. Rude R. Magnesium metabolism and deficiency. Endocrinology and Metabolism Clinics of North America. 1993; 22(2): p. 377-95.
2. Ulger Z, Ariogul S, Cankurtaran M, Halil M, Yavuz B, Orhan B, et al. Intar-erythrocyte magnesium levels and their clinical implications in geriatric outpatients. J Nutr Health Aging. 2010 December; 14(10): p. 810-4.
3. Cruz J. Dietary habits and nutritional status in adolescents over Europe. European Journal of Clinical Nutrition. 2000; 54: p. 29-35.
4. National Research Council. Dietary reference intakes for calcium, phosphorus, magnesium, vitamin d, and flouride Washington, DC: The National Academies Press; 1997.
5. Hodgkinson A, Marshall D, Nordin B. Vitamin D and magnesium absorption in man. Clin Sci. 1979; 57(1): p. 121-23.
6. Kayne L, Lee D. Intestinal magnesium absorption. Min Electrolyte Metab. 1993; 19: p. 210-17.
7. Lindber J, Zobitz M, Poindexter J, Pak C. Magnesium bioavailability from magnesium citrate and magnesium oxide. J Am Coll Nutr. 1990; 9(1): p. 48-55.
8. Abraham G. Management of fibromyalgia: rational for use of magnesium and malic acid. J Nutr Med. 1992; 3: p. 49-59.