An adult body contains approximately 250mg of Magnesium (Mg), with 50% to 60% stored in the bones and most of the rest in soft tissues [4]. Less than 1% of total Mg is found in the blood. Normal serum Mg concentrations range between 0.75-0.95mmol/L [1,5]. Hypomagnesemia is defined as a serum Mg level less than 0.75mmol/L [6]. Mg homeostasis is largely controlled by the kidneys, which typically excretes about 120mg Mg into the urine each day [2]. 

Signs of Mg deficiency include loss of appetite, nausea, vomiting, fatigue, migraine headaches, weakness and low levels of energy. As Mg deficiency worsens, numbness, tingling, muscle contractions and cramps, seizures, personality changes, abnormal heart rhythms, and coronary spasms can occur [1,2]. Low Mg is also associated with cardiovascular disease, high blood pressure, metabolic syndrome, diabetes, migraines, PMS, asthma, and hypothyroidism.

Why are so many people deficient in Magnesium?

The average intake of Magnesium (Mg) in a typical western diet is around 200-300mg per day, someone eating a Paleo diet will get closer to 350-400mg per day.  The recommended daily allowance (RDA) is between 300mg/day400mg depending on gender and age.  These recommendations are based on the minimum amount of Mg necessary to avoid serious health consequences; they are not set for the optimal levels required to perform over 300 biological processes in your body which are dependant on Mg.  You may have just enough Mg to avoid sickness, but it can be challenging to get enough Mg in the diet for many reasons:

  • Crap Diet - The increasing consumption of calorie-rich, micronutrient-poor foods (processed foods) -  We need to eat more dark green leafy vegetables (spinach, kale, collard greens, parsley, sprouts, etc...)

  • Mg absorption - many people eat food like oats, cereals, legume and wheat products and assume they get Mg from them.  However, these foods are high in phytates.  Humans are unable to digest phytates, and phytates bind to minerals, such as Mg and lower the bioavailability of all minerals.

  • Excessive excretion - after absorbing the Mg in the intestine the kidneys filter some of the Mg, typically around 5% is lost.  However, some diseases like diabetes, Crohn's disease, IBS, GERD, gluten-sensitive enteropathy (celiac disease), can increase the excretion rates.  Consuming alcohol can double the rate of Mg excretion in the kidneys.

  • Soil depletion - our soil has become progressively depleted in Mg.

Mg deficiency is widespread due to the increased consumption of processed foods, meats and dairy products, and a decrease in the intake of green chlorophyll-containing vegetables.  We need to start including more chlorophyll green in the diet.

TIP: If you do plan on having a big night drinking you should supplement with magnesium before bed and eat a large plate of spinach the very next day.

Why Do Athletes need more Magnesium?

Oxidative capacity depends on the availability of oxygen and the quality and quantity of mitochondria (energy factories) in the body.  The mitochondria are responsible for the creation of Adenosine Triphosphate (ATP) (Krebs cycle and Electron Transport Chain), the bodies currency of energy. You want your ATP production to exceed your ATP consumption in order to enhance your athletic performance and avoid muscle fatigue.

At the mitochondria level, you can increase oxidative capacity by:

  1. Increasing the total number of mitochondria

  2. Increasing the efficiency of the mitochondria

High-intensity exercise can results in an increase of mitochondria if supported by the diet.  In order to make new mitochondria, the body needs Mg as a co-factor.  If your Mg levels are low, you are going to have a difficult time benefiting for the high-intensity training and increasing your total mitochondria count.  If your goals are to improve your fitness levels, you need to be looking at your diet seriously.

Aerobic exercise causes the mitochondria to swell and break. Our bodies will quickly repair this damage, and after healing the mitochondria will have a greater volume.[12,16] The mitochondria will form a larger and stronger matrix, according to a January 2018 review in Antioxidants.[14] The researchers speculated that the stronger matrix lets your body effectively send essential molecules to the areas that most needing repair. It can speed up recovery.  To produce/repair mitochondria each of your existing mitochondria has to synthesise their genome and this depends on enzymes that require magnesium as a cofactor.[18,19]

The harder you work out, the more mitochondria you create if your body has the resources to do so. The repair and adaptation process depends on Mg availability [15].  You must, however, remain committed to the exercise program. Your mitochondrial levels will quickly decrease when you stop exercising. They return to normal levels within about a month [13, 17].

If you are a very physically active person, you should assess your Mg levels on a regular basis (1-2times per year) and increase your daily intake of Mg-rich foods (see table below for more info).

Assessing Magnesium Levels:

Evaluate Mg status is difficult because most Mg is stored inside cells or in bone [3]. The most commonly used and readily available method for assessing Mg status is the measurement of serum Mg concentration, even though serum levels have little correlation with total body Mg levels or concentrations in specific tissues [6]. Other methods for assessing Mg status include measuring Mg concentrations in erythrocytes, saliva, and urine; measuring ionised Mg concentrations in blood, plasma, or serum; and conducting an Mg-loading (or “tolerance”) test. No single method is considered satisfactory [7], but most investigative doctors will go with red blood cell (RBC) Mg scores.

It's also worth noting that acid-suppressing drugs and diuretics can lower Mg levels [20].

The Optimal Range?

The optimal range for Mg is 500-700mg per day from a combination of food and supplements.

Foods high in Magnesium

Magnesium is widely distributed in plant and animal foods and beverages. Green leafy vegetables, such as spinach. Nuts such as almonds and cashews, pumpkin seeds,  In general, foods containing dietary fibre provide magnesium. Magnesium is also added to some breakfast cereals and other fortified foods, but TSTM would not recommend these.

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The U.S. Department of Agriculture’s (USDA’s) Nutrient Database lists the nutrient content of many foods and provides comprehensive list of foods containing magnesium arranged by nutrient content and by food name.

Magnesium Supplements:

Absorption of magnesium from different kinds of magnesium supplements varies. Forms of magnesium that dissolve well in liquids are more completely absorbed in the gut than less soluble forms [2.11]. Small studies have found that magnesium in the aspartate, citrate, lactate, glycinate, and chloride forms is absorbed more thoroughly and is more bioavailable than magnesium oxide and magnesium sulfate [7-10]. 

One study found that very high doses of zinc from supplements (142 mg/day) can interfere with magnesium absorption and disrupt the magnesium balance in the body [11].  We do not recommend taking ZMA (Zinc + Magnesium) as a supplement because you have little control over the amount of each mineral in ZMA, its best to make them separately.

Research has shown taking Mg with high protein meals can increase Mg absorption rates. Vegetarians and vegans can often have troubles absorbing Mg due to a diet low in protein and high in phytates.

Mg supplements are great at lowering blood pressure, which means they can interfere with certain prescription drugs.  If you are taking medication for blood pressure, it is recommended that you speak with your doctor and keep a close eye on your blood pressure.

REFERENCES:

  1. Institute of Medicine (IOM). Food and Nutrition Board. Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D and Fluoride. Washington, DC, 1997

  2. Rude RK. Magnesium. In: Coates PM, Betz JM, Blackman MR, Cragg GM, Levine M, Moss J, White JD, eds. Encyclopedia of Dietary Supplements. 2nd ed. New York, NY: Informa Healthcare

  3. Rude RK. Magnesium. In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease. 11th ed. Baltimore, Mass: Lippincott Williams & Wilkins; 2012:159-75.

  4. Volpe SL. Magnesium. In: Erdman JW, Macdonald IA, Zeisel SH, eds. Present Knowledge in Nutrition. 10th ed. Ames, Iowa; John Wiley & Sons, 2012:459-74.

  5. Elin RJ. Assessment of magnesium status for diagnosis and therapy. Magnes Res 2010;23:1-5. [PubMed abstract]

  6. Gibson, RS. Principles of Nutritional Assessment, 2nd ed. New York, NY: Oxford University Press, 2005.

    Ranade VV, Somberg JC. Bioavailability and pharmacokinetics of magnesium after administration of magnesium salts to humans. Am J Ther 2001;8:345-57. [PubMed abstract]

  7. Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnes Res 2001;14:257-62. [PubMed abstract]

  8. Mühlbauer B, Schwenk M, Coram WM, Antonin KH, Etienne P, Bieck PR, Douglas FL. Magnesium-L-aspartate-HCl and magnesium-oxide: bioavailability in healthy volunteers. Eur J Clin Pharmacol 1991;40:437-8. [PubMed abstract]

  9. Lindberg JS, Zobitz MM, Poindexter JR, Pak CY. Magnesium bioavailability from magnesium citrate and magnesium oxide. J Am Coll Nutr 1990;9:48-55. [PubMed abstract]

  10. Walker AF, Marakis G, Christie S, Byng M. Mg citrate found more bioavailable than other Mg preparations in a randomized, double-blind study. Mag Res 2003;16:183-91. [PubMed abstract]

  11. Inhibitory effects of zinc on magnesium balance and magnesium absorption in man. Spencer H et al, 1994

  12. Effects of Exercise on Mitochondrial Content and Function in Aging Human Skeletal Muscle, Elizabeth V. Menshikova et al, 2006

  13. Principles of Exercise Prescription, and How They Influence Exercise-Induced Changes of Transcription Factors and Other Regulators of Mitochondrial Biogenesis. Granata et al, 2018

  14. Exercise and Mitochondrial Dynamics: Keeping in Shape with ROS and AMPK, Adam J Trewin et al, 2018

  15. Mitochondrial Mg2+ homeostasis decides cellular energy metabolism and vulnerability to stress, Ryu Yamanaka et al, 2016

  16. In vivo oxidative capacity varies with muscle and training status in young adults, Larsen RG et al, 2009

  17. Mitochondria express enhanced quality as well as quantity in association with aerobic fitness across recreationally active individuals up to elite athletes. Jacobs RA et al, 2013

  18. Crucial role for DNA ligase III in mitochondria but not in Xrcc1-dependent repair, Simsek D et al, 2011

  19. Kinetic mechanism of human DNA ligase I reveals magnesium-dependent changes in the rate-limiting step that compromise ligation efficiency, Taylor MR et al, 2011

  20. Relationship of diuretic therapy and serum magnesium levels among participants in the Multiple Risk Factor Intervention Trial. Kuller. L., et al. 1985