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Magnesium, in the minds of many athletic health and performance experts, is the single most important mineral in sports nutrition. Magnesium is an essential nutrient, which means the body can't produce it and it therefore must be supplied by adequate intake in the diet.  This mineral is required by virtually all of the body's cells. It is an important cofactor to enzymes and drives over 300 biochemical processes. Magnesium also plays a vital role in the chemical process by which adenosine triphosphate (ATP) gets formed in the mitochondria of each cell. ATP is in greatest quantities in muscle cells and is the body's chief form of energy storage. It is also directly involved in red blood cell formation, muscle contraction and relaxation, glucose utilization, energy metabolism, blood pressure regulation, hormonal interactions, immune function, inflammatory response, nerve activity, protein and fat synthesis, bone health, the ionic balance of cells, and the production of RNA and DNA. Magnesium is a mineral electrolyte and aids electrical conduction in the heart. It has also been found to possess antioxidant properties, reducing oxidative damage in the body.  It is no surprise then, that this mineral, in ample supply, is an absolute must for optimal athletic performance as well as the sustenance of basic human health and function.


Vigorous exercise requires the breakdown of ATP for immediate energy needs.  The more rigorous and intense the activity, the greater the amount of ATP that gets used up and needs to be quickly replaced.  This rapid energy production is impeded if magnesium is in short supply and athletic output capabilities suffer. Symptoms of reduced power, cramps, muscle twitches, fatigue, and lethargy can all result. Long term deficiency of magnesium can result in decreased bone density tending toward osteoporosis, insulin resistance, anemia, metabolic syndrome, depression, high blood pressure and irregular heart beat.  Because of magnesium's wide breadth of roles in bodily functions, an athlete with deficiency can have a varied and complex presentation of symptoms in addition to declining or hampered performance.


Unfortunately, though magnesium is of vital importance to so many biochemical processes, it is estimated that over 70 percent of the general populous doesn't consume sufficient amounts. The average diet contains less than a third of daily requirements.  Dietary needs are significantly greater for athletes than more sedentary individuals. Athletes lose magnesium through sweat and this effect is greatest in hot, humid climates. Strenuous exercise also increases magnesium excretion in urine and this loss is much greater than with sweat. Performance can suffer and symptoms occur with even slight deficiency.  Muscle weakness and cramping, muscle twitching, increased nervousness and irritability, confusion, migraines, asthma and wheezing can all occur when magnesium levels are slightly down. At the extreme, crashing levels of magnesium during prolonged intense exercise have been implicated in the deaths of some long distance runners who have died suddenly while running from associated heart arrhythmias.  

Research has shown magnesium supplementation to improve exercise stamina and to reduce lactate buildup in muscle. It has also been shown to diminish fatigue experienced during strenuous exercise.  Low magnesium intake has been shown to reduce metabolic efficiency by increasing oxygen consumption and heart rate required for work output. Magnesium is necessary for muscles to fully relax following contraction.  Proper magnesium levels help optimize performance and contribute to faster recovery from exercise and injuries.


Magnesium is a macro-mineral which means the body requires large quantities of it.  The recommended daily allowance (RDA) of magnesium intake for 9-13 year olds is only 240mg. For fourteen years and older the numbers vary by age and sex but are 400-420mg for adult males and 310-360mg for females. Some research has shown the athletic benefit of magnesium intake to max out at the RDA level. The RunTheLabs recommended intake for endurance athletes is to consume much magnesium rich foods daily.  Many experts feel the RDAs for magnesium are too low and recommend up to 500 to 800mg per day depending upon body mass, activity levels, and any symptoms of insufficiency at current intake levels. These amounts would be very difficult to obtain from food sources alone and most athletes will want to supplement. We recommend supplementing between 200-400 mg per day.  . Those with known or suspected kidney impairments should supplement only under the supervision of a physician as they are at higher risk for adverse affects of any type of supplementation. As older individuals are more prone to kidney impairment, those over 50 should restrict supplemental magnesium to no more than the RDA per day unless their kidney function has been cleared by their physician.  


Magnesium should be taken in multiple doses throughout the day to avoid exceeding bowel tolerance.  At too high a dose for any individual, magnesium can cause loose stools. The Food and Nutrition Board of the Institute of Medicine set a tolerable upper limit of 350mg per day which they suggest is the maximum dose most individuals can handle without risk of diarrhea or gastrointestinal(GI) symptoms.  While the GI reaction can be a brief and unpleasant side affect of supplementation, it can also be useful. Many clinicians who work with nutritional supplementation use bowel tolerance to determine individual needs and tolerances for magnesium. It is often recommended to start with a lower dose of say 50-100mg of magnesium two times per day.  If this level isn't tolerated, lower the dose, but if after a week all is fine, add 50-100mg to each dose. Continue this process, week by week, until bowel tolerance or a satisfactory intake of magnesium is reached. We recommend this supplemental level to be between 200-400 depending on body mass but many sources support the supplementation of magnesium up to 5mg per pound of body weight. The supplemental amount, again, would also be affected by activity levels and dietary magnesium content and the calculation to determine supplemental need discussed above.  


Almost everybody, not already doing so, will benefit from increasing their daily magnesium intake. Every athlete should strive to eat more foods rich in magnesium such as beans, nuts, seeds, fruits and vegetables. The USDA publishes nutrient content of foods in their National Nutrient Database for Standard Reference Release 28.  This can be a valuable resource for athletes looking to understand more about the nutrient content of their diets. Review some of the magnesium content of foods here:

As you will see, magnesium content is highest in many nuts and seeds, spices such as cilantro, basil, dill, fennel, brown rice, cereals, oily fish such as mackerel, dark leafy greens, and moderate in many fruits and other vegetables.



Magnesium absorption is compromised by high levels of alcohol consumption, low calorie diets, and high sugar and refined carbohydrate intake.  It can also be impaired by gastrointestinal disorders, by conditions such as diabetes, and by certain over the counter and prescription medications.  Hypochlorhydria and achlorhydria,  common conditions involving impaired ability to produce stomach acid, impedes digestion and nutrient absorption including magnesium.  Over three dozen prescription medications interfere with magnesium absorption and retention. These include, but are not limited to acid blocking medications and antacids, many blood pressure meds, antiviral agents, corticosteroids, central nervous system stimulants, hormone replacement therapy, oral contraceptives, some antibiotics and certain immunosuppressants. So if you are on medication, research your medicines effects on magnesium levels and incorporate this information in your nutritional strategy to optimize your magnesium intake.  


Magnesium can interfere or interact with some medications and caution should be applied.  Issues with magnesium and medications such as digoxin(heart med), nitrofurantoin, quinolone, tetracycline, and penicillamine antibiotics, bisphonphonates (osteoporosis meds), some anti-malarial drugs, and oral anticoagulants are examples.  Anyone on these or other medications known to interact negatively with magnesium should consult their physicians with regards to supplementation.



Types of Magnesium Supplementation:


Magnesium, like most supplemental minerals, is available in a variety of forms.   Magnesium salts are formed by the combination of magnesium and another molecule to form a salt that is soluble in water.  They are referred to in chemistry terms as inorganic magnesium. Of them, magnesium chloride, the form of magnesium found in sea water, is thought to be the most bioavailable. It is easily absorbed and the chloride can be beneficial for kidney function and metabolism.   Another salt, magnesium oxide, is common in supplements due to low cost but is poorly absorbed and it's use for supplementation is not recommended. As well, magnesium sulfate or Epsom salt, while an effective laxative, is not a safe or suitable magnesium supplement.


Magnesium can also be supplemented bound to an acid in an organic compound.  These are referred to in chemistry terms as organic magnesium as they are organic compounds (chemistry "organic", not farming practice "organic").  These include magnesium ascorbate, aspartate, citrate, glutamate, lactate, malate, gluconate, fumarate, and glutamate. Of these, magnesium citrate is the most common in supplement form.  It is inexpensive and well absorbed, however, citric acid is mildly laxative and could pose issues for those with loose stool tendencies, not fun on a run. Magnesium malate is a good choice for those with fatigue or lacking energy  as malic acid, a fruit acid, is vital to enzymes critical to the process of ATP production.  Magnesium malate is highly soluble and therefore easily absorbed. Magnesium aspartate and magnesium glutamate contain amino acids that when not bound to other amino acids, can be neurotoxic. We do not recommend their use.


Finally, oral magnesium supplementation can also be achieved with amino acid chelates, where the magnesium is bonded to a nitrogen containing amino acid.  These tend to be pricier due to higher costs of production but the inclusion of the amino acid component creates an ability for additional absorption via protein digestion and metabolism pathways, enhancing overall absorption.  These are highly bioactive, generally, and are very well tolerated. The RunTheLabs favorite among them is magnesium malate as it is very well absorbed and poses little risk of gastrointestinal symptoms. Others include magnesium malate,especially for those with chronic sense of fatigue, lysine, orotate and taurate.  


In addition to oral supplementation, some mention is necessary of transdermal magnesium supplementation.  The use of Epsom salt baths is thought to promote transdermal magnesium absorption. As well, magnesium massage lotions and magnesium oil can be used topically as a way to bypass the digestive system and absorb magnesium directly into cells.  Direct application over sore muscles can be an effective way to reduce pain from muscle tension and cramping from training or low magnesium levels.


How we test:

We don't.  RunTheLabs likes the RBC(Red Blood Cell)  Magnesium test over the serum Magnesium test as it is a much more reliable indicator of body stores of the mineral.  However, due to the information above, we recommend you save your money on the test and just supplement magnesium at roughly the RDA levels.


We recommend 200-400 mg per day of Magnesium Malate per day, in divided doses, taken with food.  Say 100-200mg with breakfast, 100-200mg with dinner.

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