Magnesium: The Multi-Purpose Mineral
by Rehan Jalali
Magnesium is a versatile mineral that
has some major implications with regards to athletes. It has been studied
quite extensively in the research. This article tries to answer the question
"Why is magnesium so important to athletes and what are its functions?" By
exploring some general information on magnesium and then examining the
research, it may be clear to see why this mineral is so important for proper
Magnesium in the human body ranks fourth in overall abundance, but
intracellularly (within cells) it is second only to potassium. Between
60-65% of magnesium in the human body is found in bone. Magnesium that does
not exist as part of bone, is mainly found within muscle intracellularly
(1,2). About 1% of magnesium is found in the extracellular fluid. Inside
cells, magnesium may be found bound to phospholipids. In animal studies, it
has been shown that bone magnesium is used to maintain levels throughout the
body and muscle magnesium is maintained (3), when magnesium intake is
restricted. Magnesium absorption when ingested is carrier-mediated and is
influenced by transit time through the gut, dietary intake of magnesium, and
the amounts of phosphorous and calcium in the diet (4). These minerals
compete for absorption sites in the intestinal mucosa. Excess magnesium that
is not deposited in bone or retained in tissue is excreted through the
This mineral is involved in over 300 enzymatic reactions in the body (5)
including glycolysis, the krebs cycle, creatine phosphate formation, nucleic
acid synthesis, amino acid activation, cardiac and smooth muscle
contractability, cyclic AMP formation, and most importantly for strength
athletes, protein synthesis. Some of the functions of this important
macromineral are relevant to endurance and strength athletes. To fully
understand the implications this mineral has on athletes, we must explore
the roles of magnesium further.
ATP (adenosine triphosphate or energy) is always present as a magnesium:
ATP complex. Magnesium basically provides stability to ATP. Magnesium binds
to phosphate groups in ATP, thus making a complex that aids in the transfer
of ATP phosphate. Since working muscles generally contain more ADP
(adenosine diphosphate), allowing ATP to release a phosphate group is
important to exercising individuals.
Magnesium is also a cofactor to the enzyme creatine kinase which converts
creatine into creatine phosphate or phosphocreatine (which is the storage
form of creatine). Since creatine monohydrate supplements are extremely
popular and proven to be effective, magnesium may be an important mineral in
helping to optimize creatine function. In active muscle, creatine kinase
also helps phosphocreatine combine with ADP to resynthesize ATP in
contractile activity. This process, which involves magnesium, basically
increases anaerobic endurance. By the way, phosphocreatine possesses a
higher phosphate group transfer potential than ATP so it may be able to form
ATP quickly and provide energy for muscular activity (6).
Magnesium also plays an important role in protein biosynthesis which is
certainly applicable to athletes. It is necessary for the activation of
amino acids and the attachment of mRNA to the ribosome. This process helps
"make" proteins. In other words, protein synthesis depends on optimal
magnesium concentrations. It is hypothesized that low magnesium levels may
negatively affect protein metabolism, and may result in diminished strength
gains in a structured workout regimen. It is important to note that
increasing dietary protein intake may increase magnesium requirements
because high protein intake may decrease magnesium retention (5).
To completely understand magnesium function, it is necessary to explore
magnesium�s relationship with calcium and potassium. Magnesium is needed for
PTH (parathyroid hormone) secretion. PTH helps maintain calcium homeostasis.
High magnesium or calcium levels actually inhibit PTH secretion. Magnesium
may actually compete with calcium for nonspecific binding sites on myosin
(7). Magnesium may also cause an alteration in calcium distribution by
changing the flux of calcium across the cell membrane. It may also decrease
intracellular calcium concentrations by inhibiting the release of calcium
from the sarcoplasmic reticulum (7). In the process of blood coagulation,
magnesium and calcium are actually antagonistic. Calcium basically promotes
this process while magnesium inhibits it. If you take high amounts of
calcium daily, you may have a magnesium deficiency. Most experts suggest
that your calcium: magnesium ration should be 2:1. In other words, if you
take 1500 mg of calcium daily through diet and supplementation, you should
try to consume at least 750 mg of magnesium daily as well. this may help
prevent an imbalance from occurring. Magnesium and calcium supplements
should be taken at different times to allow for better absorption of each of
Magnesium and potassium also have a close relationship. Magnesium is
necessary for the function of the sodium/potassium pump. If a magnesium
deficiency occurs, then pumping sodium out of the cell and pumping potassium
into the cell may be impaired (5). Prescription diuretics tend to deplete
magnesium and potassium. In this situation, magnesium intake can normalize
both magnesium and potassium levels in the muscle (5).
Magnesium has also been implicated in the prevention of muscle cramps and
muscle spasms. In a clinical study, 500 mg of magnesium gluconate relieved
muscle spasms (within a few days) in an adult female tennis player who was
complaining about having muscle spasms associated with prolonged outdoor
exercise (8). This may be due to the fact that mineral losses through sweat
and urine are increased during prolonged exercise. In specific, sweat losses
of magnesium may increase during exercise (9). Increased loss of magnesium
from the body have been seen during and after exercise. A shift in magnesium
from the plasma into the erythrocytes was found (10). Basically , the more
anaerobic the exercise (i.e. glycolytic), the greater the movement of
magnesium from the plasma into the erythrocytes. This is why athletes may
have a greater magnesium requirement.
People who sustain heart attacks are usually magnesium deficient. There
are numerous studies which show that magnesium may be very important in
cardiac function (11,12,13,14). For example, one study (11) showed that the
early detection of magnesium deficiency is imperative for the prevention of
abnormal cardiac metabolism and the maintenance of structural integrity of
cardiac muscle during anaesthesia. The best way to get magnesium levels
tested by your doctor is to get magnesium levels tested in red blood cells
instead of serum. Testing magnesium levels in the serum will detect only the
most severe deficiencies.
So what does the research on magnesium with athletes say? One 1992 study
published in the Journal of the American College of nutrition entitled
"Effect of Magnesium Supplementation on Strength Training in Humans" (15)
studied the effects of a dietary magnesium supplement (magnesium oxide given
in a ratio of 8 mg/kg/day including dietary magnesium) on strength
development during a double-blind, 7 week strength training program in 26
untrained subjects. There was a magnesium supplemented group and a control
or placebo group. For example, a 200 lb. individual in the magnesium
supplemented group would receive about 725 mg of magnesium daily. The
results of the study showed that the oral magnesium supplementation group
produced significantly greater results in strength than the control group.
The researchers also concluded that magnesium�s role in protein synthesis
may be at the ribosomal level.
Magnesium is also an important mineral for endurance athletes. Endurance
athletes may become magnesium deficient because of increased magnesium
losses in sweat (16,17). Increased energy expenditure may also cause an
increase in magnesium requirements. Magnesium supplementation has also been
shown to improve cellular metabolism in competitive athletes (18). Another
clinical trial which studied the effects of magnesium supplementation (360
mg/day) for 4 weeks in male competitive rowers showed a decrease in serum
lactate concentration and oxygen consumption when compared to rowers
receiving a placebo (18). In other words, the results of this study
suggested that magnesium supplementation may have a beneficial effect on
energy metabolism and work efficiency.
Other research studies show that serum magnesium levels may be reduced in
response to strength training (19). Also, it has also been noted in research
studies that maximal contraction of the quadriceps is positively correlated
to serum magnesium status (20).
Alcoholism, renal disease, diabetes mellitus may all cause a magnesium
deficiency to occur. Some of the signs and symptoms of a magnesium
deficiency include nausea, vomiting, anorexia, muscle weakness, muscle
spasms, and tremors (6). Poor magnesium status may be related to
cardiovascular disease, hypertension, and heart attacks as mentioned
earlier. Regular magnesium levels in the red blood cells should be tested
for by a doctor every three months to help prevent any deficiency.
Magnesium toxicity is highly unlikely because normal kidneys can remove
magnesium extremely rapidly. Toxicity is more likely to occur in individuals
who have renal problems. One main effect of excess magnesium intake is
The best forms of supplemental magnesium seem to be the ones chelated to
an amino acid (magnesium glycinate, magnesium taurate) or a krebs cycle
intermediate (magnesium malate, magnesium citrate, magnesium fumarate).
These forms seem to be better utilized, absorbed, and assimilated. Try to
stay away from inorganic forms of magnesium like magnesium chloride or
magnesium carbonate because they may not be absorbed as well and may cause
Dietary fiber impairs magnesium absorption to a small extent (1) so
magnesium should not be consumed with any fiber source. Food sources of
magnesium include nuts, legumes, and soybeans. Since it may be impractical
for athletes to consume enough magnesium through dietary sources,
supplemental magnesium may be used. Taking 500-1000 mg/day of magnesium may
allow athletes to prevent any deficiencies as well optimize exercise
Athletes need to recognize the vital importance of this macromineral
since it plays a role in numerous bodily functions. So next time you
experience muscle spasms and/or muscle cramps or just want a boost in
strength, try magnesium supplementation and you may see some great results!
National Research Council. Recommended dietary allowances,
10th ed. Washington, DC: National Academy Press, 1989:187-194.
Shils ME. Magnesium. In: Brown ML,ed. Present Knowledge in
Nutrition, 6th ed. Washington, DC: International Life Sciences
Institute Nutrition Foundation, 1990: 224-232.
L. Brilla, et al., "Effect of hypomagnesemia and
exercise on slowly exchanging pools of magnesium," Metabolism 38
E. Hamilton, S. Gropper, The Biochemistry of Human
Nutrition (St. Paul, MN: West publishing, 1987).
P. Wester. "Magnesium," Am J Clin Nutr 45 suppl
Groff J, Gropper S, Hunt S. Advanced Nutrition and Human
Metabolism 2nd edition. (St. Paul, MN: West publishing, 1995).
L. Iseri, et al., "Magensium: Nature�s physiological
calcium blocker," Am Heart J 108 (1984): 188-193.
L. Liu, et al., "Hypomagnasemia in a tennis player,"
Phys. Sportsmed 11 (1983): 79-80.
C. Consolazio, et al., "Excretion of sodium, potassium,
magnesium, and iron in human sweat and the relation of each to balance and
requirements," J. Nutr 79 (1963): 407-415.
P. Deuster, et al., "Magnesium homeostasis during
high-intensity anaerobic exercise in men," J. Appl. Physiol. 62
B. Krasner, "Cardiac effects of magnesium with special
reference to anaesthesia: a review," Can Anaesth Soc J 26:3 (1979):
Y. Furkawa, et al., "Effects of magnesium on the
isolated, blood-perfused atrial and ventricular preparations of the dog
heart," Jpn Heart J 22:2 (1981): 239-246.
G. Stark, et al., "The influence of elevated Mg 2+
concentrations on cardiac electrophysiological parameters," Cardiovasc
Drugs Ther 3:2 (1989): 183-189.
M. Haigney, et al., "Tissue magnesium levels and the
arrhythmic substrate in humans," J Cardiovasc Electrophysiol 8:9
L. Brilla and T. Haley, "Effect of magnesium
Supplementation on on strength training in humans," J. Amer. Coll.
Nutr. 11.3 (1992): 326-329.
D. Costill, et al., "Muscle water and electrolytes
following various levels of dehydration in man," J. Appl. Physiol.
40 (1976): 6-11.
R. McDonald and C. Keen, "Iron, zinc, and magnesium
nutrition and athletic performance," Sports Med. 5 (1988): 171-184.
S. Golf, et al., Is magnesium a limiting factor in
competitive exercise? A summary of relevant scientific data. In Magnesium
(London: John Libbey & Company, 1993), pp. 209-220.
F. Beuker, et al., "The saturation of magnesium plasma
levels during strength training," Magnesium Res. 2 (1989): 294.
G. Stendig-Lindberg, et al., "Predictors of maximum
voluntary contraction force of quadriceps femoris muscle in man. Ridge
regression analysis," Magnesium 2 (1983): 93-104.