Magnesium supplementation in top athletes - effects and recommendations

Abstract

Magnesium is a cofactor involved in many enzymatic systems, being necessary for protein synthesis, functioning of nervous and muscular systems, regulation of blood pressure and glycaemia, bone metabolism. A low dietary intake of magnesium is very common in general population. Additionally, there are categories of population that are even more predisposed to hypomagnesaemia. Top athletes represent a population category predisposed to magnesium deficiency due to increased urinary and sudorific losses, and in case of heavyweight disciplines, due to a decreased dietary intake. Many studies supported the role of magnesium in athletic performance and showed that magnesium increased the physical endurance and improved the force indices and muscle metabolism in athletes that had a rich diet in magnesium or received magnesium supplements. It is still uncertain whether the positive effects of magnesium supplementation in athletic performance are due to pharmacological actions of magnesium itself or to the reversal of a preexisting magnesium deficiency. Therefore, the purpose of this article is briefly review of Magnesium importance in human health and athletics performance, various hypotheses that may explain magnesium's physiologic action mechanisms but also possible pathways for magnesium deficiency’s correction.

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Magnesium supplementation in top athletes - effects and recommendations
Adriana Sarah Nica¹, Adela Caramoci², Anca Mirela Ionescu², Denis Paduraru³, Virgil Mazilu³
¹ University of Medicine and Pharmacy “Carol Davila”, Departament of Rehabilitation, Bucharest
² University of Medicine and Pharmacy “Carol Davila”, Departament of Sports Medicine, Bucharest
³ National Institute of Sports Medicine, Bucharest
Abstract. Magnesium is a cofactor involved in many enzymatic systems, being necessary for protein synthesis,
functioning of nervous and muscular systems, regulation of blood pressure and glycaemia, bone metabolism. A
low dietary intake of magnesium is very common in general population . Additionally, there are categories of
population that are even more predisposed to hypomagnesaemia. Top athletes represent a population category
predisposed to magnesium deficiency due to increased urinary and sudorific losses, and in case of heavyweight
disciplines, due to a decreased dietary intake. Many studies supported the role of magnesium in athletic
performance and showed that magnesium increased the physical endurance and improved the force indices and
muscle metabolism in athletes that had a rich diet in magnesium or received magnesium supplements. It is still
uncertain whether the positive effects of magnesium supplementation in athletic performance are due to
pharmacological actions of magnesium itself or to the reversal of a pre-existing magnesium deficiency.
Therefore, the purpose of this article is briefly review of Magnesium importance in human health and athletics
performance, various hypotheses that may explain magnesium's physiologic action mechanisms but also possible
pathways for magnesium deficiency’s correction.
Key words: magnesium, athlete, deficiency, supplementation.
Some basics of Magnesium
Magnesium is the second most abundant mineral in cells after potassium, but the two ounces or so found in the
typical human body is present not as metal but as magnesium ions (positively-charged magnesium atoms found
either in solution or complexed with other tissues, such as bone). Roughly one quarter of this magnesium is
found in muscle tissue and three-fifths in bone; but less than 1% of it is found in blood serum, although that is
used as the commonest indicator of magnesium status. This blood serum magnesium can be further subdivided
into free ionic, complex-bound and protein-bound portions, but it's the ionic portion that's considered most
important in measuring magnesium status, because it is physiologically active.
The importance of magnesium as an essential nutrient has been emphasised as early as 1932 by Kruse et al., who
induced an acute magnesium deficiency in rats by limiting the dietary intake of this element to
0.09mEq/kilogram. Hypomagnesaemia produced hyperemia, neuromuscular progressive irritability that
eventually precipitated fatal convulsions in these animals (1).
The role of Magnesium in the Body
Mg is a cofactor involved in many enzymatic systems (more than 300 biochemical reactions), being necessary
for protein synthesis, functioning of nervous and muscular systems, regulation of blood pressure and glycaemia,
bone metabolism (2-4). Most studies regarding magnesium metabolism and homeostasis have shown that
magnesium interferes with transmembrane sodium and potassium ion flow in smooth muscle, which explains its
involvement in many physiological processes and why magnesium deficiency is linked to many pathological
conditions of the cardiovascular, skeletal and nervous systems(5-7). It also affects the active transmembrane
transport of calcium and potassium ions, being a known calcium-channel blocker, and through these processes
influences nerve conduction, muscular contraction and cardiac rhythm (4).
Its presence is necessary for both aerobic (oxidative phosphorylation) and anaerobic (glycolysis) energy
production processes, both indirectly, as a component of ATP-Mg complex and directly, as an enzymatic
activator (8).
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It plays an important role in cell division, participating in DNA, RNA and glutathione synthesis (9).
It is essential in osteoblasts and osteoclasts functioning, vitamin D activation, calcitonin release and suppression
of parathyroid hormone release (10). Magnesium depletion disturbs calcium homeostasis, hypocalcaemia being
sometimes determined by a moderate or severe deficiency of Mg. The inadequate intake of magnesium
stimulates extracellular depositions of calcium (calcifications). Although Mg deprivation increases intestinal
absorption and renal reabsorption via a still unknown mechanism, if this process continues, Mg in bones will
play a major role in maintaining a normal extracellular level of magnesium and up to 30% of intra osseous
magnesium can be mobilized for this purpose. Research has shown that it is important to maintain an optimal
ratio between calcium and magnesium intake, whose ideal value is 1:1. These mechanisms can explain the
significant correlations between magnesium level and bone density, published by some authors (11, 12) and why
they recommend Mg supplementation for menopausal women as a way to prevent osteoporosis (13).
A group of researchers from the Department of Cognitive Sciences of the Massachusetts Institute of Technology
has shown that Magnesium regulates the activity of a key receptor involved in memory and learning processes
and that a normal level of Magnesium in the cerebrospinal fluid is essential for maintaining the plasticity of the
cerebral synapses. The authors claimed that an increase of magnesium level in the brain would ameliorate the
cognitive processes and memory (14). In fact, the authors of an earlier study (1996) also reported positive effects
after magnesium administration to children with ADHD. These effects were attributed to an improvement in
cerebral activity and a sedating effect of magnesium on CNS (15).
Recommended dietary allowances for Magnesium and sources of magnesium
The UK recommended intake for magnesium (the daily amount deemed adequate to prevent deficiencies in
97.5% of the UK population) is set at 300 mgs for men and 270 mgs for women (16). The US has recently
revised its figures upwards and now recommends an intake of 400 mgs per day for men aged 19-30 and 420 for
those over 30; the figures for women under and over 30 are 300 and 310 mgs per day respectively (17).
However, some investigators believe these should be set even higher at 450-500mg/day (18).
Daily allowance of magnesium has been set by the Institute of Medicine in Washington in terms of age and sex
(see table I) (19).
Table I. Recommended Dietary Allowances (RDAs) for Magnesium [1]
Age Male Female Pregnancy Lactation
Birth to 6 months 30 mg* 30 mg*
7–12 months 75 mg* 75 mg*
1–3 years 80 mg 80 mg
4–8 years 130 mg 130 mg
9–13 years 240 mg 240 mg
14–18 years 410 mg 360 mg 400 mg 360 mg
19–30 years 400 mg 310 mg 350 mg 310 mg
31–50 years 420 mg 320 mg 360 mg 320 mg
51+ years 420 mg 320 mg
Institute of Medicine (IOM). Food and Nutrition Board. Dietary Reference Intakes: Calcium, Phosphorus,
Magnesium, Vitamin D and Fluorideexternal link icon. Washington, DC: National Academy Press, 1997.
*Adequate Intake (AI)
Foods with increased content of fibres, such as vegetables, spinach, seeds, nuts and whole grains are reach
sources of magnesium (4). Fruit, meat and fish supply poor levels, as do refined foods. Magnesium is a fairly
soluble mineral, which is why boiling vegetables can result in significant losses; in cereals and grains, it tends to
be concentrated in the germ and bran, which explains why white refined grains contain relatively little
magnesium by comparison with their unrefined counterparts (20). Contrary to common belief, milk and dairy
products are not particularly rich sources of magnesium. The magnesium content of plant foods tends to reflect
soil magnesium concentrations and growing conditions, especially as magnesium is not routinely added to soils
by farmers during intensive fertilization (21).
Water also contains magnesium in different proportions from 1/mg/l to more than 120 mg/l (22).
From the total dietary intake of magnesium, only 30-40% is intestinally absorbed (3).
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Magnesium Deficiencies
Many people fall short of optimum magnesium intakes, and this has been confirmed in a number of studies.
Dietary intakes of magnesium in the United States have been declining over the last 100 years from about 500
mg/day to 175-225mg/day (23) and amore recent national survey suggested that the average magnesium intake
for women is as low as 228mgs per day (24). But since this figure is derived using a one-day diet recall method,
it may actually be an overestimate of actual magnesium intakes (25). American researchers found that more than
60% of US adults were failing to meet even the previous (lower) RDA for magnesium (26).Recent data provided
by the National Health and Nutrition Examination Survey (NHANES) have shown that the diet of most
Americans included suboptimal levels of magnesium, except for those who took magnesium supplements (27,
28).Another study published in 2005, showed that 2/3 of Americans have a dietary intake of magnesium below
the recommended minimal level, 19% of them even below half of this level (29). Meanwhile, the UK's Food
Standards Agency estimates that the average daily intake of magnesium in Britain for both men and women is
just 227 mgs - only two thirds of the US recommended daily amount (RDA).
Risk groups for magnesium deficiency. Although magnesium is considered an effective treatment for many
severe diseases, (diabetes, asthma, high blood pressure, metabolic syndrome, preeclampsia and eclampsia, etc.),
it is still uncertain whether the positive effects of magnesium supplementation in these medical conditions are
due to pharmacological actions of magnesium itself or to the reversal of a pre-existing magnesium deficiency,
responsible for their etiology or pathogenesis. This hypothesis is very probable, since a low dietary intake of
magnesium is very common in general population. Additionally, there are categories of population that are even
more predisposed to hypomagnesaemia, because magnesium homeostasis involves the intestine, kidney and
osseous system, and the physiological disturbances of these organs affect magnesium metabolism (30).
Magnesium absorption takes place mostly in jejunum and ileum via an active transcellular diffusion process and
a passive mechanism mediated by a cationic electrochemical gradient. Intestinal malabsorption caused by
Chron’s disease, celiac disease, enteritis and surgical removal of small intestine, especially ileum (small bowel
syndrome), can induce hypomagnesaemia (3). The proton pump inhibitors, used to treatment of hyperacidic
gastritis, gastric and duodenal ulcer and gastro-esophageal reflux can produce hypomagnesaemia, too (31-34).
Renal function also influences significantly magnesium metabolism. Kidneys filtrate approximately 2.4 g/day of
Mg, but most of it is reabsorbed and only 5% is normally excreted in urine. Diuretics can affect the level of
magnesium; loop and thiazide diuretics decrease magnesium level, due to an increased urinary excretion, while
K+ sparing diuretics (amiloride and spironolactone) augment it, due to an increased renal reabsorption (35).
Diabetes mellitus can secondarily produce a magnesium deficit by increasing the urinary losses of magnesium
(36, 37).
Older people also represent a population category with an increased risk for inadequate levels of magnesium,
due to a reduction of intestinal absorption and an increased renal excretion as compared to younger population
(38). Furthermore, thelong-term use of medicationin many aged patients interferes with magnesium homeostasis
(39).
Alcoholism reduces the plasma level of magnesium through mechanisms that involves both a decrease in
intestinal absorption due to pancreatitis and hepatic steatorrhoea and increased urinary excretion due to a renal
dysfunction. Other possible mechanisms are secondary hyperaldosteronism caused by a hepatic dysfunction,
phosphorus and Vitamin D deficiency, ketoacidosis, etc. (40).
As we will show further on, top athletes also represent a population category predisposed to magnesium
deficiency due to increased urinary and sudorific losses, and in case of heavyweight disciplines, due to a
decreased dietary intake.
Medical conditions associated with magnesium deficiency. The symptoms of an early magnesium deficiency are
nausea, vomiting, fatigue, headache, insomnia, confusion, irritability, muscle weakness, while an advanced
hypomagnesaemia produces muscle cramps, paresthesia, cardiac arrhythmia and coronary spasm. A very low
level of magnesium generates severe hypocalcaemia and hypokalaemia that can be corrected only through
simultaneous administration of magnesium (3, 4).
A few scientific studies published in the early 1980s supported a possible involvement of magnesium deficiency
in coronary spasm, due to an effect on vessel smooth muscles (41). Many subsequent studies have found
significant correlations between inadequate levels of magnesium and various cardiovascular pathological
conditions such as high blood pressure, ischemic heart disease and arrhythmia (42-46). An epidemiological study
that followed the evolution of 12000 subjects over a period of 19 years showed an inverse relationship between
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magnesium plasma concentration and mortality rate produced by ischemic vascular diseases , data suggesting
that the subjects with the highest level of plasmatic magnesium had a 30% lower risk of developing heart disease
(47).
Hypomagnesaemia has also been linked to diabetes mellitus due to the role that magnesium plays in maintaining
glycaemia and diminishing resistance to insulin (48-50). Although American Diabetes Association considers that
there are no convincing proves to include magnesium in the treatment of diabetes mellitus (51), many studies
have demonstrated that magnesium had a positive effect on decreasing glycaemia in diabetics (50- 53).
Bronchial asthma has also been correlated with inadequate levels of magnesium (54, 55) and a couple of recent
studies supported the positive effect of Mg supplementation on bronchial asthma, due to a decrease of bronchial
mucosa sensitivity in children (56, 57).
Magnesium has been proposed for prophylaxis of migraine crisis, the positive effects being due to its
involvement in the vasoconstriction/vasodilation processes and release of neurotransmitters (58- 60).
The use of magnesium in treatment of depression is still uncertain, but a low level of magnesium has been
associated with a low level of serotonin (61, 62).
The role of Magnesium in athletic performance
Magnesium effect on energy production. Magnesium has been one of the most used supplements for enhancing
athletic performance (63). Many studies supported the role of magnesium in athletic performance and showed
that magnesium increased the physical endurance (64, 65) and improved the force indices and muscle
metabolism in athletes that had a rich diet in magnesium or received magnesium supplements (66).
Magnesium’s pivotal role in both anaerobic and aerobic energy production, particularly in the metabolism of
adenosine triphosphate (ATP), the “energy currency” of the body. The US researchers concluded that low dietary
magnesium impairs function during exercise. The mechanisms behind this effect are unclear, but it seems likely
that a magnesium shortfall can cause a partial uncoupling of the respiratory chain, increasing the amount of
oxygen required to maintain ATP production. There is also evidence that a magnesium shortfall boosts the
energy cost, and hence oxygen use of exercise because it reduces the efficiency during exercise of muscle
relaxation, which accounts for an important fraction of total energy needs during an activity like cycling (67).
One study of male athletes supplemented with 390 mgs of magnesium per day for 25 days resulted in an
increased peak oxygen uptake and total work output during work capacity tests (68); in another, on sub-maximal
work, supplemental magnesium elicited reductions in heart rate, ventilation, oxygen uptake and carbon dioxide
production (69); in a third, physically active students, supplemented with 8 mgs of magnesium per kilo of body
weight per day, experienced significant increases in endurance performance and decreased oxygen consumption
during standardized, sub-maximal exercise (70).
As a results of some studies performed on gerbils, the authors noticed that, when compared to control a group,
the group of animals that received parenterally a solution of magnesium sulphate had an increased length of
physical performance and also experienced increased levels of glycaemia and decreased levels of lactate
production during exercise, effects that were attributed to magnesium (71, 72).
A recent study on the use of magnesium in 1,453 adults demonstrated that higher serum (blood) magnesium
levels were associated with better muscle integrity and function. This included grip strength, lower-leg muscle
power, knee extension torque and ankle extension strength. These results highlight the importance of magnesium
for improving muscle function and performance (73).
An earlier study showed that a magnesium supplementation of 8 mg/kg associated to a strength training at 3
times per week produced a significantly larger increase in strength compared to the control group that followed
the same training protocol, but without magnesium supplementation. The authors concluded that the result was
due to the role that magnesium plays in protein synthesis at the level of ribosomes (74).
An increase of strength indices can be due to the stimulation of testosterone secretion that was induced by
physical training. A 2011 study showed that a dose of magnesium of 10mg/kg produced a greater increase of
testosterone level in a group of tae kwon do athletes, when compared to the control group that didn’t receive the
supplement.At the end of the study, the authors concluded that magnesium administration produced an increased
level of testosterone both in sedentary and trained subjects, but the maximal increase was noticed when
magnesium supplementation was associated with training (75).
However, other studies carried out on physically active people with 'normal' serum magnesium and muscle
magnesium concentrations have found no functional or performance improvements associated with
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supplementation (76, 77). On the evidence available so far, the scientific consensus is that extra magnesium can
enhance performance when (as is all too often the case) magnesium intakes fall below optimum levels. But in
subjects already consuming magnesium at or above this optimum level, there is little hard evidence to suggest
that taking more confers extra benefits.
The negative influence that magnesium depletion has it on athletic performance can also be explained by its
effect on body composition. In this respect, we mention the fact that a group of Japanese researchers claimed
that there is a correlation between magnesium level and body fat percent, reporting that increased body mass
indices had a statistically significant association to low level of magnesium (78). In fact, a few authors stated
that a deficit of magnesium is involved in pathogenic mechanisms of the Metabolic Syndrome, characterized by
the triad of obesity, diabetes mellitus and hypercholesterolemia, through a pro-inflammatory effect, but this
effect manifests itself only when magnesium daily intake is below 10% of normal. Although a moderate deficit
of magnesium does not initiate an inflammatory process, it has an aggravating effect, especially when a
simultaneous oxidative stress is present (79). Many studies have found correlations between the deficit of
magnesium and the C reactive protein level, a marker of inflammation (80, 81).
Magnesium effect on postexercise recovery.An inadequate level of magnesium can affect the recovery after
exercise and the process of a normal adaptation to effort.
A hyperactivity of the sympathetic system, induced by a magnesium deficit, produces an increased release of
norepinephrine and cortisol, which represents a defective adaptation to physical exercise that normally needs a
strong vagal tonus. A study published in 2009 by Kazuto Omiya et al. concluded that the abnormal exercise
tolerance associated with chronic insomnia is caused by a hypersensitivity of cardiac rhythm to sympathetic
system stimulation, which appears as a result of a decreased intracellular magnesium (78).Other authors also
claimed that an optimal level of magnesium in the body is correlated with a reduction in sympathetic system
activity, low stress level, good relaxation and better sleep (82).
Although it does not support the idea of a positive effect of magnesium supplements on athletic performance, a
2013 study reported a decreased postexercise blood pressure, both in anaerobic and aerobic exercise (83).
Furthermore, the link between magnesium deficiency and a low sensitivity to insulin suggests a defective
replenishment of glycogen stores in hypomagnesaemia and, through this mechanism, an inadequate postexercise
recovery in athletes that present this disequilibrium.
Magnesium is necessary for normal muscular contraction and relaxation. Low magnesium levels are associated
with an increased incidence of muscle cramps, which can often be reversed with the addition of magnesium
supplements. In one research trial, swimmers taking magnesium supplements during their training and
competitions found an 86% reduction in muscle cramps. The reductions occurred after only three days of
supplementation (73).
Magnesium deficiencies in athletes. Even athletes, who might be expected to take greater care with their diets,
are not immune from magnesium deficiency; for example, studies carried out in 1986/87 revealed that gymnasts,
footballers and basketball players were consuming only around 70% of the RDA (84, 85), while female runners
fared even worse, with reported intakes as low as 59% of the RDA (86).
Some authors claim that the positive results of magnesium supplementation on athletic performance a reduce to
a correction of magnesium deficit that characterizes top athletes and less to a magnesium effect per se (65).
There are couple of scientific studies that claim that the decrease of magnesium is a metabolic modification
induced by a sustained physical training. An analysis performed in Israel on metabolic effects of an intense
training carried out over a period of 6 months, showed that the study subjects presented modifications of more
metabolic parameters, the decrease of magnesium serum concentration being considered a primary modification.
It’s worth noticing the that the level of magnesium didn’t change immediately after the race, but only 72 hours
later and remained reduced over a long period of time, which varied between 18 days and 3 months (87).
In their analysis regarding the relationship between magnesium and physical exercise, published in 2006,
Nielsen and Lukaski warned that physical exercise induces a redistribution of magnesium in the body to
accommodate increased metabolic needs. Urinary and sweat losses increase the requirements of magnesium in
athletes who train strenuously by more than 10-20%.Dietary intake of magnesium in general population is
considered insufficient for these athletes. In addition, the athletes that participate in heavyweight categories (e.g.,
weightlifting, boxing, etc.,) but also the female gymnasts, whose performance require a low body weight, are
even more predisposed to magnesium deficiency, due to a low intake caused by a caloric restriction (65).
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Magnesium supplementation may produce improvement of athletic performance by correcting the low status of
magnesium in athletes, which is associated with an increased demand of oxygen for the same effort and a
decreased exercise endurance. The same authors consider that in athletes the risk of hypovitaminoses, especially
for fat soluble vitamins, is much smaller than the risk of mineral deficiency (88).
Bohl and Volpe, in their analysis concerning magnesium involvement in physical exercise, published in 2002,
also showed that the dietary reference intakes for magnesium, in amount of 310-420 mg/day, are insufficient for
those who participate in physical training and enumerated a couple of studies that claimed that magnesium
improves athletic performance (89). On the other hand, regarding the direct effect of magnesium on athletic
performance, a recent study (2014) has showed that magnesium supplementation produced an increase of
performance indices in volleyball players, even in those athletes who hadn’t had low levels of magnesium (90).
Magnesium deficiency and sudden death risk in athletes.
Of paramount importance regarding the predisposition of top athletes to inadequate levels of magnesium is the
association of hypomagnesaemia with an increased risk of sudden death by favouring arrhythmias (91). It is well
known that this risk is higher in top athletes than in general population (92). Stendig and Lindberg stated
thatsudden death in athletes during physical exercise is linked to a persistent deficit of magnesium (93).
Endurance running, due to excessive sweat losses, can induce a severe deficiency of magnesium towards the end
of the race, increasing significantly the risk of a serious arrhythmia (94).
Testing For Magnesium Status
Our body contains approximately 25 g of Mg out of which 50-60% lies in bones, 27% in musculature, 19% in
other soft tissues and less than 1% in plasma (95). Intracellular Mg is mostly bound by chelators, such as ca ATP,
ADP, proteins, DNA, RNA and citrate. Physiological concentrations range between 0.75 and 0.95mmol/l (96), a
blood value below 0.75 mmol/l being considered hypomagnesaemia (97).
Since only 0.3% of the total Mg is present in serum, magnesium serum concentration is considered a poor
indicator of Mg status. There have been proposed many methods to investigate the level of Mg in the body, such
as measuring its concentration in saliva and urine, Mg load tolerance tests, etc., but none was considered
satisfactory (98). Most experts agreed that a correlation between clinical manifestations and lab values could be
the best way to diagnose hypomagnesaemia (99).
Total blood magnesium (TMg) is the most widely used assay, but this has the disadvantage of including complex
and protein-bound magnesium, whereas it's the ionic portion that's physiologically active. This test is also
insensitive to the movements of magnesium that occur within the body as a result of exercise.However, the
recent introduction of ion-selective electrode (ISE) technology now enables scientists to measure ionic
magnesium directly, and this is considered one of the best methods. But even then it's not all plain-sailing, since
ionic magnesium levels tend to fluctuate significantly according to the time of day, with higher values recorded
in the morning and lower values in the evening.This 'circadian magnesium rhythm' is believed to be linked to
changes in physical activity levels through the day, but the whole subject of 'intra-body' magnesium fluctuations
remains poorly understood. Nevertheless, the best results seem to be obtained when ionic magnesium is sampled
from fasting, non-exercised subjects first thing in the morning (100).
Magnesium Supplementation
Oral Supplementation. IOM (Institute of Medicine) recommendations regarding the amount of Magnesium that
can supplement the dietary intake for healthy persons are presented in table II (19). These recommendations
were made in 1996 and they should be updated since current dietary intake,due to an intensive agricultural
production and an increased processing of food,contains increasingly smaller amounts of this element,which is
essential for the normal functioning of the human body.
Although oral supplementation of Mg is possible, the processes of remineralisation and replenishment of
intracellular and extracellular Mg take time and are influenced by many factors. An inversely proportional
relationship has been described between magnesium intake and its rate of absorption, which varied between 65%
(in case of a low intake of magnesium) and 11% (high ingestion). When a high dose of magnesium is
administered, there is another factor that interferes with Mg absorption, namely an accelerated intestinal transit,
due to an increased osmolarity and stimulation of peristalsis (101). In addition, concomitant administration of
other mineral supplements, such as zinc or calcium, can negatively intestinal absorption rate of Mg.
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The inexpensive oral supplements of magnesium generally contains magnesium oxide, which is poorly absorbed
(4%).Magnesium citrate is much better absorbed (50%), but is not so cheap. Out of a daily intake of 300-400 mg
elemental Mg, only an amount of 12-16 mg can be used (the ionized form). A few studies showed that soluble
preparations are generally better absorbed and magnesium aspartate, citrate, lactate and chloride have a superior
bioavailability compared to magnesium oxide and sulphate (104-108).
Table II. Tolerable upper intake levels (ULs) for supplemental Magnesium [19]
Age Male Female Pregnant Lactating
Birth to 12 months None established None established
1–3 years 65 mg 65 mg
4–8 years 110 mg 110 mg
9–18 years 350 mg 350 mg 350 mg 350 mg
19+ years 350 mg 350 mg 350 mg 350 mg
Institute of Medicine (IOM). Food and Nutrition Board. Dietary Reference Intakes: Calcium, Phosphorus, Magnesium,
Vitamin D and Fluorideexternal link icon. Washington, DC: National Academy Press, 1997.
Topical Supplementation. Topical or transdermal administration of magnesium is an interesting alternative to
oral route, considering the many interferences in the absorption of magnesium oral supplements. Transdermal
magnesium is applied topically, using either magnesium lotions or magnesium bath salts.
The local effect on mucosae and skin is well documented. There have been some studies that showed the
positive effects of nebulized magnesium sulphate on bronchial asthma (109) and on skin cells proliferation and
differentiation (110). In fact, some of the benefits of Dead Sea bath salts are attributed not to the high content of
salt, but to magnesium itself, the prevalent cation of Dead Sea water (111). Comparative studies regarding the
effects of a solution whose salinity was similar to that of Dead Sea water, showed cleared benefits over a normal
saline solution, both in the treatment of ENT conditions (such as chronic sinusitis) (112) and rheumatoid arthritis
(113).
The hypothesis of topical supplementation of magnesium, although appealing, faces a challenge: transdermal
diffusion of magnesium or its salts. Unfortunately, there are few studies in scientific literature concerning
transdermal absorption of magnesium. We are of the opinion that the benefits obtained in the treatment of
rheumatoid arthritis, using solutions with a high content of magnesium, represents a strong argument that
magnesium effectively crosses the skin barrier.
In an earlier study (1977), a couple of authors verified the transdermal absorption of a Magnesium Sulphate
solution, of various concentrations, applied on skin for 8 hours . The results showed that the transdermal
absorption of magnesium increased linearly with solution concentration and skin surface area (114). More
recently, Dr R.H. Waring et al., from the University of Birmingham, School of Biosciences, have published an
online study regarding transdermal absorption of magnesium after daily baths with Epsom Salt (1% solution of
Magnesium sulphate). Each daily bath lasted for 12 minutes, over a period of 7 days. Plasmatic concentrations of
magnesium were determined before and at 2 hours after hydrotherapy, while urinary concentration of
magnesium was measured at 24 hours post immersion. The results showed an increase of magnesium plasma
concentrations from 104.68 ± 20.76 ppm/ml before experiment to 114.08 ± 25.83 ppm/ml after the first bath.
Plasmatic concentration of magnesium increased progressively over the course of treatment, reaching 140.98 ±
17.00ppm/ml after 7 days. The author concluded that body immersion in a solution of magnesium sulphate
caused an increase in plasmatic concentration of magnesium. The renal excretion of magnesium increased
significantly after the first day, from an initial value of 81 ± 44.26 ppm/ml to 198.93 ± 97.52 ppm/m at 24 hours
after the first bath. The greatest increases of urinary excretion of magnesium were recorded in those subjects
who presented the smallest increases of plasmatic magnesium, and the author hypothesized that in these subjects
magnesium ions that crossed the skin barrier were excreted, because the plasmatic level of magnesium had
already been optimal. However, urinary excretion of magnesium decreased over the course of 7 days, so that at
the end of the 7th day it reached values similar to those recorded at the beginning of the treatment (118.43 ±
51.95), although the plasma level increased, implying that after an extended application of transdermal
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magnesium, this mineral accumulates in the body. The study recommended a protocol of 2-3 baths a week, in a
solution of 1% MgSO4 (that is 600mg in 60 l water), for a maximal benefit of general population. The study
concluded that magnesium sulphate (Epsom salt) baths are an easy and certain method to increase magnesium
level in the body (114).
A pilot study published by Watkins K and Josling PD, initially in European Journal for Nutraceutical Research,
in April 2010 and then in “The nutrition Practitioner” and called “A pilot study to determine the impact of
transdermal magnesium treatment on serum levels and whole body Ca-Mg ratio” also asserts that magnesium
effectively crosses the skin barrier. The authors showed that transdermal application of a 31% magnesium
chloride formulation could alter serum magnesium levels and whole body calcium/magnesium ratios. After 12
weeks’ treatment 89% of subjects increased their cellular magnesium levels by 59.7% on the average.Similar
results using oral supplementation were noticed only after 9-24 months (115).
An aqueous solution of magnesium chloride, also known as “magnesium oil” is used as a massage lotion for
treating headache and muscle cramps, and certain authors claim that the absorption of this solution is good
enough to be used as a treatment for magnesium deficiency.
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Corresponding author
Adela Caramoci
University of Medicine and Pharmacy “Carol Davila”
Department of Sports Medicine
Bucharest, Romania
E-mail: adelaapostol@yahoo.com
Received: December 10, 2014
Accepted: February 25, 2015
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