Magnesium

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What is magnesium?

Magnesium is a chemical element, a metal, with the symbol "Mg" and atomic number 12.

It constitutes the eleventh most abundant element in the human body and is essential for all tissues and cells; structure approximately 300 enzymes. Magnesium ions interact mainly with polyphosphate compounds, for example ATP (since in these processes the active form of ATP is complexed with magnesium ion Mg ++), DNA and RNA; they constitute the skeleton, they intervene in the regulation of the excitability of the nervous and muscular membranes, and in the synaptic transmission.

The human body contains over 20 g of magnesium, which corresponds to 0.35 g / kg, or 0.34% of body mass. Combined with calcium and phosphorus, magnesium is an essential constituent of hydroxyapatite - the structural mineral of bone tissue. About 60-65% of the body's total magnesium is found to be mineralized in the skeleton. A minority share, however, very important from a biological point of view, is located in intracellular fluids and plasma. 32-35% of magnesium is complexed to proteins and nucleic acids, while only 1-2% in plasma and other minor forms of deposition.

Magnesium-based formulas are used in the pharmacological industry to synthesize laxatives, antacids - for example the well-known "magnesia milk" - stabilizers of certain nervous anomalies and remedies against eclampsia.

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Magnesium also reacts exothermically with most acids such as hydrochloric acid (HCl), producing metal chloride and hydrogen gas, similar to the reaction between HCl and aluminum, zinc and many other metals. It is this reaction that justifies its use as an antacid in drugs.

Plant foods, such as oily and starchy seeds and vegetables, are food sources of magnesium. The lack, not frequent in healthy, sedentary people who follow a balanced diet, is instead possible in subjects with accentuated sweating, in endurance athletes - independently from the latter factor - in the presence of severe dysentery and functional pathologies of the kidneys and / or endocrine. Magnesium deficiency, in the physiological field, is identified with muscle cramps, weakness, fatigue and asthenia. There are various types of food supplements based on magnesium, to be taken especially in the doubt that nutrition is not sufficient to cover the needs. The excess is rare and, generally, also linked to functional pathologies of the kidneys, of the hormonal axis and to the taking of drugs that contain it.

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Biological Role

Magnesium biological role

The interaction, to say the least fundamental, between phosphate and magnesium ions makes this essential to the biochemistry of the nucleic acids of all known living cells. Over 300 enzymes require the intervention of magnesium ions to perform their catalytic action, including those that use or synthesize ATP and those that use other nucleotides to synthesize DNA and RNA. The ATP molecule is normally found in a chelated form with a magnesium ion.

Metabolism

Magnesium metabolism

An adult organism contains about 22-26 g of magnesium, of which 60% is found in the skeleton, 39% in the cells - 20% in the striated muscles - and 1% in the extracellular spaces. Serum magnesium levels are generally 0.7-1.0 mmol / liter - 1.8-2.4 mEq / liter - and remain in homeostasis even when the intracellular fraction is deficient.

The presence of intracellular magnesium is closely related to that of potassium. A possible increase helps to reduce calcium levels and can prevent hypercalcaemia or even cause hypocalcemia - depending on the initial level.

The magnesium metabolism is significantly influenced by the parathyroid hormone, but the following are mainly involved in ensuring the stability of blood levels: absorption management and excretion.

Magnesium detection in serum and plasma

The nutritional status specifically referred to the magnesium intake can be evaluated by measuring the concentrations of the same in serum and erythrocytes, and the urinary and fecal content. However, intravenous magnesium loading tests remain more accurate and practical. A retention equal to or greater than 20% of the injected indicates an actual deficiency. No biomarker is known.

Plasma or serum concentrations of magnesium can be monitored to determine the efficacy or safety of some drug therapies, to confirm the diagnosis in potential poisoning victims or to verify a fatal overdose. Infants of mothers who have received magnesium sulfate parenterally during labor may present toxicity even with normal serum magnesium levels.

Absorption and Excretion

Magnesium absorption and excretion

Magnesium absorption occurs mainly in the small intestine, is favored by the plasma content of vitamin D but is hindered by some nutritional concentrations. In particular, both the excess and the lack of proteins play an inhibitory function on ion uptake, as well as the presence of phytic acid and oxalic acid, or the excess of phosphates, calcium and fat. Unabsorbed magnesium is excreted in the faeces. Note : only 30-40% of the magnesium present in food is absorbed by the body. For more information, see the article dedicated to the absorption of magnesium: Magnesium absorption - Diet and supplements.

The excretion of magnesium occurs mainly in the urine, by renal filtration, and by sweating. The importance of the latter may vary depending on the entity.

Food

Magnesium in foods

Those of vegetable origin are foods rich in magnesium, such as starchy and oily seeds - such as legumes (borlotti beans, soybeans, azuki, from the eye, lentils, chickpeas, broad beans, peas, lupins, etc.) - dried fruit (walnuts, almonds, etc.), cocoa, whole grains (wheat, rice, rye, etc.). Magnesium also abounds in some spices, in sweet fruits and vegetables, especially with green leaves, since it is a fundamental constituent of chlorophyll (spinach, lettuce, rocket, green chicory, etc.).

We reiterate again that only 30-40% of the magnesium present in food is absorbed by the body. For more information, see also: Food with magnesium.

Diet

Magnesium requirement

The daily magnesium requirement for adult men amounts to 300-500 mg, but increases significantly in particular conditions such as: increased sweating, diarrhea, vomiting, renal impairment, drug therapies such as antihypertensive diuretics, certain antibiotics, etc.

In the United Kingdom, the recommended daily values ​​for magnesium are 300 mg for men and 270 mg for women. In the United States the recommended dietary doses (RDA) are 400 mg for men aged 19-30 years and 420 mg for the elderly, and 310 mg for women aged 19-30 and 320 mg for the elderly elderly.

shortage

Magnesium deficiency

The low magnesium content in the plasma - called Hypomagnesemia - is quite common: it is found in 2.5-15% of the general population. From 2005 to 2006, 48% of the US population consumed less magnesium than recommended by the guidelines. Other causes of hypomagnesemia are: increased renal or fecal excretion, increased intracellular displacement and antacid therapy with proton pump inhibitors. Most cases of magnesium deficiency are asymptomatic, but symptoms may be related to anorexia, nausea, vomiting, neuromuscular dysfunction - increased excitability and cramps - cardiovascular dysfunction - arrhythmia, vasodilation - metabolic dysfunction and coma. Alcoholism is often associated with magnesium deficiency. Chronic low serum levels of the mineral are related to the metabolic syndrome, type 2 diabetes mellitus, fasciculation, arterial hypertension, some changes in hormone settings and some drug therapies.

deepening

Hypomagnesemia was found after prolonged activities with probable repercussions on performance due to the reduction in the protective action that magnesium exerts on the integrity of the muscle cell. It has been hypothesized that magnesium has an important action in promoting the release of oxygen to muscle cells during sports activities. This characteristic would be mediated by the ratio between the erythrocyte levels of magnesium and 2, 3 diphosphoglycerate.

The nutritional deficiency of magnesium and, more frequently, hypomagnesemia, determine: asthenia, cramps, tremors, apathy, muscle weakness and convulsions.

To learn more: Magnesium deficiency - magnesium supplements.

Toxicity

Magnesium toxicity

The increase in plasma magnesium or hypermagnesaemia is practically impossible to achieve with diet alone in conditions of perfect renal health. The odds increase by taking mega-doses of magnesium, which appears to have been attributed to the death of a child.

The most common symptoms of magnesium overdose are: nausea, vomiting and diarrhea. Hypermagnesemia, on the other hand, likely in those suffering from severe kidney pathologies that inhibit urinary excretion, causes a depression of the Central Nervous System (CNS) causing: hypotension, numbness and muscle weakness, prostration, cardiac activity disorders - arrhythmia - and respiratory, confusion, coma and cardiac arrest. This occurrence occurs especially when, in addition to decreasing the excretion of the mineral, the intake is increased - for example by certain drugs such as antacids or laxatives.

Read also: Magnesium: toxic when you least expect it.

Supplements

In some cases - especially in sports endurance and during the summer months - it may be necessary to use magnesium-based food supplementation. This requirement does not derive solely from the need to deal with an absolute type of deficiency - difficult to find - as regards the urgency of maintaining intra and extracellular electrolytic balances. For this reason magnesium should be taken together with other mineral salts, such as sodium and especially potassium - do you want to learn more? See also: Magnesium and potassium.

A specific magnesium supplement may also be useful in the treatment of pre-menstrual syndrome; for more information read also: Magnesium and premenstrual syndrome.

Among the magnesium salts most used for the integration we mention: Magnesium pidolate, Magnesium Chloride, Magnesium orotate, Magnesium oxide and Supreme Magnesium.

Numerous pharmaceutical preparations and food supplements based on magnesium are available on the market. In two human studies, magnesium oxide, one of the most widely used chemical forms - due to its high mineral content - was less bioavailable than citrate, chloride, lactate or magnesium aspartate. To learn more: Magnesium salts - Which one to choose?

Material

Magnesium as a material

Magnesium has a solid consistency, density equal to 2/3 of that of aluminum, lower melting and boiling point than all alkaline earth metals and glossy gray-white color. It closely resembles the other five elements of the second column - group 2 or alkaline earth metals - of the periodic table, with which it shares both the electronic configuration of the external electron and the crystalline structure.

It is the ninth most abundant element in the universe, the eighth most abundant in the earth's crust and the fourth on the entire planet - after iron, oxygen and silicon, which constitute 13% of the planet's mass and a large fraction of the outer mantle. It is the third most abundant element dissolved in sea water, after sodium and chlorine. Magnesium is found naturally only in combination with other elements and invariably at an oxidative state +2.

In free form - metallic - it can be artificially produced and is highly reactive - even if in the atmosphere it is quickly covered with a thin layer of oxide which partially inhibits its reactivity. The free metal burns with a characteristic bright white light.

Today the metal is mainly obtained by electrolysis of marine magnesium salts and is mainly used in combination with aluminum for the formation of special alloys characterized by lightness and strength.

Magnesium is the third most used structural metal, followed by iron and aluminum. The main applications of magnesium are, in this order: aluminum alloys, die-casting - in alloy with zinc - removal of sulfur in the production of iron and steel, and the production of titanium in the Kroll process.

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