Magnesium is the fourth most abundant mineral and the second most abundant intracellular divalent cation and has been recognized as a cofactor for metabolic reactions in the body. The average adult has 20-28 gm of magnesium, of which about 60% is in the bones. The rest of magnesium is in the muscles, soft tissues and body fluids. Magnesium in high concentrations can be found inside cells, especially heart and brain cells.

Physiological role of magnesium

Magnesium is a cofactor in over 300 enzymatic reactions, particularly those involved in the metabolism of food components and the creation of new molecules important for human health.

For all enzymatic reactions that require energy stored in molecules of adenosine triphosphate (ATP) is required magnesium. Mg²⁺ ion is trapped between the β-and γ-phosphate, thus reducing the strong anion exchange properties of ATP. In this way it can reversibly bind to proteins.

The synthesis of various molecules: Such molecules include proteins, nucleic acids, nucleotides, fatty acids and carbohydrates.

Activation of muscle concentration: Magnesium interacts with calcium in many body processes, such as regulation of blood vessels, contraction of muscles - including the heart muscle. Calcium stimulates contraction of muscles and blood vessels, while magnesium relaxes muscles and dilates blood vessels. Magnesium contributes to calcium balance in the body by acting on the hormones which control the absorption and calcium metabolism and interacts with the calcium transport mechanisms at the cellular level.

Ionic transport: Magnesium is involved in the maintenance of membrane electrical potential and the transport of sodium, potassium and calcium across the plasma membrane. Magnesium is involved in the transmission of nerve impulses.

Hormonal activity: Magnesium is necessary for the action of compounds that play a key role in the transfer of information from the hormones and other stimuli that cause chemical reactions within the cell. Magnesium increases the excretion of hormone insulin and contributes to a better entry into the cell. In this way, magnesium participates in the metabolism of carbohydrates.

Magnesium is also helpful in detoxification and bone ossification.

Metabolism

Although magnesium (and calcium) is present in many of natural food, body loses a large amount of it as in its processing. Mg²⁺ is reabsorbed along the small intestine, and the amount that is absorbed seems to depend primarily on the amount that reaches the intestine, and less than any other single factor, such as vitamin D. When the food has small amount of magnesium it can be reabsorbed up to three-quarters of Mg²⁺ from the food. Mg²⁺ reabsorption is not an active process, and there is no a common mechanism of calcium and magnesium transport in intestinal cells. In plasma, most of the Mg²⁺ is in a form that can be filtered in the renal glomeruli. Kidney, however, has an unusually high ability to retain Mg²⁺ in the body, so it is excreted about 1 mg of magnesium per day on a diet poor in this mineral. With a regular diet it is excreted about 35-45% of received magnesium in food in urine.

Magnesium is essential in the metabolism of thiamine, vitamin C and pyridoxine.

Magnesium is low absorbable if there are used a laxative at the same time and in the cases of infections and allergies.

Foods that are low in protein with and/or rich in phosphates may reduce the absorption of magnesium. Also, oxalates, which are found in some green plant foods, and phytates found in grainy foods produce insoluble complexes with magnesium and thereby prevent its absorption.

Larger amounts of zinc, calcium and vitamin D reduce the absorption of magnesium.

Food sources of magnesium

Although magnesium is a rather ubiquitous mineral, there is no major food that provides an extremely high amount of magnesium. Good sources of magnesium are whole (unrefined) grains, spinach, nuts, legumes, and potatoes (tubers), citrus and vegetables with dark green leaves (kale, broccoli) since magnesium is an ingredient of green pigment of plants - chlorophyll. The meat is also rich in magnesium, but also contains calcium, phosphorus and protein and reduce its absorption.

Refine of flour, polishing of grains, the extraction of sugar from molasses and other ways of preparing food almost completely removes magnesium.

Water is a good source of magnesium, especially in areas where is present "hard" water. Magnesium is usually better absorbed from the water than from food.

Other sources of magnesium are almonds, buckwheat, wheat bran, spinach, wheat germ, peanuts, unpolished rice, apricots, oatmeal.

Foods high in magnesium

Recommended daily allowance

Some researchers recommend a daily intake of magnesium of 6-10 milligrams per kg of body weight.

Magnesium deficiency

Symptoms of magnesium deficiency are irritability, personality changes, anorexia, body weakness, fatigue, dizziness, vertigo, insomnia, allergies, anxiety, convulsions (muscle spasms), the appearance of nervousness, tremor, twitching and messing tongue, involuntary eye movements, unsteady gait, abnormal heartbeat, low blood sugar levels and the occurrence of muscle contraction. In the absence of higher amounts of magnesium it also comes to hair loss, swollen gums and damage to the arteries that resemble atherosclerosis.

Magnesium deficiency is not rare and affects all body tissues. If the food has a lot of calcium, proteins and phosphate it will decrease the absorption of magnesium from the gut. To reduced absorption of magnesium may occur in cases of chronic diarrhea of any cause, poor diet in terms of protein and calories as well as in cases of severe inflammation in the body, difficult operations, disorders in the absorption of magnesium, hormonal disorders, cancer, pregnancy and in cases where the organism is under physical conditions. If someone suddenly stop hunger by providing proteins and carbohydrates without cofactors such as thiamine and Mg²⁺ it may result in metabolic and neurological disorders. In chronic renal failure, the need for magnesium is reduced, while in cases of renal acidosis and diabetes mellitus large losses of magnesium are caused. There are increased level of magnesium needed in women who are breastfeeding.

Intake of large amounts of phosphate, calcium, vitamin D, and saturated fatty acids also leads to a magnesium deficiency.

Magnesium deficiency is most common in people who eat canned food in large quantities, alcoholics and people who have problems with absorption. Also, this problem occurs in the elderly. Inadequate magnesium intake leads to the following disorders:

Cardiovascular disease including atherosclerosis, myocardial infarction, angina, ischemic heart disease, cardiac arrhythmias, and hypertension.

Diabetes: Magnesium deficiency leads to reduced insulin secretion and reduced tissue sensitivity to insulin. In diabetic women during pregnancy magnesium deficiency can significantly increase the risk of miscarriage or difficulties in childbirth.

Osteoporosis: Magnesium is important for the normal functioning of the bones. In addition, its role is in the functioning of the parathyroid glands, the metabolism of vitamin D and adequate sensitivity of bones to parathyroid hormone and vitamin D.

Migraine: Magnesium deficiency affects neurotransmitters, blood vessels and muscles of the head and neck.

Premenstrual syndrome: Changes the balance of calcium and magnesium due to hormonal fluctuations. It affects the levels of neurotransmitters and leads to premenstrual symptoms.

Asthma: Insufficient levels of magnesium in the body is associated with reduced lung function, bronchial hyperactivity and difficulty breathing.

HIV / AIDS: Magnesium deficiency has been observed in the initial stages of the appearance of HIV infection and leads to the appearance of fatigue, lethargy and mental weakness.

Lack of energy: People with magnesium deficiency during heavy physical exertion consume more energy than people who do not have a deficiency of this mineral.

Deficiency of magnesium also leads to acute kidney injury, kidney stones, gastric tumours.

Overdose

If renal function is normal there will not be toxicity with magnesium as the body ejects any excess of it. Severe symptomatic hypermagnesaemia is a rare clinical problem that predominantly results from excess exogenous magnesium intake in patients with renal failure. In the hypermagnesaemia the toxicity is manifested in depressive effects of magnesium on the nervous system.

Other symptoms of hypermagnesaemia include: Absent reflexes, respiratory paralysis, coma; Acute kidney injury; Bradycardia, hypotension; Cardiac arrest; Diarrhoea; Flushing of the skin; Hold your fluids in the body; Lethargy; Loss of reflexes; Low blood pressure; Nausea; Sedation, hyporeflexia, muscle weakness; Shallow breathing; Thirst; Vomiting; Weakness of the body.

Magnesium in medicine

Magnesium supplements are used to treat the following diseases and disorders:

Alcoholism; Angina; Asthma; Cardiac arrhythmias; Cardiomyopathy; Chronic fatigue syndrome; Diabetes; Disorders of internal organs; Epilepsy; Glaucoma; Hair loss; Heart attack; Hyperactivity disorder; Hypertension; Insomnia; Kidney stones; Migraines; Osteoporosis; Premenstrual syndrome; Problems with pregnancy and childbirth, preeclampsia, eclampsia.

References

Celi L.A., et al., 2013, “Association of hypermagnesemia and blood pressure in the critically ill,” Journal of Hypertension; 31(11): 2136-2141. [Web Reference]

Cheungpasitporn W., Thongprayoon C. and Erickson S.B., 2015, “Admission hypomagnesemia and hypermagnesemia increase the risk of acute kidney injury,” Renal failure; 37(7): 1175-1179. [Web Reference]

Elin R.J., 1994, “Magnesium: the fifth but forgotten electrolyte,” American Journal of Clinical Pathology; 102(5): 616-622. [Web Reference]

Freedman M.R. and Keast D.R., 2011, “White potatoes, including french fries, contribute shortfall nutrients to children's and adolescents' diets,” Nutrition Research; 31(4): 270-277. [Web Reference]

Freedman M.R. and Keast D.R., 2012, “Potatoes, including French fries, contribute key nutrients to diets of US adults: NHANES 2003-2006,” Journal of Nutritional Therapeutics; 1(1): 1-11. [Web Reference]

Kanbay M., et al., 2012, “Relationship between serum magnesium levels and cardiovascular events in chronic kidney disease patients,” American Journal of Nephrology; 36(3): 228-237. [Web Reference]

Paolisso G. and Barbagallo M., 1997, “Hypertension, diabetes mellitus, and insulin resistance: the role of intracellular magnesium,” American Journal of Hypertension; 10(3): 346-355. [Web Reference]

Reddi A.S., 2014, “Disorders of Magnesium: Hypermagnesemia,” Fluid, Electrolyte and Acid-Base Disorders. Springer New York. 285-288. [Web Reference]

Schelling J.R., 2000, “Fatal hypermagnesemia,” Clinical Nephrology; 53(1): 61-65. [Web Reference]

Soetan K.O., Olaiya C. O. and Oyewole O.E., 2010, “The importance of mineral elements for humans, domestic animals and plants-A review,” African Journal of Food Science; 4(5): 200-222. [Web Reference]

Takaya J., Higashino H. and Kobayashi Y., 2004, “Intracellular magnesium and insulin resistance,” Magnesium Research; 17(2): 126-136. [Web Reference]

Volpe S.L., 2013, “Magnesium in disease prevention and overall health,” Advances in Nutrition: An International Review Journal; 4(3): 378S-383S. [Web Reference]