Magnesium is an alkaline earth metal and the fourth most common mineral in the human body. It occurs as the free cation, a positively charged ion, Mg2+ in aqueous solutions or as the mineral part of compounds, including chlorides, carbonates and hydroxides. In the body, approximately 60% of magnesium is stored in bones and 25% in muscle. The blood (serum) contains only 1% Magnesium.

Magnesium is mostly absorbed in the small intestine and is dependent on the amount ingested. Of the total dietary magnesium consumed, only about 24–76% is absorbed in the gut and the rest is eliminated in the faeces, as explained in this paper on Magnesium Basics.

Intestinal absorption is not directly proportional to magnesium intake but is dependent mainly on your magnesium status. In cases of lower magnesium levels, more is absorbed in the gut and, when you have higher magnesium levels, less is absorbed. Magnesium homeostasis is largely controlled by the kidneys.

Magnesium is an essential element required by the body as it takes part in over 300 enzymatic reactions and is necessary for the biochemical functioning of numerous metabolic pathways; such as protein synthesis, muscle contraction, blood glucose control, blood pressure regulation and nerve function. Magnesium is also crucial in the production of energy as it is a part of the Mg-ATPase complex and is essential for oxidative phosphorylation.

Scientists discovered ‘Magnesome’, a protein encoding gene incorporating Magnesium, suggesting that the levels of Magnesium in the body may epigenetically alter the expression and behaviour of some of the proteins in our bodies, so altering the expression of health or disease of tissues. These scientists concluded in the paper “The human “mangnesome”: detecting magnesium binding sites on human proteins” that “Presently we can annotate some 5% of the human genome as inheriting the capability of binding Magnesium ions.”  

Dietary sources of Magnesium include nuts, whole grains, such as brown rice and grain products, fish, seafood, several vegetables, legumes, and berries.

The modern diet contains calcium and magnesium in the ratio of between 5:1 and 15: 1 compared to the “cave man” diet of 1:1. Calcium and magnesium intakes can influence each other’s absorption. Too much calcium relative to magnesium can result in constipation. Magnesium is needed for smooth muscle contraction and excessive calcium can interfere with this. Excessive calcium can lead to kidney stones, arteriosclerosis, dementia, asthma and decreased glucose uptake.

The guidelines for Magnesium intake can be found in the Government Dietary Recommendations (2016) on the government’s website.

For adults (18+), the recommended daily intake for magnesium is 300 mg for men and 270 mg for women.

There is increasing evidence that nearly two-thirds of the population in the western world are not getting enough magnesium from their diet. It is this deficiency that is contributing to issues with many health conditions as described in the scientific paper, “The Importance of Magnesium in Clinical Healthcare”.

Why is there insufficient Magnesium in your diet?

Reduced Magnesium due to processing

Food processing is any method used to turn fresh foods into food products. The procedures used to do this can remove the portions of the plants that often have the highest magnesium content. For example, the process involved in refined grains removes >80% of the magnesium and refining sugar removes all of the Magnesium. The cooking and boiling of produce results in a significant decline of the food's Magnesium content.

Reduced Magnesium levels in soil

  • Some commonly used pesticides can bind and immobilise certain minerals, potentially decreasing the amount of magnesium in the soil and, therefore, also some crops, as discussed in this article on reduced nutrient concentrations in soybeans.
  • Potash, a commonly-used potassium fertiliser that’s easily taken up by plants, actually reduces the amount of magnesium absorbed by the plant.
  • The use of herbicides and pesticides also kill off worms and bacteria in the soil. The bacteria in the soil plays an important role in enabling plants to absorb essential minerals. Worms concentrate minerals in their castings in a form that is easy for plants to absorb. All of which is detailed in the research “The role of soil microorganisms in plant mineral nutrition”.
  • There has been increasing use of monoculture agricultural techniques, monoculture being the the agricultural method of producing or growing a single crop in the same place year after year. Whilst this has allowed increased efficiency in planting and harvesting, it increases the risk of exposure to diseases or pests so is not conducive to good soil health. Annually planting the same crop in the same area depletes the nutrients from the earth that the plant relies on and leaves soil weak and unable to support healthy growth.
  • With ever increasing heavy rainfall magnesium is one of the elements in soil that easily leaches.
  • Acid rain (from air pollution) contains nitric acid. In the soil Nitric Acid reacts with calcium and magnesium to neutralise excess nitric acid. Eventually, calcium and magnesium become depleted and the nitric acid reacts with aluminium oxide in the soil.  A reactive aluminium builds up replacing calcium and magnesium in the plant. As calcium is needed for cell wall strength and magnesium for chlorophyll for photosynthesis, plants may grow taller and faster but are weak and lack chlorophyll.

In simpler terms, it is our crop’s lack of magnesium and other nutrients that has such a direct impact on our ability to achieve sufficient magnesium through our diet.

crops nutrients soil

Reduced Magnesium levels due to lack of absorption/excess excretion by the body

  • Magnesium absorption is reduced in cases of vitamin D deficiency (prevalent in western diets) and altered in cases of certain gastrointestinal disorders for example; IBS, leaky gut, gluten and casein sensitivities, funguses and parasites.
  • Some medicines in common use, such as antacids, antibiotics, antihistamines, blood pressure drugs, diuretics and more can reduce magnesium levels, as outlined in this table of magnesium and drug interactions.
  • Alcohol is a magnesium diuretic, causing a marked increase in excretion of magnesium in the urine as detailed in this paper on magnesium deficiency and alcohol intake.
  • Caffeine also causes an increase in Magnesium excretions, as explored in the paper “Effects_of_caffeine_on_health_and_nutrition_A_Review”.
  • Smoking causes magnesium deficiency due to decreased supply from the diet (lesser appetite) and reduced absorption caused by disturbances in the digestive system functions, as shown in this study on levels of serum iron and magnesium in Sudanese cigarette smokers.
  • Magnesium deficiencies are often seen in the elderly due to reduced intestinal absorption, reduced stores in the bone and excess loss in the urine, this is explored in detail in the paper “Magnesium homeostasis and aging”.
  • Some foods can block the absorption of magnesium, for example, high protein diets can decrease magnesium absorption. Tannins in tea bind and remove minerals including magnesium. Oxalic acid in rhubarb, spinach and chard and phytic acid in cereals and soy also block the absorption of magnesium.
  • Saturated and trans fats alter cell wall integrity, making it more rigid, which affects receptor site function and prevents nutrients from getting into or out of the cell.
  • Increased levels of stress can result in decreased levels of hydrochloric acid in the stomach, which results in decreased absorption of magnesium.
  • Fluoride in water and toothpastes, can interfere with the absorption of magnesium in the gut, as fluoride ions (F-) have a high affinity for magnesium. This is shown in the paper “Fluoride – Magnesium interaction”.

Magnesium Contributes to the Following Beneficial Physiological Effects

Note: These EU health claims apply where a food is at least a source of magnesium as per Annex to Regulation (EC) No 1924/2006. Such amounts can be easily consumed as part of a balanced diet. The target population is the general population.  

Magnesium contributes to Electrolyte balance

Electrolytes are minerals in the body that have an electrical charge. Calcium, magnesium, sodium, potassium, chlorine and phosphate are all electrolytes. Levels of electrolytes can become too low due to sweating, vomiting, diarrhoea or even over hydration. The balance of the electrolytes is critical for the normal function of cells and organs.

Magnesium functions as a cofactor of many enzymes involved in the maintenance of the electrical potential of nerve tissue and cell membranes. Deficiency of magnesium can impair the sodium potassium ATPase pump as well as calcium-blocking activity leading to membrane destabilisation and hyperexcitability (Magnesium: Clinical considerations, E L Tso and R A Barish. 1992).

condensation sweat electrolytes

Magnesium contributes to normal energy yielding metabolism

Cellular respiration involves many chemical reactions that ultimately result in the production of chemical energy in the form of ATP (Adenosine Triphosphate). The three stages of this are Glycolysis (glucose splitting), Krebs Cycle and finally Electron Transport where energy from NADH and FADH2, which result from the Krebs cycle, is transferred to ATP. Magnesium has a predominant role in the production and use of ATP, as it forms Mg-ATP complexes. These complexes are cofactors for several kinases, which are enzymes that add phosphate groups to other molecules, that are active during glycolysis, the process that converts glucose into two three-carbon compounds producing energy. Magnesium also regulates the activity of several enzymes involved in the Krebs cycle.

Magnesium contributes to normal neurotransmission

Magnesium affects a number of neurotransmitter systems, as covered in the paper Magnesium and Stress by Magdalena D. Cuciureanu and Robert Vink. It acts as a calcium channel blocker and calcium metabolism regulator. It counteracts calcium at NDMA (glutamate) receptors. Activation of NDMA receptors results in the opening of an ion channel; Magnesium ions block the ion channel allowing the flow of sodium ions and small amounts of calcium ions into the cell and potassium out of the cell. Calcium flux is critical to synaptic plasticity, a cellular mechanism for memory and learning.

Low levels of magnesium result in hyperexcitability of the nerves and random firing. This can alter sleep patterns making it difficult to get to sleep.

Researchers Starobrat-Hermelin & Kozielec have shown in the 2004 Assessment of magnesium levels in children with ADHD (Attention Deficit Hyperactivity Disorder) that an improvement in hyperactivity can be seen with supplemental Magnesium.

Further research byHuss, Völp and Stauss-Grabo, 2010 found these benefits were enhanced further when supplementing with Omega 3 fatty acids.

Magnesium contributes to the maintenance of normal muscle contraction

Magnesium contributes to normal muscle contraction including normal heartbeat. Magnesium acts as a natural calcium blocker helping your muscles relax. Calcium itself binds to specific proteins, changing their shape and causing the muscle to contract. Magnesium competes with calcium to reach these binding sites and so causes the muscles to relax. Without sufficient magnesium competing with calcium the muscle may contract too much, causing cramps. The same occurs in the heart muscle where the natural competing of magnesium and calcium bringing about a healthy heartbeat. When magnesium levels are low, calcium may overstimulate the heart muscle cells causing a rapid or irregular heartbeat.

Studies at the University of Texas have shown that deficiency of magnesium results in cramping and severe muscular pain such as that which occurs in Fibromyalgia. When Magnesium malate was clinically demonstrated to improve pain and tenderness when it was administered to patients with fibromyalgia.

More recent studies, such as this magnesium study published in Rheumatology International, have evaluated the use of magnesium citrate, instead of magnesium malate, to ease pain in fibromyalgia patients.

Low levels of magnesium in the blood are also related to various cardiovascular conditions, as explored in this paper on Hypomagnesemia and cardiovascular system

Magnesium contributes to normal cell division

Magnesium is involved in many stages of eukaryotes cell proliferation. This includes initiation, DNA replication and, as shown in this paper on the effects of magnesium, the formation of the mitotic spindle.

Studies, such as this on magnesium deficiency and its effect on mammary epithelial cell proliferation, have shown that low magnesium levels are associated with increased oxidative stress and decreased cell proliferation.

Magnesium deficiency (known as Hypomagnesemia defined by low serum magnesium levels) is common in 13.5% and 47.7% of type 2 diabetes individuals. Magnesium has demonstrated involvement in the improvement of beta cell function in a double-blind randomised study on magnesium and beta-cell function in no-diabetic individuals, it was concluded that magnesium chloride improves the ability of beta cells to compensate for variations in insulin sensitivity.

Magnesium contributes to the maintenance of normal bone & teeth

60% of the body’s Magnesium is found in bone. Magnesium is needed for the absorption, transportation and metabolism of calcium, regulating the parathyroid hormone that regulates bone breakdown and activating the enzyme required for the production of new bone. A study of trabecular bone density of peroral magnesium in osteoporosis showed that Magnesium can improve bone density.

Low levels of Magnesium in the blood and a low Magnesium:Calcium ratio have been associated with an increased risk of periodontal disease and poor tooth integrity, as illustrated in this paper, “Magnesium deficiency is associated with periodontal disease”.

teeth bones xray

Magnesium contributes to normal protein synthesis.

Magnesium is required for the synthesis of nucleic acids (the building blocks of proteins). Magnesium is required during DNA, RNA and protein synthesis.

Magnesium is also required for the synthesis of glutathione, a powerful cellular antioxidant.

Magnesium contributes to a reduction of tiredness and fatigue

Due to magnesium’s role in every cell in your body, any decline in magnesium status is often associated with symptoms such as tiredness and fatigue.

Magnesium contributes to normal psychological function

There is a lot of research evaluating the role Magnesium has to play in neurological conditions.

Magnesium plays a major role in relaying signals between your brain and your body. It binds to specific sites on NMDA receptors, which play a unique role in synaptic function, as further clarified in the paper “Influence of External Magnesium Ions on the NMDA Receptor Channel Block by Different Types of Organic Cations”.

The role of magnesium in mental performance (where mental performance stands for those aspects of brain and nerve functions that determine aspects like concentration, learning, memory and reasoning) and “brain function” is becoming more and more evident.

A decline in magnesium status is associated with various symptoms such as depression, psychosis, irritability or confusion.

Depression has been demonstrated in people with low red blood cell Magnesium levels, as illustrated in this magnesium study by Mihai Nechifor

Another study by A. A. Spasov on magnesium deficiency, showed that anxiety and depressive-like symptoms surface if Magnesium is removed from the diet..

One particular review, titled “Magnesium for Treatment-Resistant Depression”, noted correlation between increased rates of depression and reduction in the diet of magnesium.

Magnesium contributes to normal hormonal health

Magnesium is an essential co-factor in fatty acid metabolism that impacts upon hormonal health.

Magnesium and Gut Health

Our gut microbiome is very important to overall physical and mental health. It is comprised of trillions of micro-organisms (bacteria, viruses, fungi etc)-some pathogenic, some beneficial present in the digestive system. The gut microbiome affects the body by controlling the digestion of food, immune system, central nervous system and various other bodily processes.

There is a lot of current research, such as this paper published by the American College of Rheumatology, regarding magnesium and how deficiency affects the gut microbiome, imbalances of which can lead to various health implications.

In one 2010 magnesium study, nutritional modulation of Magnesium was suggested to decrease bifidobacterial content, increasing the permeability of the intestinal wall resulting in inflammation.

What are the Symptoms of Magnesium Deficiency?

Magnesium deficiency, also known as ‘Hypomagnesemia’, can be hard to diagnose. Assessing magnesium status is difficult as most magnesium resides inside cells or bones. The most common method for measuring your magnesium status is by measuring the serum magnesium levels, even though this has little correlation with total body magnesium levels or concentrations found in specific tissues. The following signs could indicate you are deficient in magnesium:

Mild symptoms



Decreased appetite


Unable to think clearly

Fatigue and muscle weakness


More severe symptoms


Muscle twitches and cramps

Mental disorders


Abnormal heart rhythms

It should be noted that, with Hypomagnesemia, there is an increased excretion of potassium by the kidneys, resulting in a condition known as hypokalaemia (low potassium). Symptoms of this can include weakness, fatigue, constipation, muscle cramping, palpitations and, in more severe cases paralysis, and respiratory failure.

How to Get Enough Magnesium

Eating magnesium-rich foods found in both plant and animal sources such as seeds and nuts along with whole grains, beans and leafy green vegetables is one way of obtaining magnesium. For reasons discussed earlier, obtaining sufficient magnesium from food sources and diet alone may not always be achievable, particularly if you are showing signs of severe magnesium depletion.

It is generally accepted, and referred to in many articles such as this on "Magnesium metabolism and perturbations in the elderly",that magnesium requirements increase in the elderly. Data published by the WHO (The World Health Organization )in 2011, shows that older adults will soon form the single largest demographic group, with more older people than children; the health consequences of this are continually under discussion, as illustrated in the research “The Importance of Magnesium in Clinical Healthcare”.

Supplementation with magnesium supplements in order to support your magnesium requirements is  one way of adequately achieving your necessary daily intake.

food nutrients

Bioavailability Of Different Magnesium Supplements

Because magnesium is a very chemically active metallic element, it occurs naturally only in combination with other elements. magnesium supplements are usually a combination of magnesium with another substance such as a salt or, in case of magnesium bisglycinate, a chelated magnesium (a chelated mineral is one that is bonded to another molecule, typically amino acids). They occur as organic and inorganic magnesium salts. Each combination with magnesium provides different amounts of elemental magnesium. The amount of magnesium and its bioavailability determine the effectiveness of the supplement.

Bioavailability refers to how easily a substance is absorbed by the body and refers to the proportion of the administered substance capable of being absorbed along with that available for cellular uptake, use or storage. In short, the amount of magnesium that your tissues can use readily is based on how soluble the magnesium product is and the amount of elemental magnesium that is released. Another factor that affects the absorption of magnesium is the existing magnesium levels of the individual, as magnesium will be less rapidly absorbed if body levels are already adequate and excreted through the urine or stools if given in excess.

The extent of water solubility of magnesium compounds plays a part in magnesium’s availability and oral absorption. Those forms that dissolve well in liquid are more completely absorbed in the gut than less soluble forms. Organic magnesium salts are, in general, more soluble than inorganic magnesium salts.

Organic magnesium salts

Magnesium Citrate

Magnesium citrate is a form of magnesium bound to citric acid, an acid found naturally in citrus fruits giving them a tart, sour flavour. Some research, such as this clinical trial on the bioavailability of different forms of magnesium, indicates this is one of the most bioavailable forms of magnesium.

Magnesium citrate works by increasing the water in the colon through the colon’s tissues by a process known as osmosis. When the magnesium citrate reaches the small intestine, it attracts enough water to induce defecation. The extra water helps create more faeces, stimulating bowel motility and, therefore, may have a mild laxative effect. This form of magnesium functions best on an empty stomach followed by a full glass of water or juice to aid absorption.

Researchers have demonstrated that magnesium bioavailability is greater in citrate than oxide, taking the pH of stomach acid and alkalinity of pancreas into consideration.

Magnesium Malate

Magnesium Malate includes malic acid, an organic compound (often called ‘fruit acid’) found in many fruits including apricots, grapes, and pears; and is responsible for giving them a tart taste. The weak ionic bonds of magnesium and malic acid are easily broken, making it readily soluble in the body and therefore well absorbed. Some people report that magnesium malate is gentler on your system and may have less of a laxative effect than some other magnesium supplements.

Magnesium Ascorbate

Magnesium Ascorbate is a buffered (non- acidic) form of vitamin C and magnesium. It is a neutral salt that has a significantly higher gastrointestinal tolerance than some of the other forms. It offers a source of both magnesium and vitamin C with good bioavailability.

Inorganic magnesium salts

Magnesium oxide

This is a salt that combines magnesium and oxygen. It has the highest elemental Magnesium (60%), but it has a low solubility and is therefore poorly bioavailable. Gut absorption is believed to be as low as 4%.

You will find that magnesium oxide is very common in poor quality supplements simply because it is cheap, however, only about 4% of its elemental magnesium is absorbed, equivalent to about 12 mg out of a 500 mg tablet.

Magnesium Chloride

Magnesium chloride, as in Metabolics Ionic Magnesium and Ionic Magnesium XS, is a magnesium salt that includes chlorine. It is completely ionized across a large pH range, 2 (found in stomach acid) to 7.4 (found in extracellular tissues such as blood and lymph) and is well absorbed in your digestive tract. Magnesium chloride has the chloride part of its compound to produce hydrochloric acid in the stomach and enhance its absorption. This is particularly suitable for anybody with low stomach acid (production of stomach HCl is known to decline with age).

Magnesium Sulfate (or sulphate)

Magnesium sulfate is also known as Epsom salts. It contains magnesium; sulphur and oxygen.  It is the main preparation of intravenous magnesium. Bioavailability is limited and variable with degrees of mild diarrhoea, as shown in this research article on the absorption of magnesium from orally administered magnesium sulfate. It is often used as a treatment for constipation.  

Magnesium Phosphate

Magnesium Phosphate is practically insoluble in water. Magnesium is bound to phosphate in teeth and bone.

Magnesium Carbonate

Magnesium Carbonate is nearly insoluble, however, in the presence of stomach acid (HCl) it is converted to magnesium chloride. In large doses this form may have a mild laxative effect.

Magnesium Hydroxide

Magnesium hydroxide has a relatively high percentage of elemental magnesium but has a low solubility in water, suggesting poor absorption. When in a suspension in water, it is often called milk of magnesia, used as an antacid or laxative. Although it has a high percentage of elemental magnesium, the magnesium ion is very poorly absorbed from the intestinal tract, drawing water from the surrounding tissues by osmosis.

Chelated supplements

Magnesium Bisglycinate is a chelated form of magnesium and the amino acid glycine. The presence of glycine has a buffering effect on the chelated magnesium, which improves the solubility of the whole compound and, therefore, improves its bioavailability. Due to the presence of glycine, this form also has a calming effect on your brain and has been reported, as evidenced in this paper on “New Therapeutic Strategy for Amino Acid Medicine”, to improve sleep quality. 


Absorption of magnesium is a complex process, which has a major impact on the relative bioavailability of supplements. All are suitable for restoring magnesium status under normal physiological conditions, it is a case of establishing which one is right for you and consulting your healthcare practitioner and conducting research into intestinal absorption and factors influencing the bioavailability of magnesium. Although magnesium supplements are generally considered safe, you should check with your healthcare practitioner before taking them — especially if you have a medical condition. High doses of magnesium can result in diarrhoea.


Metabolics Magnesium Supplements

Capsule forms

Product Name

Elemental Magnesium Per Capsule

Magnesium Ascorbate

61 mg (along with 467 mg as Vitamin C)

Magnesium Bisglycinate

133 mg

Magnesium Carbonate

117.5 mg

Magnesium Citrate

73 mg

Magnesium Cit/Mal

71 mg

Magnesium Hydroxide

144 mg

Magnesium Malate

63 mg

Magnesium Phosphate

99 mg

Magnesium Sulfate

104 mg

Calcium Magnesium Cit/Mal

51 mg  (along with 50 mg as Calcium)

Vitamin C Buffered

73 mg  (along with 349 mg as Vitamin C, 14.4 mg as Zinc & 13.5 mg as Potassium)

Liquid forms

Product Name

Elemental Magnesium Per Serving

Ionic Magnesium

 1.7 mg in 10 drops from Magnesium Chloride

Ionic Magnesium XS

10.6 mg in 10 drops from Magnesium Chloride