Magnesium is element that is closely related to calcium and strontium in the periodic table of elements. All three of these elements are interchangeable in bone because they have the same number of bonding sites for associated elements. Strontium though has no known role in biology in any species. Magnesium is the third most common element in bone behind calcium and phosphorus and the 7th most common in the body as a whole. It is a critical element in the body’s normal structure, metabolism, and neurologic function.

Pure Magnesium Atomic Number 12
Pure Magnesium Atomic Number 12From Wikipedia: Magnesium is the ninth most abundant element in the universe. It is produced in large, aging stars from the sequential addition of three helium nuclei to a carbon nucleus. When such stars explode as supernovas, much of the magnesium is expelled into the interstellar medium where it may recycle into new star systems. Magnesium is the eighth most abundant element in the Earth’s crust and the fourth most common element in the Earth (after iron, oxygen  and silicon), making up 13% of the planet’s mass and a large fraction of the planet’s mantle. It is the third most abundant element dissolved in seawater, after sodium and chlorine.

The important interaction between phosphate and magnesium ions makes magnesium essential to the basic nucleic acid chemistry of all cells of all known living organisms. More than 300 enzymes require magnesium ions for their catalytic action, including all enzymes using or synthesizing ATP and those that use other nucleotides to synthesize DNA and RNA. The ATP molecule is normally found in a chelate with a magnesium ion.

Dietary Sources of Magnesium for Bone Health
Spices, nuts, cereals, cocoa, and vegetables are rich sources of magnesium. Green leafy vegetables such as spinach are also rich in magnesium. The recommended daily intake for elemental magnesium is about 400 mg from all sources for adolescences and adults.

Magnesium Supplements
Numerous pharmaceutical preparations of magnesium and dietary supplements are available. Magnesium oxide capsules in amounts of 250 mg to 400 mg are available. Magnesium hydroxide (Milk of Magnesia) 15 ml or 3 tsp at bedtime provides a good source of magnesium and is a safe and effective way to promote regular bowel movements each morning.

Magnesium’s Employment in the Body’s Metabolic Economy
Adults have a total of about 24 grams of magnesium, with 60% in the skeleton, 39% intracellular (20% in skeletal muscle), and 1% extracellular. Serum levels are typically 1.8–2.4 mEq/L. Serum magnesium levels may be normal even when intracellular magnesium is deficient. The mechanisms for maintaining the magnesium level in the serum are:

  • Dietary intake
  • Gastrointestinal absorption
  • Renal excretion


Intracellular magnesium is correlated with intracellular potassium. Both low and high protein intake conditions inhibit magnesium absorption, as does the amount of phosphate, phytate, and fat in the gut. Unabsorbed dietary magnesium is excreted in feces; absorbed magnesium is excreted in urine and sweat.

Measuring Body Magnesium Stores is Challenging
Magnesium status is difficult to assess directly because most of this mineral is intracellular rather than in the extracellular space floating around in the blood stream. This makes relying on the serum magnesium alone deceptive. To support its metabolic needs for magnesium the body vigorously defends its serum level. When the serum magnesium is low, this means the whole body magnesium has been seriously depleted. Measuring erythrocyte magnesium concentrations coupled with the 24-hour urine magnesium excretion corrected for the 24-hour urinary creatinine excreting can finesse this measurement problem. Correcting the urine magnesium for the creatinine adjusts the total amount excreted for the patients lean body mass. People with greater lean body mass naturally have higher magnesium excretion due to the regular replacement of bone and muscle that occurs in all. Adjusting the calcium and magnesium for the patient’s creatinine corrects for the patient’s body size difference between patients and allows the clinician to make meaningful judgments regarding the adequacy or inadequacy of their dietary mineral absorption.

Magnesium Deficiency
Low plasma magnesium is common in the general population being present in between 2.5–15%. The primary cause is low dietary intake with only about 10% of US people getting 400 mg of magnesium from their daily diet. Alcoholism is another common reason for hypomagnesemia. Many alcoholics have poor diets, which contributes to the problem and alcohol may specifically enhance the excretion of magnesium. The loss of stomach acid with use of proton pump inhibitors and H2 blockers block magnesium absorption in the same way they interfere with calcium absorption. Magnesium needs stomach acid to ionize it properly to permit it to move through the cell membrane. Other causes are increased renal or gastrointestinal loss and increased intracellular shifts. Most people deficient in magnesium have no symptoms so it can go unnoticed for years before being detected.

Magnesium Overdose is Rare
Overdose from dietary sources alone never happens. It has happened when large doses of supplements are used but usually only in people with renal impairment. It is unlikely because not very much of oral magnesium supplement is absorbed and the excess magnesium in the blood is promptly filtered by the kidneys, and excreted in the urine. People with impaired renal function can absorb the magnesium but cannot excrete it. This causes them to become toxic on too much magnesium. .