Magnesium as a dietary supplement is offered in many forms including chelated, each being touted as being more absorbable by the body. I believe Mg has to be ionic to participate in biological functions and that any form is coverted to MgCl in the stomach, including chelated Mg. Does anyone know if this is true? Also if the chelated Mg is so stable, how can it be bioavailable?
Bill,
Magnesium is a divalent cation, and magnesium chloride is MgCl2. Stomach acid helps the dissociation of cationic magnesium. Magnesium chloride is absorbed much faster than magnesium sulfate, possibly owing to differences in the degree of dissociation between the two salts. Chloride is likely to be the most associated anion once dietary magnesium has entered the duodenum. The uptake (following equimolar administration) of the metal is the same whether it is administered as magnesium sulfate or chloride. It has been reported that the absorption of magnesium was higher when the associated anion was acetate. Greater intestinal absorption of the mineral occurs from stabilized low molecular weight amino acid chelates. Intestinal absorption of certain chelates has been reported to be several fold higher than that of magnesium sulfate.
Available magnesium supplements include magnesium chloride, magnesium citrate, magnesium oxide, magnesium gluconate and magnesium lactate, and various amino acid chelates, including magnesium aspartate. Salts of magnesium with a propensity to dissolve well in liquid exhibit more complete absorption in the gut than that obtained with than less soluble forms of magnesium. Studies have documented that citrate, aspartate, lactate, and chloride forms of magnesium show higher and more complete absorption and enhanced bioavailability than magnesium oxide and sulfate forms in humans . Magnesium oxide exhibits relatively poor bioavailability. In randomized double-blind clinical studies three preparations of magnesium (amino-acid chelate, citrate and oxide) were compared at a daily dose of 300 mg of elemental magnesium in 46 healthy individuals during a 60-day period; magnesium citrate was found to be more soluble and bioavailable than magnesium oxide, and a daily supplementation with magnesium citrate showed superior bioavailability after 60 days of treatment when compared with that of other treatments; chronic magnesium citrate supplementation yielded the highest mean salivary magnesium concentration in this study. Different anions bound to the cation, magnesium, such as oxide, chloride, gluconate and lactate, affect the delivery of the amounts of elemental magnesium to the target site, and consequently manifest divergent pharmacodynamic effects.
Inorganic magnesium salts, depending on the preparation, could have similar degree of bioavailability as organic magnesium salts. Presence of other minerals also influences magnesium absorption. For instance, Zinc, in very high doses from dietary supplements has been reported to interfere with magnesium absorption.
In 1833, Michael Faraday produced the metal, magnesium, by the electrolysis of magnesium chloride, which occurs both as anhydrous and multiple hydrated crystal forms. Absorption of magnesium from magnesium salts appears to be concentration dependent. It was reported to be most efficient from magnesium gluconate at 1 and 5 mM concentrations while at 10 mM concentration, absorption from magnesium fumarate was more efficient even though magnesium gluconate exhibited the highest bioavailability in rats using magnesium stable isotopes. Serum magnesium occurs as three fractions, either free/ ionized, bound to protein or complexed with different anions such as citrate, sulfate, phosphate or bicarbonate. Out of the three fractions in plasma, ionized magnesium exhibits the greatest biological activity. Absorption is complex, and is dependent on the individual’s magnesium status. Magnesium is predominantly absorbed in the distal intestine; absorption mainly occurs by intercellular diffusional mechanisms.
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