Magnesium transport in the gastrointestinal tract

Final evidence report as part of preparatory work for the setting of Dietary Reference Values for magnesium, copper and phosphorus

“…Absorption of magnesium is thought to take place in the small intestine, primarily in the distal jejunum and ileum with little absorption taking place in the colon (Kayne & Lee, 1993;Schweigel & Martens, 2000;Vormann, 2003), although some authors have expressed uncertainty about this (Coudray et al, 2003). Absorption takes place via two processes.…”

“…Firstly, paracellular absorption, which takes place via tight junctions and the intercellular space, is driven by electrochemical gradients and solvent drag (i.e. passive flux of water generated by non-magnesium solutes) and this is considered to be the dominant process (Schweigel & Martens, 2000;Coudray et al, 2003;Vormann, 2003). Only ionized magnesium is absorbed via the paracellular pathway (Quamme, 2008).…”

“…Secondly, transcellular absorption, which requires a transport protein to facilitate the passage of hydrophilic magnesium across lipophilic cell membranes and this mechanism is saturable, i.e. does not continue to increase at high levels of luminal magnesium concentrations (Schweigel & Martens, 2000;Vormann, 2003).…”

“…Intestinal absorption of magnesium is only loosely regulated and increases almost linearly with intake (Schweigel & Martens, 2000;Vormann, 2003) except at very low intakes where absorption is more efficient (Fine et al, 1991). The absorption of dietary magnesium varies between about 10-65% with the proportion of magnesium absorbed decreasing with increasing magnesium intake: Magnesium absorption is inhibited by intake of phytic acid (Brink & Beynen, 1992;Bohn et al, 2004) and phosphate (Bunce et al, 1965;Fine et al, 1991;Vormann, 2003).…”

Ioning Out the Diagnosis in Chronic Diarrhoea

“…6 Intestinal absorptive fractions of dietary magnesium vary from 30-60% depending on whether body stores are replete or depleted. 7 The main regulator of magnesium stores is the nephron, with the thick limb of the ascending loop of Henley controlling the proportion excreted or reabsorbed. Parathormone (PTH) sensitive magnesium channels control the reabsorption of filtered magnesium from the nephron.…”