title: Intestinal absorption of magnesium from food and supplements.
abstract: The purpose of this study was to measure magnesium absorption over the wide range of intakes to which the intestine may be exposed from food and/or magnesium-containing medications. Net magnesium absorption was measured in normal subjects after they ingested a standard meal supplemented with 0, 10, 20, 40, and 80 mEq of magnesium acetate. Although absorption increased with each increment in intake, fractional magnesium absorption fell progressively (from 65% at the lowest to 11% at the highest intake) so that absorption as a function of intake was curvilinear. This absorption-intake relationship was almost perfectly represented by an equation containing a hyperbolic function plus a linear function. Our results are statistically compatible with a magnesium absorption process that simultaneously uses a mechanism that reaches an absorptive maximum, plus a mechanism that endlessly absorbs a defined fraction (7%) of ingested magnesium. Compared to previous studies of calcium absorption, much less magnesium that calcium was absorbed at intakes above 8 mEq/meal, apparently due to greater restriction of intestinal permeability to magnesium. We also found that magnesium from a high magnesium-containing food source, almonds, was just as bioavailable as from soluble magnesium acetate. In contrast, magnesium absorption from commercially available enteric-coated magnesium chloride was much less than from magnesium acetate, suggesting that enteric coating can impair magnesium bioavailability.
authors.affiliation: Department of Internal Medicine, Baylor University Medical Center, Dallas, Texas 75246.
authors.forename: K D
authors.initials: KD
authors.lastname: Fine
authors.forename: C A
authors.initials: CA
authors.lastname: Santa Ana
authors.forename: J L
authors.initials: JL
authors.lastname: Porter
authors.forename: J S
authors.initials: JS
authors.lastname: Fordtran
mesh_terms: D000328:Adult; D002118:Calcium / Q000378:metabolism; D006801:Humans; D007408:Intestinal Absorption; D008274:Magnesium / Q000008:administration & dosage / Q000378:metabolism*; D008297:Male; D009754:Nuts; D010710:Phosphates / Q000378:metabolism; D012044:Regression Analysis
chemical_list: D010710:Phosphates; D008274:Magnesium; D002118:Calcium