title: Magnesium and calcium absorption in Fischer-344 rats influenced by changes in dietary fibre (wheat bran), fat and calcium.
abstract: Magnesium and calcium absorption were affected by changes in dietary wheat bran fibre and calcium, but not fat, in Fischer-344 rats when studied in a full factorial study which was a portion of a larger study of diet and colon carcinogenesis. For four weeks, nine-week-old rats were fed experimental purified diets to which had been added: wheat bran 0, 2.5 10, or 20%; fat 1, 5 or 10%; and calcium 0.18, 0.52, or 1.04% of diet weight. From day 26 to 29 all faeces were collected in metabolic cages, and food consumption noted. Dietary magnesium intake and net magnesium absorption increased in direct relation to the quantity of wheat bran in the diet. Calcium supplementation inhibited magnesium absorption on fibre-free diet, but had little effect on magnesium absorption when fibre was present. Fat had no measurable effect on magnesium absorption. A low dietary fibre content enhanced Ca absorption compared to that on a fibre-free diet. However, further increases in fibre content slightly inhibited calcium absorption. We conclude that the magnesium content of dietary wheat bran fibre is available for absorption to rats. Calcium supplementation inhibits magnesium absorption in a fibre-free diet, but presence of dietary fibre protects magnesium absorption from the calcium inhibition observed on a fibre-free diet. Absorption of calcium is increased by including some fibre in the diet. However, calcium absorption may be diminished slightly by increasing wheat bran content of the diet to a high level, probably through calcium binding and excretion with undigested fibre.
authors.affiliation: Institute for Disease Prevention, George Washington University Medical Center, Washington DC.
authors.forename: D W
authors.initials: DW
authors.lastname: Watkins
authors.forename: S
authors.initials: S
authors.lastname: Jahangeer
authors.forename: M K
authors.initials: MK
authors.lastname: Floor
authors.forename: O
authors.initials: O
authors.lastname: Alabaster
mesh_terms: D000818:Animals; D001682:Biological Availability; D002136:Calcium, Dietary / Q000493:pharmacokinetics* / Q000494:pharmacology*; D004041:Dietary Fats / Q000494:pharmacology*; D004043:Dietary Fiber / Q000008:administration & dosage / Q000494:pharmacology*; D005243:Feces / Q000737:chemistry; D007408:Intestinal Absorption / Q000187:drug effects*; D008274:Magnesium / Q000493:pharmacokinetics*; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344 / Q000378:metabolism
chemical_list: D002136:Calcium, Dietary; D004041:Dietary Fats; D004043:Dietary Fiber; D008274:Magnesium