title: Effects of dietary zinc levels, phytic acid and resistant starch on zinc bioavailability in rats.
abstract: BACKGROUND
  Owing to its fermentability, it has been advocated that resistant starch (RS) has a positive effect on the absorption of minerals by increasing their solubility in the hindgut. In marginally zinc-deficient rats, the enhancement of zinc bioavailability by RS occurs mostly when the diet contains phytic acid.
  
  
  OBJECTIVE
  This study aims to investigate the effect of dietary zinc level and phytic acid on the cecal zinc pools and zinc bioavailability of rats fed RS.
  
  
  METHODS
  Wistar rats (male, 3wk old) were divided into eight groups (n = 6), and fed diets containing either 5% cellulose (control fiber: insoluble and low fermentable) or 20 % RS (test fiber: soluble and fermentable), with or without the addition of 1% sodium phytate, at the 10 and 30 mg/kg dietary zinc levels, for 21 days.
  
  
  RESULTS
  At 10 mg Zn/kg, RS increased femur zinc concentration only in the group receiving the phytate-containing diet, while at 30 mg Zn/kg it increased femur zinc concentration in rats fed both phytate-free and phytate-containing diets. The total content of zinc in the cecum was increased by the higher dietary zinc level and tended to be increased by the addition of phytate, which is assumed to impair zinc absorption in the small intestine. Feeding RS lowered cecal pH values, which correlated with increasing values of zinc solubility (r = -0.3471; P < 0.05). The later was, in turn, directly associated with zinc apparent absorption (r = 0.3739; P < 0.05).
  
  
  CONCLUSIONS
  The increase in zinc bioavailability by RS occurs when dietary zinc levels are adequate and/or zinc absorption is impaired in the small intestine, increasing the influx of unabsorbed zinc into the cecum and favoring the increase of zinc bioavailability when RS fermentation lowers the cecal pH.
authors.affiliation: Dept. of Biochemistry and Food Science, Kagawa University, Kagawa, Japan. linayonekura@yahoo.co.jp
authors.forename: Lina
authors.initials: L
authors.lastname: Yonekura
authors.forename: Hiroo
authors.initials: H
authors.lastname: Suzuki
mesh_terms: D000818:Animals; D001682:Biological Availability; D002432:Cecum / Q000737:chemistry / Q000378:metabolism* / Q000382:microbiology; D004305:Dose-Response Relationship, Drug; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007408:Intestinal Absorption; D008297:Male; D010833:Phytic Acid / Q000494:pharmacology*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D012995:Solubility; D013213:Starch / Q000494:pharmacology*; D015430:Weight Gain; D015032:Zinc / Q000008:administration & dosage* / Q000172:deficiency / Q000493:pharmacokinetics*
chemical_list: D010833:Phytic Acid; D013213:Starch; D015032:Zinc