title: Effects of low-carbohydrate, high-fat diets on apparent digestibility of minerals and trace elements in rats.
abstract: OBJECTIVE
  Ketogenic low-carbohydrate, high-fat (LCHF) diets reduce growth and bone mineral density in children with epilepsy and in rats. Part of this effect might be due to a reduced availability of calcium in high-fat diets. The aim of this study was to determine mineral digestibility by total collection method in LCHF diets compared with a chow diet and a standard high-fat diet (HFD, high in fat and carbohydrates).
  
  
  METHODS
  Twelve-wk-old male Wistar rats were pair-fed isoenergetic amounts of either six different LCHF diets based on tallow and casein (crude fat 75%-50%, crude protein 10%-35%), with chow or with a HFD diet. Mineral-to-energy ratio was matched in all diets. Circulating parathyroid hormone was measured by immunoassay.
  
  
  RESULTS
  The apparent digestibility of calcium was reduced in all HFDs (high-fat diets, LCHF diets and the HFD diet) by at least 30% compared with the chow diet (P < 0.001). Fecal calcium excretion correlated positively with fecal fat excretion, presumably because of formation of calcium soaps. Apparent digestibility of phosphorous was higher in all HFDs. This resulted in a decrease of the ratio of apparently digested calcium to apparently digested phosphorous in all HFDs below a ratio of 1:1. Plasma parathyroid hormone was not affected by any diet.
  
  
  CONCLUSIONS
  The alteration of apparent calcium and phosphorus digestibility may affect the impact of HFDs on bone metabolism.
authors.affiliation: Chair of Animal Nutrition and Dietetics, Ludwig-Maximilians University, Munich, Germany.
authors.forename: Lena
authors.initials: L
authors.lastname: Frommelt
authors.affiliation: Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Klinikum der Universität, Ludwig-Maximilians University, Munich, Germany.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Bielohuby
authors.affiliation: Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Klinikum der Universität, Ludwig-Maximilians University, Munich, Germany.
authors.forename: Barbara J M
authors.initials: BJ
authors.lastname: Stoehr
authors.affiliation: Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Klinikum der Universität, Ludwig-Maximilians University, Munich, Germany.
authors.forename: Dominik
authors.initials: D
authors.lastname: Menhofer
authors.affiliation: Endocrine Research Unit, Medizinische Klinik und Poliklinik IV, Klinikum der Universität, Ludwig-Maximilians University, Munich, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Bidlingmaier
authors.affiliation: Chair of Animal Nutrition and Dietetics, Ludwig-Maximilians University, Munich, Germany. Electronic address: Kienzle@tiph.vetmed.uni-muenchen.de.
authors.forename: Ellen
authors.initials: E
authors.lastname: Kienzle
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002136:Calcium, Dietary / Q000378:metabolism; D004032:Diet; D050528:Diet, Carbohydrate-Restricted; D059305:Diet, High-Fat; D055423:Diet, Ketogenic; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage* / Q000378:metabolism / Q000494:pharmacology; D004063:Digestion; D008297:Male; D008903:Minerals / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism*; D016226:Phosphorus, Dietary / Q000378:metabolism; D017208:Rats, Wistar; D014131:Trace Elements / Q000378:metabolism*
chemical_list: D002136:Calcium, Dietary; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D008903:Minerals; D016226:Phosphorus, Dietary; D014131:Trace Elements; D010758:Phosphorus; D002118:Calcium
keywords: Apparent digestibility; Low-carbohydrate, high-fat diets; Minerals; Rats; Trace elements