• Lena Frommelt, Maximilian Bielohuby, Barbara J M Stoehr, Dominik Menhofer, Martin Bidlingmaier, and Ellen Kienzle.
• Chair of Animal Nutrition and Dietetics, Ludwig-Maximilians University, Munich, Germany.
• Nutrition. 2014 Jul 1;30(7-8):869-75.

ObjectiveKetogenic 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).MethodsTwelve-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.ResultsThe 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.ConclusionThe alteration of apparent calcium and phosphorus digestibility may affect the impact of HFDs on bone metabolism.Copyright © 2014 Elsevier Inc. All rights reserved.

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