[The energetic utilization of L-fructose in rats]

The energetic utilization of L-fructose (LF) and D-fructose (DF) was investigated by means of indirect calorimetry in a difference trial on 9 male Wistar rats in the live weight range of 250 to 300 g. The daily rations in the two comparable periods with added fructose consisted of 10 g basal diet plus 2.7 g LF or 2.5 g DF. The digestibility and metabolizability of energy of the LF-ration were decreased by about 4 and 6%, resp., in comparison to the DF-ration. The efficiency of total utilization of energy (energy deposition/gross energy) amounted to (7 +/- 3)% (mean +/- SD) for the LF-ration and (10 +/- 3)% for the DF-ration. The lower digestibility of energy of the LF-ration was mainly due to a depression of apparent digestibility of crude protein, crude fat and crude fibre--obviously caused by increased microbial fermentation. With correction of the depression of digestibility the following values of energetic utilization resulted from the difference evaluation for LF and DF, resp.: digestibility (90 +/- 8)% and (100 +/- 6)%, metabolizability (85 +/- 8)% and (102 +/- 5)%, utilization of gross energy for energy deposition (69 +/- 11)% and (86 +/- 11)% and utilization of metabolizable energy (81 +/- 7)% and (84 +/- 11)%, resp.