45I-15 |
Lactose and mannitol, but not glucose, increased calcium absorption in intact rats |
Y. ZHAO1, M. E. Wastney2, and C. M. Weaver1. (1) Dept. of Foods & Nutrition, Purdue Univ., 1264 Stone Hall, West Lafayette, IN 47907-1264, (2) Metabolic Modeling Services, Halmiton, New Zealand Lactose, glucose, and mannitol increase calcium absorption in intestinal loop studies. Glucose has been shown to increase water influx in the intestine and thereby, promote calcium absorption through solvent drag. In contrast, less absorbable lactose and mannitol induce the outflux of water to the lumen and potentially enhance calcium absorption through expanding tight junctions. Both lactose and mannitol influence calcium absorption most in the ileum. However, the effect of these carbohydrates on calcium absorption has not been studied in intact rats. This study was designed to use kinetic modeling to investigate the influence of lactose, glucose, and mannitol on calcium absorption in intact rats. After a week feeding of AIN 93G diet, 7-week-old Sprague-Dawley male rats were divided into 4 groups (n=8 rats/group) to receive test solutions by gavage containing either glucose (200mg), mannitol (200mg), lactose (400mg), or no sugar (control) plus 25 mg calcium in calcium acetate. Kinetic studies were performed. 1 or 2 rats from each group received 10 mCi 45Ca intravenously. 5 or 6 rats in each group were given 20 mCi 45Ca orally. A series of blood draws were taken right after dosing for 5 hours. WinSAAM was employed to estimate calcium absorption efficiency. There was no difference in calcium absorption between glucose treatment (40.57 ± 3.48 %) compared with the control ( 33.3 ± 4.9 %). However, lactose and mannitol significantly increased absorption efficiency of calcium by 50.8 ± 6.7 % and 70.4 ± 9.4 % respectively (P<0.001). Our results suggest that at same molar amount, only the carbohydrates that are less digested and absorbed, such as lactose and mannitol, increase calcium absorption. The enhancing effect is more likely to take place at lower part of small intestine.
Session 45I, Nutrition: General
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