In well-fed young rats, lactose-induced chronic diarrhea reduces the apparent absorption of vitamins A and E and affects preferentially vitamin E status.

To establish the effect of lactose-induced diarrhea on the apparent absorption and status of vitamins-A and E in well-fed young rats, we fed Sprague Dawley rats a balanced diet or a lactose diet (350 g/kg). A group of rats fed the control diet equal to the level measured in the lactose-fed rats (pair-fed) was also included. The experiment lasted 23 d and feces were collected on days 4-6, 10-12, 14-16 and 20-22. Samples of serum and tissues were taken on days 10 and 23. Lactose caused a significant reduction in food intake, had no effect on body weight and produced a diarrhea that persisted during the whole experiment. The severity of diarrhea decreased with time, indicating that the rats partially adapted to lactose feeding. At the onset of diarrhea, the apparent absorption of vitamins A and E in the rats with diarrhea was significantly lower than in the control or pair-fed rats, but the rats with diarrhea recovered gradually, and in the case of vitamin E was normalized by day 15. At day 10 the rats with lactose-induced diarrhea had serum and liver concentrations of vitamins A and E that did not differ from the control or pair-fed rats. However, at day 23 the lactose-fed rats with diarrhea had significantly lower serum and liver concentrations of vitamin E than the control or pair-fed rats. Measured at that time, diarrhea had no effect on liver vitamin A, but lower serum concentrations of this vitamin were detected in both the lactose-fed rats and in the pair-fed rats. In general, in well-nourished rats, the chronic diarrhea associated with excessive dietary lactose reduced the apparent absorption of vitamin A and E and particularly compromised the nutritional status of vitamin E.