Cold Milk Accelerates Oro-Cecal Transit Time During the Luteal Phase but not the Follicular Phase in Women

The effect of the menstrual cycle on oro-cecal transit time (OCTT) has been controversial. Since poor reproducibility of OCTT measurements by lactulose might be responsible for this controversy, we measured OCTT with either milk or a solid test meal during the luteal and follicular phases of the menstrual cycle. Nine healthy young women (21.9 ± 0.42 years old) with regular menstruation were studied for 4 consecutive menstrual cycles. Control (37°C) or cold (10°C) milk was used as a liquid meal, and the OCTT measurements were taken 3 times at each milk temperature during each of the 2 phases for 3 consecutive menstrual cycles. OCTT after a solid test meal (cooked rice, miso soup, a boiled egg, and cooked soybeans with mixed vegetables) was studied twice in I menstrual cycle. Breath hydrogen was determined every 15 min for 6 h. OCTT was defined as the time when breath hydrogen showed a sustained rise of 3 ppm or more from baseline. OCTT was not different between the luteal and follicular phases when the test meal was control milk or the solid meal. When cold milk was used as the test meal, OCTT was significantly shorter during the luteal phase (134 ± 15 min) than during the follicular phase (165 ± 21 min). In conclusion, cold milk accelerates OCTT during the luteal phase but not the follicular phase of the menstrual cycle in women.