My experience from back in the day when I was a daily megadoser of VitaminC - during normal time of feeling well, it took X amount of C to tip over the brink of bowel tolerance but during times of illness it took between 2X and 4X to produce the same "bowel flush" effect. It seems counter intuitive to me, and it took me years to connect these particular dots, but this is the way my body works.