Can having a bowel of All bran cause diarea. I hade a bowl of All Bran this morning with warm milk?

And my bowls have been open all day, and as I went to go for a run I had to come back in side quickly as when I went to to the toilet I had diarea, and had it again 2 minutes ago too. So does eating All Bran cause this? Any advice will do. I may have to cut back on the All bran becasue I do not want to be at a shopping centre and then run to find the closest toilet. Got any sugestions?