The reduction and then complete elimination of symptoms was fairly quick. I would say in a few days at most. I did have some rumbling going on in my stomach also. I was not sure what this meant at the time and didn't really fuss too much about it as I was feeling better anyway. I would give it a shot if I was you, you have nothing to lose. Fermented foods are quite cheap and I wouldn't imagine that they would make you any worse than what you are now.
On another note, I don't really know why it has worked so well for me, and possibly not as well as for others (I presume this is the case as I have certainly put forward the case for fermented foods enough on this forum and so far no-one has come back with any positive results).