Valerian has a sedative effect. Might help with your anxiety, but is more likely to just make you drowsy, depending on the dose. I have been taking it every night for years, along with melatonin, to help me sleep. Due to BPH (enlarged prostate), I would get up to go 2-3 times a night. The valerian/melatonin combo keeps that to one time, and makes it easier to get back to sleep when I do get up.
I take 1350 milligrams each evening. It has had no effect on my gut either way as far as I can tell.