When I was doing the copper detox, I took the taurine and had very dark BMs. But for some reason this was erratic and didn't always work; perhaps because of copper overload.
I am getting dark BMs again now by eating sauerkraut with every meal. Sauerkraut is loaded with b vitamins. I feel the sauerkraut makes a big difference for me. And it feels more 'natural' taking it, rather than taking taurine because it is a food.