Yeah, this is why it maybe easier for people to get their B complex naturally (and far more effective I'd say too) from eating beef liver or taking dessicated liver tablets, OR taking nutritional yeast (not brewer's yeast).

I've had problems from B complex tablets too, so I dont usually stick to taking them. LIver however has been fine. And there is so much good in liver, that you get a lot of vitamins and minerals as well. but those who dont like eating it can take it in the tablet form.