My DP is currently taking one of those vitamin supplements that make him like him but on a good day!
I am a bit of a skeptic when it comes to these sort of things and also have noticed that he is more agitatged than usual (he gets like this if he is drinking too much coffee too) so i had a look at the indredients and was 
Alot of the high level vits in this are B vitamins which i was aware that taking too many can have neurological effects. Also looked up some of the effect of overdose (ok so its pretty hard to overdose on vitamins but its not impossible, especially with long term use) and it was quite worrying.
Have asked him to stop taking them and you would have thought i'd asked him to give up heroin (so im gong to bloody hide the stuff or empty it out so that he runs out quickly and hope he doesn't buy more) I don't want to live with him being grouchy and short tempered because he is pumped up with too many vitamins and fecking guarana which apparently has more caffiene in than coffee 
Surely this is not healthy?