I haven't firmly made up my mind about vitamins. My shipment from Atkins didn't arrive until well after the first week so I did that without any supplements of any kind. Seemed to do fine. Now I'm taking the three main ones that Atkins recommends (at least half of the recommended amount each day) and don't notice anything that I could possibly ascribe to them. But that doesn't mean that I don't need them or that they are not having a positive effect.