Aspartame is a poison. Rather than taking a multivitamin you would be better to start juicing with organic green vegetables to detox your body and get real vitamins into your body. Many multivitamins are just synthetic copies of real vitamins and they contain minerals which are not organic so your body cannot assimilate them. Minerals in plants are organic and the body can use them. Wheatgrass, chlorella and spirulina are all excellent to detox your body as well.
Can I suggest you read Excitotoxins, the Taste that Kills by Dr. Blaylock, a neurosurgeon. MSG and Aspartame both kill brain cells. In his book he says that magnesium will protect you from the effects of MSG and aspartame (magnesium is found in green vegetables).
Another good author is Dr. Norman Walker who has some good books on juicing. He lived to about 109. Juicing is the fastest way to get nutrients back into the body. He also says that tap water is bad for us because it contains non organic minerals, again that the body cannot assimilate. We should all be drinking distilled water.