The reason I ask this is because Edward had his own portal of truth that he discovers after leaving Gluttony, but that's the first time he notices it. The first time he meets Truth, there's only one gate. Unless that first gate was Edward's portal of truth, and Gluttony was like some weird second door that gave him a sort of secondary exit, wouldn't Ed still be able to perform alchemy?
We never really learn what the two different gates mean, other than that one is Edward's portal of truth. What is the other? Has it been there the whole time? (Is it the one he used when he was little? He performed alchemy then, didn't he? With just one portal of truth, that, for all we know, wasn't his? Is this making any sense?) He gives up his portal of truth, yes, and all that should do is make it so that Ed can't go hopping back and forth to see Truth, as that was the access the second portal kinda allowed.