It won't make a difference unless you let it. The amount of carbohydrates is no more than a glass of lemonade. When this has come up before I usually advise people to allow the wafer to dissolve in the mouths and allow the enzymes to get to work, also hold the juice in the mouth for a little while. This is also good because you can concentrate on the meaning of the bread and wine and allow them to become part of you. I believe the spiritual significance of Communion is more important than the cleanse, but to set your mind at ease it will not hurt you.