G1inger - Phe is in most protein, so PKU sufferers have a low-protein diet (i.e. no meat, fish, dairy, eggs, etc & limited amounts of pasta, bread, certain vegetables). My DH is allowed 18g of protein a day - to put that in perspective, there's around 3g in the average slice of bread.
I think it might be that your DP has an allergy to actual aspartame, rather than the Phe which is only a part of it. Or he'd struggle on a 'normal' diet.
An aspartame allergy isn't unusual (my sister thinks she's allergic - she gets some digestive problems associated), and I think other sweeteners can do odd things to people who are sensitive too.
Avoiding aspartame (as opposed to Phe) should be quite straightforward to do with your LO, as you're already doing it for your DP at home.
If anyone's interested - here's some drinks that are aspartame free!
- Ocean spray cranberry squash (the half sugar ones have sucralose, normal are just sugar)
- tesco's standard lemonade is aspartame free! (beware, nearly all the big brand lemonades have aspartame in, including anything served in a pub)
- All the bottle green cordials are good
- 'full fat' coke is fine (obviously not any of the diet varieties).
And MmeLindt - you're right, it was shown that somewhere between the taste buds and the brain our bodies know when we're not getting actual sugar, and so you continue to crave the sugar. Normally, when you drink something containing glucose, the body releases stored glucose into the blood in anticipation - this doesn't happen if you've had sweetener instead (New Scientist article here)