Burnt Caramel

Source:  Burnt Caramel    Tag:  maple syrup urine disease facts
You're about to leave the path lab when the attending hands you a urine sample. "Smell this," she says.
"Are you out of your mind?" You almost ask. Instead, you say, "As you wish." After all, you really want that UCSF pathology residency.
The urine smells weird, almost like burnt caramel. "Diabetes?" you ask.
"Nope, it is pretty sweet smelling though. It came from a newborn. We need to put him on a special diet to prevent neurological damage."

Challenge: What restrictions will be put on the infant's diet? There are three specific things to avoid.

Related Questions:
1. What is this disease?
2. This disease has higher prevalence in those with a specific religion. What would this be?