The raw run form the tap in the tree is raw. Unfortunately it only contains about 1-3% sugars. It takes around 40 gallons of sap to make 1 gallon of maple syrup.
I think a better thing, and it's suggested in the Master-Cleanse book, is to use raw Sugar cane juice. But, having tried to before, that's easier said than done. Plus, here in the states, it's very expensive (when I've been able to find it).
I'm not sure if there is anything toxic about Maple Syrup or not but I understand that concern. Unfortunately, I'm underqualified to say whether it is or isn't.
Good luck, I look forward to reading what others say.