I am confused about Truvia after reading the Fast Track book. The label says it’s erythritol, Reb a, and natural flavors. Isn’t erythritol ok(no FP)? I think the FP value of Truvia is 3, but does it have one at all? It’s my favorite sweetener and I would like to be able to use a little more in my coffee, but not at the cost of more heartburn.