Contra-indications for Betaine HCL?

One of my problems I have been trying to address for years is that I'm really underweight.

I came across a post on CZ that supplementing with Betaine HCL has helped someone in a big way and so naturally i want to try it:)

Just wondering if it will be a problem, since HCL is acid. On the other hand, it's the same acid produced by our stomachs.

Which brings another interesting question. Does Miracle-Mineral-Supplement neutralize stomach acids???