Low on B1- result of surgery or gluten free diet?

I am now on B1 supplements after my 6 month labs came back low. Do you think this is because we have been doing gluten free for several months or is it a side effect of the surgery? Coincidentally, since I started doing the gluten free stuff I have been losing much slower....I lost 14 pounds the last 12 weeks.

Google Gastrectomies. There is a Wiki description that talks about patients being low on B6 after having part of the stomach removed. I think this is something we will all have to be watchful of.