Legumes can be a source of wheat contamination, but I assume that you use versions labelled "gluten-free."

You may want to look into Benfotiamine, which is the fat soluble version of B1.

Be sure all testing is completed before going gluten-free, that is, unless you are certain that gluten is the culprit and have decided not to eat it again. This article has some detailed information on how to be 100% gluten-free, so it may be helpful (be sure to also read the comments section.):    

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As a side note, it seems that medical science has evolved in the past 5-6 years regarding Celiac Disease, and I am now catching up. It seems that anything that disrupts the microbiome sufficiently enough can--in genetically susceptible individuals--lead to Celiac Disease. I have been reading now that antibiotics, excessive simple carbohydrates such as refined sugars and starches, the manner of birth such as C-section vs vaginal delivery, the diversity of one's diet, the presence of certain bacteria or viruses, can all contribute to microbiome dysbiosis, which can lead to Celiac. This is fascinating research.