That looks like it, doesn't it Violeta? Vitamin B2 supps are absorbed in the small intestine (in the jejenum) and absorbed there without a problem but food with the precursors in it that are synthesised into Riboflavin may trigger these T-Cells in the colon. Maybe this is why people who end up with their colon removed don't get vitamin deficient, except perhaps B12 and vit K which are absorbed at the ileum - junction of small and large intestine. Meanwhile, been reading very interesting stuff about Riboflavin being produced by the bacteria b. subtilis in the colon. This is often in Kefir. I cannot take kefir although lots of IBD people can.