Arsenic undergoes significant speciation changes upon incubation of contaminated rice with human colon micro biota

► Postulates pre-systemic arsenic metabolism, even when it is bound in a rice matrix. ► Effect of different matrix of rice on As bio-accessibility at colon level. ► Depending upon content of rice, the most bio-accessible species are differing. ► Depending upon content of rice, pattern of bio-transformations is changing.