 This study is the first to investigate the relative colonisation of the human GI tract by L Reuteri ATCC PTA 4659. Simple demonstration that they survive passage is the first step in development of potential new probiotics, which is necessary before these strains can be considered for continued testing in probiotic food matrices. The aim of this study will evaluate the safety and tolerability of Lactobacillus Reuteri in healthy adult subjects. 