Yes, for more than one reason. The resident microbiota of an individual is relatively fixed and thereby highly resistant to the establishment of “newcomers”. Even if L. reuteri is of human and naturally belongs in our bodies, the L. reuteri Protectis strain doesn’t colonize forever, especially not, when given after the age of three.
Even an indigenous bacterium like Lactobacillus reuteri should be taken on a regular basis, since most people of modern society does not get colonized by L. reuteri during infancy. The epithelial lining covers our gastrointestinal tract and works like a skin on the inside of our bodies. The main task of our ”inner skin” is to differentiate between what should be absorbed and what should not be let into our bodies. Biopsies have shown that Lactobacillus reuteri is temporarily binding to our epithelial lining. However, since the cells in our epithelial lining is replaced every fourth day, the majority of L. reuteri cells are also washed away within a week or so. Since L. reuteri colonization is transient, every day intake is recommended to ensure adequate and stable levels of L. reuteri in the gastrointestinal tract.
Read more about the epithelial lining – Gatekeepers in the gut