Defending the barrier: Effects of probiotics on endogenous defense mechanisms

The 24th of January 2008 was the day that the BBC headlined: “Pancreatic deaths trouble Dutch” and the day that the field of probiotic research changed indefinitely. Probiotics, which had not shown any adverse effects in numerous conditions in the past, were for the first time associated with serious adverse events. In the largest study on probiotics to that date, the Dutch Acute Pancreatitis Study Group showed that probiotic treatment was associated with a more than twofold increase in death rate in patients with severe acute pancreatitis compared with placebo treatment. These results markedly intensified the debate about the place of probiotics as food supplements and their safety. While the mainstream media fueled fears of consumers, suggesting that their morning ritual may be lethal, scientists bombarded scientific editorial boards with letters criticizing the trial. And while nobody forgot to emphasize the previous successes yielded with probiotic treatment, the key question: “How is it possible that bacteria which are beneficial in less severe conditions seem to be lethal in these critically ill patients?” was not raised, let alone answered. In a quest to find the answer, this thesis hypothesizes that probiotics can be both friend and foe and that their effects rely on timing of administration and the patient’s condition.