looked at the bacterial profiles of stool samples rather than directly focusing on intestinal content this raised concerns that the conclusions drawn from prior studies may have been misguided however its important to remember that the new cell study was small and not designed to evaluate whether probiotics work overall the consensus is that we need further studies to more fully understand the effects of probiotics are they safe historically for healthy adults probiotics have been thought to be relatively safe when side effects do occur they tend to be mild digestive symptoms such as gas but in critically ill people or those with underlying medical problems such as compromised immune systems there have been reports of probiotics leading to severe side effects including dangerous infections one of the cell studies from this week found that when given after antibiotics probiotics delayed the community of bacteria in our guts known as the microbiome from returning back to its normal healthy preantibiotic state this raised concerns that probiotics may not be quite as harmless as we once thought even in healthy adults but we do not yet know how these findings translate clinically while the specifics with regard to the safety and efficacy of probiotics remains contentious something that is not controversial among scientists and health care providers alike is that the safest and most effective way to promote intestinal and immune health remains quite simply to eat a wellbalanced diet rich in vegetables dr nicky mehtani is an internal medicine physician at johns hopkins hospital and part of the abc news medical unit