Short- and long-term effects of probiotics administered early in life.

The concept of manipulating the gut microbiota through the administration of probiotics during early life in order to reduce the risk of and prevent or treat diseases, including those that manifest in later life, is appealing. However, a cautious approach is needed, and the long-term consequences of such administration should be carefully evaluated. Concerns related to the early administration of probiotics include timing, i.e. the administration often begins in early infancy, sometimes at birth, when gut microbiota is not fully established, and duration, i.e. the daily administration of such products is prolonged (several weeks or months). In the case of non-breastfed infants, delivery may be in the form of a specific matrix (infant formula) that could be the only source of feeding of an infant over a prolonged period. Finally, the fact that beneficial as well as some detrimental effects are seen years after administration of probiotics during the first months of life raises concern that other long-term effects such as immunosuppression in later life may also occur. Currently, while some promising data exist, there are still more questions than answers. However, rapid progress in this area of research is expected and no doubt will bring about a number of exciting findings.