If a bacterial strain wants to be defined a probiotic and be used as a food supplement, it must be studied in deep to assess whether it possesses or not some peculiar characteristics.
First, it must be identified taxonomically, knowing its “name and family name”, by studying its DNA (we want to know who we are dealing with!).
Moreover, it must be stable: it must maintain its “superpowers”, passing undisturbed through the stomach to reach the final destination of its journey, the intestine.
It must also be active because, once reached the gut, it must be able to find its place, adhere to the intestinal mucosa and colonize it, multiplying and thus creating its progeny.
It must be effective it must be able to perform its specific function. Indeed, each probiotic strain has a special task to accomplish that distinguishes it from the others. These functions are analyzed in detail in the pre-marketing phase, granted by an evaluation performed by the European Food Safety Authority (EFSA). What is remarkable is that the effects exerted by the probiotics, in addition to the gut, are then able to propagate specifically to other anatomical sites even far away, such as the skin or the brain.
Moreover, the probiotic must also be assumed in a proper dose (the right quantity), identified as at least 1 billion live cells per day.
Last but not least, it must be safe, meaning that it must not lead to adverse side effects on our bodies. Many studies are carried out first in the laboratories (in vitro tests), such as on antibiotic resistance, and then through clinical trials (in vivo tests), to ensure the safety of the strain.
Once the probiotic candidate has passed all these checks, it is ready to be formulated and placed on the market.