A popular misconception is that probiotic microbes colonise the gut on a durable/permanent basis. This is simply not true. Probiotic microbes tend to persist in the gut for several days to a week. An exception to this can be bifidobacteria given in early infancy.

There is some limited evidence that these may become part of the gut flora in the infant on a longer-term basis. But for the overwhelming majority of people the persistence of supplemented probiotic microbes in the gut extends out to a maximum of about a week.

Most freeze-dried probiotic products have a seemingly impressive list of microbes listed on the label. The assertion is then made that the product is ‘multi-strain’. While this is true in a very limited sense, it is really sidestepping the whole reason why a consumer would want a multi-strain product in the first place.

 In the real world, microbes are never alone, they never live only among their own species/strain. Microbes are always in vast communities with friends and competitors engaged in an eternal struggle for survival. Very early in the development of probiotics, it was observed that cultures containing several different microbes tended to outperform cultures containing only a single strain. These observations were generally on live active cultures, not just blends of various powdered freeze-dried bacteria.

Myth #6:  All “probiotic” microbes are equal

There are a broad range of microbes touted as being “probiotic”. Lactobacilli and bifidobacteria are common in many ‘traditional’ probiotics, but one may find many novel products claiming to be probiotic with other types of microbes listed on the label.

Many processed foods now claim to be probiotic. These products are manufactured with spore forming (Bacillus) microbes. A Bacillus microbe can cease activity and form an endospore which are very tough and can endure certain manufacturing processes. The problem with spore-forming microbes is this very capacity to form a spore. When challenged, rather than fighting to the finish, they simply retreat into their spore form. This is not an option for ‘traditional’ probiotic microbes like lactobacilli.

Spore forming microbes also have a slightly higher risk than non-spore formers. In the very rare event that a probiotic microbe causes an infection (something that generally only happens in individuals who are severely immunocompromised) a spore-forming microbe can be harder to kill with pharmaceutical antibiotics than properly selected non-spore formers.