Probiotics are live bacteria which exert their positive influence in a variety of ways. Laboratories all around the world are researching how probiotics interact with humans, and gradually scientists are building up a picture of which bacteria are the most effective in particular situations and how to get the best from them.
One of the ways that probiotics work is through competitive exclusion. This term was first coined by the brilliantly named Georgy Gause in the 1930’s. Gause was a Russian biologist who studied yeast and found that two similar but not identical populations of yeast would compete for the same nutrients in the same space. Even if everything else was equal, one population would eventually overtake the other and go on to crowd it out.
This is a phenomenon we can see in everyday life in any competitive system. Whenever two competitors fight over a finite resource, one will generally take the upper hand and gain control to the detriment or exclusion of the other.
It is the same with the bacteria living in the human gut. Of the 350 or more types of bacteria that make our digestive tract their home, less than 1% are potentially harmful or ‘pathogenic’. The majority either simply use the gut as their home or confer important benefits on the host, us, by helping our bodies absorb vitamins and other essential nutrients. The good bacteria crowd out the bad preventing them from gaining a foothold and growing to levels which would cause us harm.
This balance however is easily upset. A change in diet, infection, stress, or use of antibiotics can all shift this balance of bacteria, sometimes in favour of the pathogens. When this happens we experience the familiar symptoms of diarrhoea or constipation, bloating and discomfort. Drinking a healthy, live probiotic can redress the balance back in favour of the good bacteria by introducing a new, strong population of microbes which can overwhelm the ‘bad’ bacteria.
Probiotics which are alive and contain multiple strains are the logical choice since you want them to populate the gut quickly and have more than one bite of the cherry when it comes to competitive exclusion. The more strains the more chance of introducing one which will successfully populate the bowel and shift the balance back towards health.