Probiotics are beneficial live bacteria that naturally exist in our body, and they are particularly abundant in our gastrointestinal tract. In fact, there exist approximately trillions of bacteria belonging to 1,000 different species and composing of 5,000 strains in our digestive system
[2]. Everyone's gut has a unique population of bacteria that limit or support digestive functions. Variables that affect gastrointestinal microbiome include "age, diet, environment, genes, and medication"
[2][see also 6]. These factors may have negative or positive outcomes. For instance, some medications including antibiotics may impair gut microbiomes. A good or bad diet also creates a favorable or toxic ecosystem for bacteria in the body
[2]. Thus probiotics sourced from food and over-the-counter dietary supplements can be utilized to support a healthy gut and overall immune system
[2][4].