Studies have demonstrated over and over again that our digestive systems lack the same beneficial bacteria that our ancestors had-even just two generations ago. This is most likely due to changes in our diets and use of antibiotics.
In areas of the world (many studies have been conducted in Estonia and certain regions of Sweden) where children are not exposed to antibiotics, where families eat organic foods, and where diets consist largely of fermented foods (fermentation occurs via actions of "healthy" bacteria), children and adults still possess primarily "healthy" bacteria in their digestive tracts and there is a tremendous reduction in the incidence of allergic/inflammatory types of diseases.
Contrast the preceding paragraph with the situation in most of the western world. Our children are exposed to antibiotics numerous times during their first year of life, preventing them from acquiring the necessary healthy bacteria from birth. In fact, antibiotic exposure comes not only from antibiotic medications, but antibiotics are also detected in the meats that we eat. Additionally, we use antibiotic-soaps, antibiotic-detergents, antibiotic-hand cleansers, antibiotic-dish-washing liquids etc.
Unlike the foods that our grandparents grew up eating, our diets today consist largely of "foods-on-the-go" from "ready-to-eat" packages, rather than fermented foods (fermented milk products, fermented vegetables, etc.) When/if we DO eat fermented foods, these foods are often pasteurized before arriving in the supermarkets where we purchase them.
It has been documented that children who have been formula-fed as infants or who have been unfortunate enough to spend their early days in NICU (neonatal intensive care units) settings, possess atypical (abnormal and "unhealthy") bacteria living in their intestinal tracts.
In the western world, 1 out of every 3 children is diagnosed with an allergic/inflammatory disorder. Put all of these things together -- these changes in our diets and environments that have occurred over the past 60 years -- and it becomes obvious why it has become almost a dire necessity to "fix" our bodies.
The good news is: Probiotic bacteria can help.