This is why some people who try nutritional approaches to managing this situation often meet with mixed results. The main reason that people have poor digestion is the use of antibiotics. It does not matter what the anti-biotic is or where it comes from. Doctor-prescribed antibiotics, chlorine in the water and preservatives in food are all antibiotics and very destructive to the body. They are supposed to continue to reproduce there throughout our lives.
Antibiotics kill the good bacteria.
The body needs to be able to eliminate wastes. When the intestines become clogged and infested, they turn from becoming good waste removers into being waste generators. The body now has a self-poisoning system built right into it. On top of the poisons that the bad bacteria, yeast, mold and parasites are putting out, we continue to take in other poisons from outside in our food, water and air. Put these together, and we literally fall apart, physically AND mentally.