Dear Dr. K:  You’ve written about using probiotics to help eczema.  Is there any value for a completely healthy person to take probiotics?

The simple answer to your question is yes.  There are many reasons why the answer is yes, as research on human gut flora is one of the hottest fields in academia right now.

First, a few simple statistics:  The adult human body is composed of about 10-trillion cells, but is colonized by some 100-trillion bacterial cells.  There are about 30,000 bacterial species living in the human GI tract, about 300 species in the mouth, about 100 species living on the skin.

All told, there are only about 100 bacterial species in the world that actually cause disease in humans.  In other words, an overwhelming majority of bacteria are well-behaved and do not make us sick.  Moreover, they may actually help us against the renegade bacteria.  This is certainly true in the GI tract.

Unfortunately, the typical American diet can jeopardize the friendly bacteria.  Many of our food sources contain chemicals and antibiotics that kill the friendly bacteria.  The paucity of fresh fruits and vegetables in the typical American diet – and their replacement by processed foods high in sugars and fat – also negatively impact the gut flora.

Renegade bacteria can learn bad behavior from gut flora.  One example is how Legionella learned to live inside of amoeba.  This led to an adaptive change that allows Legionella to live inside human macrophanges, cells that kind of look like amoeba, but are normally responsible for engulfing and killing bacteria.

Another example is the bacteria H. pylori which causes stomach ulcers, and which, by “criminal association” with other unhealthy GI bacteria has learned to release an enzyme, urease, which blocks the stomach acid that would normally kill the H. pylori.  It also excretes a protein, CagA, that allows it to attach to and enter stomach cells, thus hiding from immune destruction.

However, H. pylori bacteria that haven’t associated with the “criminal element” don’t cause illness.

The bottom line is that the healthier the gut flora, the healthier the individual.  Probiotics are excellent means to this end.