Question: Is good bacteria more common then bad bacteria in somebody's gut?

Ciarán O'Brien answered on 10 Nov 2014:

In most people, yes, if you’re healthy then you’ll mostly have good bacteria in your gut. There are always harmful bacteria in there, but they don’t get much room to grow and do harm because the good bacteria are taking up all the space.

If you get very ill, or you have to take a lot of antibiotics, the bacteria in your gut can die off, leaving space for bad bacteria to spread and cause damage. Clostridium difficile is a good example, it’s found in a lot of healthy people but doesn’t do any harm unless it has space to grow. then it produces toxic chemicals that can quickly poison an unlucky person, and even kill them in a few days.

Sometimes, bacteria that usually help you stay healthy can harm you if their environment changes. They might start producing toxins or invading your cells because a change in their environment forced them to adapt and switch on certain chemical processes to survive, only these new processes end up harming your gut!

It can get very complicated, and we still haven’t figured it all out yet; it’s still impossible to even grow half the bacteria that live in your gut because we don’t know what they feed on, or they need other bacteria present to survive, or they’re just really, really picky about where they’ll grow, so there’s a lot of work still to be done to figure out how they all fit together.

But if you stay healthy and eat properly, you’ll definitely have more good bacteria than bad in your gut and you won’t need to worry about any of that. 🙂