Science Questions

Where does the bacteria in our gut come from?

Sun, 3rd Feb 2008

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James Macaward asked:

We get bacteria in our gut. Where does it come from? Is it from our mums in the womb? Does it come from the environment after weíre born or is it dropped off by the stork?


It will probably surprise you to learn that weíre actually passengers in our own body.

If you count the number of bacteria that live on us an in us there are roughly 50 times as many of them as there are cells in our entire bodies.  There are roughly ten thousand trillion cells in humans so thatís a lot of bacteria. 

Where do they come from?  Well, the answer is when a baby first pops out, assuming it comes the normal way, its first taste of life is quite literally a mouthful of muck.  Itís its mums muck.  Itís bacteria and other debris that are all over the pelvic floor and perineum of the mother.  When the baby comes out those bugs that are there on the mum go into the baby and they get washed down into the stomach and then into the intestine where they take root.

The reason babies can do that and in us most bacteria get killed is because babies donít have much stomach acid at that stage so the bacteria can very easily get in and settle down into the gut.  After a few years they develop and turn into a very unique spectrum which is almost as unique to you as your fingerprint is.  If you come out via a different route, say you have a caesarean then the kinds of bacteria that a baby picks up will be different and thatís been demonstrated.

Because of the spectrum of bacteria being a bit different there can be consequences for your risk of future diseases including things like getting allergies and also having bouts of diarrhoea.  Recent studies have shown that babies born by caesarean section are actually twice as likely in their first year of life to have doses of diarrhoea and to have allergic reactions to things.  Coming out the right way and getting a mouthful of muck unless you absolutely have to come out the wrong way is probably the best way.


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