Bacterial Breakdown

Over 100 trillion beneficial bacteria, viruses and fungi live in the digestive tract. Known collectively as gut microbes, they provide us with nutrients, help us digest, and help us defend against harmful microbes. 

Swallowing microbes

We receive our first microbes at birth and more enter our bodies every day of our lives. They enter through the nose and mouth and travel to the stomach, where conditions are too acidic for many to take up permanent residence. The small intestine is likewise too acidic, but many microbes survive just long enough to move into the colon, where they play a vital role in digestion.

In it together
Although many of the bacteria that get into our bodies are harmful, most of them protect us against microscopic enemies. They do this both by taking up space (lining the intestine walls), and releasing substances that kill harmful bacteria.

Digesting what we can't
The microbes in the colon use the carbohydrates we can't digest for energy. They ferment fibre such as cellulose, which help us absorb dietary minerals such as calcium and iron, are used to produce vitamins, and have other benefits in the body. The microbes themselves also secrete essential vitamins, such as vitamin K.

What's that smell?
Fermentation by gut microbes produces a number of different gases, including hydrogen, carbon dioxide, methane and hydrogen sulphide. In large amounts, these can cause bloating and flatulence. The most gas-producing foods include beans, corn and broccoli - but onions, milk and artificial sweeteners are major offenders, too.



Antibiotics
Antibiotics destroy or slow down the growth of bacteria, but they aren't able to discriminate between harmful and friendly bacteria. As a consequence, the friendly microbes in the gut suffer when we take antibiotics. The diversity of gut bacteria starts to decrease as soon as the antibiotic course starts and reaches a minimum about 11 days later. The populations soon bounce back after treatment, but overuse of antibiotics can cause them permanent damage.


Probiotics
Probiotics are the opposite of antibiotics. They are live bacteria that are consumed - in yoghurts or tablets - to fortify gut bacteria that have been damaged by antibiotics or disease.