Bacteria on a plate with red agar

Do ‘good’ and ‘bad’ bacteria exist?

Separate food fibs from food facts

There are approximately 39 trillion bacterial cells in the human body, most of which are found in the gut – meaning that there are as many individual bacteria inside of us as there are actual human cells. The latest techniques for DNA analysis show that these bacteria are much more diverse than anyone suspected, with many different species occupying the same area. In fact, it’s now thought that there are over 10,000 different species of bacteria that live inside humans. This makes it hard to know which are ‘good’ and ‘bad’ bacteria to have, or whether they can be improved by eating live yoghurt, for example.

It is clear that all of them together are important for digestion and for many other aspects of health – and even behaviour. Researchers are now working to understand this ecosystem inside us, called the human microbiome. We already know that its composition is influenced by diet. Some sushi lovers in Japan, for instance, have gut microbes that can digest carbohydrates found in seaweed. It is likely that there are many other subtle adjustments like this yet to be discovered.

Lead image:

Petra B Fritz/Flickr CC BY NC ND


About this resource

This resource was first published in ‘Food and Diet’ in June 2011 and reviewed and updated in August 2016.

Cell biology, Microbiology, Health, infection and disease
Food and Diet
Education levels:
16–19, Continuing professional development