'Friendly' bacteria help boost happiness
5 April 2007
Scientists have discovered a new way to make people happy - let them eat dirt. 'Friendly' bacteria normally found in soil can help lift our moods and could lead to better treatments for depression in future. Antenna digs in..
Researchers first spotted the special effects of the bacterium, Mycobacterium vaccae, when they used it to help treat patients with lung cancer. They discovered that the bacterium reduced the patient's pain and increased their feelings of well-being.
Lead researcher Dr Chris Lowry explains: 'We thought this might be due to some affect on serotonin in the brain - a chemical that affects happiness. It's a really important chemical and low levels of serotonin can lead to depression in some people.'
Colonies of the bacterium Mycobacterium vaccae were grown in petri dishes in the lab.
Image: Laura Rosa Brunet
Testing their theory out...
'We injected the bacteria into mice and found that it had a very similar effect on them as antidepressant drugs such as Prozac', says Chris Lowry. 'The bacteria were triggering an immune response in the body which somehow led to an increase of serotonin in the brain.
Chris Lowry, an expert in brain science at Bristol University.
Image: Chris Lowry, Bristol University
'This response was really specific. The bacteria were activating groups of nerve cells that produce serotonin in the areas of the brain that regulate mood and brain function, but no where else. This was what was really striking to us - we didn't expect that,' he explains.
The scientists think their results could help unravel why immune system upsets can lead to depression in some people. But before they can put the bacteria to work treating depression, they need to do some more investigations.
This is a section of mouse brain with the nerve cells that make serotonin stained brown. Only the specific nerve cells marked with dark blue areas were activated by the bacteria.
Image: Chris Lowry, Bristol University
'It's possible the bacteria could be added into food and drinks to help patients with depression. Or more likely, we could find out what the exact chemicals are that make the bacteria work and make a new drug to test on patients', says Chris Lowry.
'But before conducting clinical trials on people we need to understand exactly how this works. We believe that the bacteria may trigger sensory nerves in our body that send information back to the brain, causing the increase in serotonin. But at the moment we're really not sure.'
Chocolate helps the brain produce serotonin naturally, but new research could enable scientists to give other foods antidepressant properties.
Other experts agree this could be an important step. 'If you take a drug like Prozac, you are setting off all the serotonin neurons, some of which can cause nasty side effects like insomnia,' says Graham Rook, an expert in Immunology at University College London.
'But this response is very specific and activates just the neurons that affect depression. If you could work out the exact molecular mechanisms by which this bacterium works you could find a whole new way of treating depression.'
Graham Rook, Immunology expert, University College London.
Image: Graham Rook, University College London
'I think these findings are extremely important, particularly in a wider context about hygiene and how it affects our immune system,' he says. 'We need to be sensible about hygiene and realise that letting a child play in the dirt and then come in and take a bun without washing their hands might actually be a good thing to do.'