Can gut bacteria affect the brain?Comment on this story
London - Claire Parkinson was desperate to find something to help her young son, Giovanni, cope with his constant digestive gripes, such as painful stomach upsets and wind that had afflicted him since babyhood.
Despite her initial scepticism, Claire, 31, a mother of three from Lewisham, South-East London, decided to try giving Giovanni, who was 11 at the time, a dietary supplement containing probiotic bacteria, having read about their claimed benefits on the internet.
Probiotics are live bacteria which, when consumed, are thought to colonise the stomach with bugs that help digestion. Their beneficial effects are not wholly proven, although there is some evidence they might help with a range of problems, including diarrhoea and food allergies.
Claire says the probiotic supplements quickly made a substantial difference to the frequency and intensity of her son’s tummy upsets.
But something unexpected also happened. The behavioural problems linked to her son’s Asperger’s syndrome were also significantly reduced, she says.
Asperger’s is a form of autism that causes difficulties with communication, interaction and imagination. Asperger’s children may have problems relating to others, and have narrow and repetitive patterns of behaviour and interests.
Claire claims that since taking the probiotics, Giovanni has been less anxious and there have been ‘big improvements’ in his concentration and general behaviour.
Coincidence? Perhaps not. Scientists have long suspected that stomach bacteria may have an effect on how the brain works.
Now, increasingly, studies are providing evidence that the bacteria in the gut may ‘communicate’ with the brain, improving mental health and behaviour in conditions such as anxiety, and possibly even autism and Asperger’s syndrome.
Dr Emeran Mayer, a professor of medicine and psychiatry at the University of California in Los Angeles, has been examining MRI images of the brains of volunteers to see what bearing their gut bugs have on their brains.
In one analysis of 60 people, he found that connections between different regions of the brain differed depending on which type of bacteria was most abundant in the gut.
In another study, where several probiotics were given twice a day to a group of healthy women aged 18 to 55, their anxiety levels were reduced compared to women given a placebo or no treatment.
Brain scans found that the circuits involved in anxiety were not as sensitive, according to his report in the journal Gastroenterology last June.
Dr Kirsten Tillisch, an associate professor of medicine at the University of California, Los Angeles, who worked with Dr Mayer, says: ‘Time and time again, we hear from patients that they never felt depressed or anxious until they started experiencing problems with their gut. Our study shows the gut-brain connection is a two-way street.’
Meanwhile, another researcher, Professor Stephen Collins of McMaster University in Ontario, Canada, colonised the gut bacteria of anxious mice with bacteria from fearless mice. ‘The [anxious] mice became less anxious, more gregarious,’ he reports.
The reverse also worked; bold mice became timid when given the microbes of anxious ones.
Perhaps more controversial is the possible link between gut bacteria and behavioural disorders such as autism.
One report, in the authoritative journal PLOS One, recently speculated that the effect of Western-style diets - high in fat, sugar and salt - on gut bacteria might be contributing to the incidence of autism.
It must be noted that this is only a theory. However, the idea that the carbohydrate-heavy standard Western diet may be a problem is one to which Mayer and Tillisch subscribe - they believe that compared with diets high in vegetables and fibre, the Western diet means fewer beneficial strains of bacteria grow, allowing ‘worse’ gut bacteria to flourish.
Mayer also thinks gut bacteria may even mould the structures of our brains as we grow up and wants to investigate whether giving repeated courses of antibiotics to babies can affect their brains by wiping out beneficial bugs in their tummies.
‘This may have long-term consequences on their development,’ he explains.
There is some preliminary evidence to support this idea. In July, a study by Arizona University’s Biodesign Institute found that a group of autistic children had significantly fewer types of gut microbe than other children.
Our first dose of ‘good’ bacteria should come as a baby passes through its mother’s birth canal. En route, the baby ingests the mother’s vaginal microbes, which begin to colonise the newborn’s gut. The new research suggests that babies may be passed on a poor mix of gut bacteria if their mothers are stressed.
Another study on mice, conducted by the University of Pennsylvania, suggested that pregnant women may transmit the effects of stress to their foetus by way of bacterial changes in the birth canal.
Pregnant mice subjected to stress had remarkably different bacteria in their birth canals than unstressed mothers. A few days after birth, their pups were found to have the same bacterial patterns as their stressed mothers.
But why would the gut bacteria affect the brain? In the stressed mothers’ babies, 20 genes were affected by the reduction in the ‘good’ bacteria, Lactobacillus.
These included genes related to the production of new brain cells and the growth of connections in the brain, according to the research, revealed at the Society for Neuroscience conference in California.
One theory is that the bacteria may interact via the vagus nerve, which runs from the stomach to the brain, and communicates feelings such as hunger and fullness. This nerve may also send sensations of stress to the brain as well.
Other theories include an idea that gut microbes might even produce neurotransmitter chemicals that might somehow influence brain chemistry.
So does that mean we can alter our behaviour by altering our gut bacteria?
Tests on changing human brains via gut microbes are still in their infancy. For example, Dr Faith Dickerson is leading research at the mental health institute at the Sheppard Pratt Health System, in Baltimore, to see if a probiotic can help to prevent relapses of mania among patients suffering from bipolar disorder (previously known as manic depression).
While studies are still in their early stages, Claire Parkinson doesn’t need convincing. She had tried all sorts of things - including fish oils - to try to improve Giovanni’s symptoms.
‘His behaviour in class became so disruptive that we had to take him out of school for months and teach him at home,’ she says.
Claire was initially sceptical about probiotics, but decided to try them out of desperation when all else had failed.
Giovanni has now been taking them for 18 months. He is calmer and ‘certainly has seemed a lot more settled at school’, says Claire, who is also mother to Alice-Sara, ten, and Harley, four.
‘He has even started to do handwriting, which is a miracle. Previously, he would work only at a computer.’
However, the National Autistic Society is adamant that there is no ‘cure’ either for Asperger’s syndrome or autism. - Daily Mail