Can the bacteria in our gut influence our mental health?

by Lynne Malcolm & Olivia Willis for ABC:

A growing number of scientists say yes—and they're warning us not to ignore digestive issues any more.

t's an idea that dates back more than 2,000 years, when renowned Greek physician Hippocrates said that 'all disease begins in the gut'. In fact, up until a couple of centuries ago, the brain and the body were considered an entirely integrated whole.

But with modern medicine's proclivity for reductionism, the two entities have in recent times been seen as mostly distinct from one another.

According to David Perlmutter, author of the New York Times bestselling book Brain Maker, this separation is absurd.

'Brain research in terms of diseases has been focused on the brain all of these years, and really has come up pretty empty-handed when you think about the fact that we have no meaningful treatment for Alzheimer's, autism, Parkinson's and MS.'

Perlmutter says so many issues related to the gut are profoundly influential in the brain, and that a medical revolution is underway to change the way we treat brain-related disorders.

'The really exciting news for me as a brain specialist is the fact that we are now uncovering powerful information in the gut that strongly relates to the health and viability of the brain.'

Boston-based psychiatrist Dr James Greenblatt agrees, and says the workings of our gastrointestinal tract—and the bacteria contained within it—affect our mental health.

'The microbiome is the collection of bacteria in the GI tract, and for years we always thought that our thoughts and our feelings affect our GI tract, so we might get stomach aches or we might get diarrhoea when we are nervous.

'But over the past 20 years or so, we now understand that the gut can affect brain function.'

The amount of bacteria that we harbour in our GI tract is enormous, with more bacteria found in our gut than there are cells in our entire body.

'What we are finding is that this collection of bacteria, this microbiome if you will, has tremendous neurophysiological effects on mood and behaviour and appetite.'

According to Perlmutter, the gut plays a significant role in detoxifying the body by manufacturing vitamins that are critically important to the brain.

'We know the gut, for example, makes more than 90 per cent of very important neurotransmitters, like “the happy chemical”, serotonin,' says Perlmutter.

'What's really exciting is the understanding that the gut and the bacteria that live within the gut regulate the process of inflammation in the human body.'

Inflammation, says Perlmutter, is the 'cornerstone' of virtually every degenerative condition throughout the body.

'Inflammation is what is thought to be operative in Alzheimer's, Parkinson's, autism, coronary artery disease, diabetes, and even cancer.

'So when we understand that inflammation is regulated by the gut, and specifically by the level of good versus bad bacteria that live within the gut, then we suddenly realise that we have got a powerful new area to explore.'

What connects inflammation in the gut to the brain is what scientists refer to as the 'vagus nerve'.

'The gut itself, often called the second brain, is richly, richly innervated with nerves—in what is called the enteric nervous system,' says Perlmutter.

'These two systems communicate instantaneously via electrical cables. So the brain is physically connected to the gut, and it is chemically connected to the gut.'

One of the pathways through which this connection occurs is a chemical in the gut known as LPS, or lipopolysaccharide.

'When it gets through the gut wall when the gut wall isn't functioning appropriately ... when the bacteria are imbalanced or when we've consumed certain foods that challenge the gut lining ... then this LPS gets out and stimulates certain white blood cells,' says Perlmutter.

These white blood cells then go on to create the chemical mediators of inflammation known as cytokines.

'This is a process by which changes in the gut—through this chemical LPS—get out of the gut into the systemic circulation and amp up inflammation.'

According to Perlmutter, it's easy to measure the levels of LPS in patients, and recent peer-reviewed research indicates high levels of LPS in people with Alzheimer's disease, major depressive disorder and autism.

'So we are beginning to see evidence now that these brain-related disorders have something related to the gut that is amping up inflammation.'

If we want to understand what puts the balance of gut bacteria out in the first place, Perlmutter says we needn't look much further than the industrialised societies we live in.

'We realise that when we compare the gut bacteria in rural populations, in non-industrialised places, there is a much richer diversity of bacteria that live there, and various ratios of bacteria we don't see in western cultures.'

Perlmutter says that if we choose to live a 'cosmopolitan lifestyle', we also choose to significantly alter the diversity of bacteria that live within us. Our high carbohydrate, high sugar, low fibre diets may also play a role.

The other big issue? Medication, says Perlmutter.

'Antibiotic usage has a huge role to play in damaging the gut bacteria, and new reports are indicating that the damage that occurs is permanent. And certainly in western cultures we are dramatically overusing antibiotics for every cold and sniffle.'

According to Perlmutter, 75 per cent of the antibiotics produced in America are used to enhance livestock in order to produce products that are ultimately for human consumption.

'We are just beginning to understand that western cultures' microbiome is dramatically different from more rural agrarian populations.

'The only variable here is the modern cosmopolitan lifestyle, and it may well be responsible for the incredible explosion of these degenerative conditions that we are seeing so prevalent in our modern world.'

According to Dr Greenblatt, research into the vast number of bacteria that inhabit our bodies has helped scientists to better understand the increase of autoimmune disorders, allergies and asthma in the community.

'[There are] a whole host of disorders that we now trace back to what we are calling an overly clean environment, erasing all the microbes, and the concept of bacteria being evil villains that we have to wipe out with antibiotics.'

In his book Brain Maker, Perlmutter cites the link between the gut and ADHD to demonstrate how a bacterial imbalance can contribute to brain and behavioural conditions.

'This whole notion of ADHD is relatively new. The connection of ADHD to the gut dates back to some really very interesting research that shows significantly higher levels of ADHD in children who were born by caesarean section.

'How this relates to this discussion is that the process of being born is a very important event in the development of a child's microbiome, because as [he or she] passes through the birth canal, the child picks up all kinds of bacteria from the mother.'

Perlmutter says these bacteria go into the child's nose and mouth and colonise their intestines with 'exactly the right bacteria' they will need to develop their immune system. He says it also assists the child to break down breast milk and food.

'When we deprive children of that, it sets the stage for some very important issues. There is a significant increased risk of ADHD, of autism, of type one autoimmune diabetes, coeliac disease, allergies, and even becoming obese as an adult,' he says.

Perlmutter says early reports on the use of probiotics in the treatment of ADHD are beginning to emerge.

'This is very exciting research that is now being developed where nutritional modulation is having a role to play in what is thought to be, at least in America, a disorder that is fundamentally something that we want to treat with drugs.'

While the brain specialist goes on to emphasise the importance of the microbiome at birth, it is important to note that the research found birth by caesarean section was shown to be a modest risk factor for the development of ADHD, and not the only one.

The use of probiotics, according to Perlmutter, was incorporated into interventional studies dating back a decade ago, when human subjects showed changes in mood after being given specific strains of probiotic bacteria.

He says that in the future, we can expect this research to translate into treatments for depression and anxiety that are not necessarily pharmaceutical, but instead based on manipulating the microbiome.

'It's a far safer way of realising significant changes in physiology, as opposed to treating problems so far down the line—finally looking at the fire, not just the smoke.'

Greenblatt is one of a small number of psychiatrists who's taking into account the state of his patients' GI tracts when treating them for brain and behavioural conditions.

'By looking at some of these [patient's] urine tests and these stool tests to be able to predict which individuals have this imbalance, we have a high success rate of using probiotics,' he says.

Greenblatt admits, however, that giving probiotics to everyone who has a mental health condition is not going to be the answer.

'We're all looking for that silver bullet, but by looking at individual testing there's a percentage of individuals with major psychiatric illness … that completely reversed with these high dose probiotics.'

According to Greenblatt, probiotics research is largely varied and very much in its infancy—with possible clinical applications yet to 'really settle'.

'I think the reality is the research is not quite able to pinpoint that this bacteria [in our GI tract] is good for depression or anxiety or weight loss, but it's clear that there are a couple of things the research has repeatedly shown.'

He says the diversity of the microflora in our gut is 'healthy', and that research has proven the introduction of probiotics into our gut can make a difference in both GI tract function and behaviour.

While being a psychiatrist who treats the gut for mental health issues is unusual, Greenblatt says the scepticism in his field is decreasing. But he's wary more research needs to be done.

'My caution and concern are some of the nutritional supplement companies [say that] based on one small study they have this probiotic that's going to treat depression, another probiotic that's going to treat obesity, another probiotic that's going to regulate cravings.

'I think that's where the caution needs to be heeded, as more and more research needs to be looked at.'

The simple implication, says Greenblatt, is that people need to take care of their gut by being healthy and eating fermented foods that introduce bacteria to the gut on an ongoing basis.

'Taking probiotics is critically important for our overall health,' he says. 'And for those individuals struggling with mental illness, looking to see if some of this overgrowth of clostridia or yeast is in fact a factor can be tremendously helpful.'

Perlmutter shares Greenblatt's optimism for the potential of probiotics in the treatment of brain conditions: 'There is not a robust level of research indicating the effectiveness of probiotics. But I think the exciting part ... is that the door is open to a whole new area that we never conceptualised before.'

Source: http://ab.co/1LoOAji