The emerging field of microbiome research offers fascinating, at times disturbing, but ultimately empowering insights into the connection between our gut microbiome, our food choices (which may not be ‘our’ choices, after all) and our moods.
More ‘bug’ than human
The gut microbiome comprises the teeming hordes of bacteria, along with smaller numbers of yeasts, parasites and viruses, which inhabit our gastrointestinal tract. Bacteria outnumber human cells by around 10 to one; a healthy gut microbiome comprises somewhere between 10 to 100 trillion bacteria, of over 1000 different species and more than 7000 strains (species subtypes). Less than 1% of the total DNA found in the human body is actually human. Most of the remainder is bacterial DNA (1).
Who are you feeding?
Different bacterial species have different food preferences. Friendly bacteria or ‘probiotics’ thrive on the fibre and resistant starch that’s left over after we extract the digestible carbohydrate from fruits, vegetables, whole grains and legumes (2). The bacteria ferment these carbohydrates into short chain fatty acids (SCFAs) including propionate, which changes the way our brains perceive energy-dense foods such as cake and ice cream, so that these foods lose their appeal and we eat less of them (3).
These bacteria also ‘repay’ us for feeding them the food they like to eat by releasing neurochemicals that are an exact match for the neurotransmitters that own nerve cells produce.
Various microbial species produce gamma-aminobutyric acid (GABA), a natural tranquilliser; noradrenaline, which is involved in alertness, attention, and memory formation and retrieval; serotonin, the so-called ‘happy hormone’ which not only influences mood, memory, learning, appetite and sleep, but also regulates muscle contraction within the gut; dopamine, which generates feelings of reward; and acetylcholine, which plays key roles in arousal, attention, memory and motivation (4, 5).
Certain beneficial bacteria not only produce but also influence cells in our gut to produce more serotonin (6).
On the other hand, unfriendly or ‘pathogenic’ bacteria thrive on the bile that’s produced when we eat high-fat foods such as chocolate, processed meats and cheese; and undigested protein resulting from a high-protein diet. These bacteria produce chemicals called metabolites which not only raise our risk of bowel cancer (7), but also negatively affect our moods and drive cravings for unhealthy foods (8, 9).
Because bacteria can reproduce so quickly in the ‘right’ conditions, gut bacteria respond incredibly rapidly to what we eat. Just a couple of days on a high-fat diet causes an explosion in the numbers of pathogenic bacteria; and conversely, good bacteria dominate the gut microbiome and bad bacteria numbers drop significantly within days of adopting a very high-fibre plant-based diet (10, 11).
The man (and woman) with two brains
The gut has its own nervous system, called the enteric nervous system (ENS) or ‘gut brain’, which is connected to our ‘main brain’, the central nervous system (CNS) via nerve signals that travel up and down the vagus nerve. Think of the vagus nerve as the Ethernet cable connecting the two brains. In addition, the two brains communicate with each other using hormones, which you might think of as their wireless connection.
Through both the Ethernet and wireless connections, our gut bacteria are able to ‘read’ our emotional state and selectively amplify and prolong certain feelings in order to influence our behaviours in ways that benefit them (12). For example, when people feel down or anxious, they tend to crave sugary and fatty foods, which selectively feed the pathogenic bacteria and starve the fibre-loving probiotic bacteria. Sensing advantage, the bad bugs produce chemicals that keep us feeling sad or stressed for longer, so that we’ll eat more of the food they thrive on, allowing their numbers to expand so that they can dominate the gut microbiome.
The tendency to crave certain foods when feeling particular emotions – both positive and negative – is also affected by gut bacteria, which generate ‘gut feelings’ that are stored in the brain, affecting future decision-making – including decisions about what to eat. So the child who was rewarded for good behaviour with sweets grows into an adult who craves sweets to celebrate their successes; and the emotionally-neglected child who consoled herself by raiding the biscuit jar grows into an adult who stuffs down her unpleasant emotions with sweet and fatty foods. These behaviours feel automatic – beyond our conscious control – because they were ‘programmed’ in very early life by our gut brain.
‘My microbiome made me do it!’
One of the biggest barriers that emotional eaters face when trying to cultivate a healthy relationship with food and eating, is that they don’t understand that ‘their’ food choices are not entirely their own. They feel intense guilt about their cravings for unhealthy foods, which unfortunately often entraps them in a vicious circle of guilt → excessive food restriction → unbearable hunger → bingeing → guilt.
I find that once my clients understand that what they eat selectively feeds either their friendly or pathogenic bacteria, which in turn profoundly affects their moods, they are able to make far better food choices. As one of my clients put it, when she proudly recounted how she was able to head off a craving for chocolate after our discussion about the gut microbiome,
“I realised that it wasn’t me who was craving that chocolate, it was my bad bugs, and I’ll be damned if I’m going to feed those nasty little critters!”
Aside from educating my clients on the connections between what they eat, their gut microbiome, and their emotional state, I use Emotional Freedom Techniques (EFT) and Matrix Reimprinting – energy therapies that allow us to ‘reprogram’ our brain’s automatic, unconscious reactions, including the ones we have to food.
Australian researcher Peta Stapleton has published research demonstrating the effectiveness of EFT, for overcoming food cravings and helping people feel less anxious and more in control of their food choices (13). Dr Stapleton showed that EFT is more effective than cognitive behavioural therapy (CBT) for reducing food cravings and anxiety. EFT can be learned in just minutes, and used easily by everyone from young children to seniors.
I find EFT absolutely invaluable for empowering my clients to head off food cravings when they’re just starting out on their healthy eating journey and have not yet built up their populations of beneficial gut bacteria that help them really enjoy wholesome food. Even more importantly, I use EFT – and in particular, a variant of EFT called Matrix Reimprinting, which involves ‘reworking’ memories of key life incidents to change the negative, limiting beliefs that arose from them – to break the connections between certain mood states and certain foods.